ALBERT

Beschreibung: Das Ca/Mg-Verhältnis wurde auf typischen Kartenausschnitten einer großflächigen geologisch-bodenkundlichen Kartierung auf dem nordfriesischen Festland mit anderen Merkmalen dargestellt und verglichen. Es zeigt keine Beziehungen zu den Sedimentationsbedingungen und damit keine deutbaren Zusammenhänge mit den Kartiereinheiten und den meisten Geländemerkmalen. Dagegen kommt eine deutliche Abhängigkeit von postsedimentären Faktoren heraus, die sich überall anders überlagern und das Ca/Mg-Verhältnis bestimmen. Es ist deshalb als Grundlage für eine Kartierung und Klassifizierung der Marschböden nicht geeignet.

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Beschreibung: Auf drei kleinen benachbarten Moorflächen des Bruchberg-Moores wurden ein durchlaufendes Pollenprofil hergestellt und weitere Untersuchungen nächst der Torfbasis durchgeführt. Anhand der Untergrundmorphologie und der Basisproben konnte die flächenhafte Moorausbreitung rekonstruiert werden. Die ältesten Vermoorungen setzen demnach im Präboreal ein. Unterbrechungen im Moorwachstum wurden am Ende der Waldzeiten VI (älteres Atlantikum) und in VIII b (Subboreal) gefunden.

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Beschreibung: Aus einer detaillierten geomorphologischen Probekartierung (nach GMK 25) im Jungmoränengebiet nördlich des Chiemsees werden die genetisch-chronologischen Probleme der Vorlandfächer des Inn- und Achen (= Chiemsee-) Gletschers in ihrem nördlichen Kontakt-und Wirkungsbereich vorgestellt. Die Darstellung eines phasenhaften Nieder- und Rückschmelzens der würmzeitlichen Vorlandeismassen bestätigt oder differenziert teilweise die bisherigen Untersuchungen, teilweise werden sie aufgrund der Geländebefunde abgelehnt. Am Schluß sind die wesentlichen Ergebnisse thesenartig zusammengefaßt.

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Beschreibung: An drei Orten im nordwestdeutschen Flachlande konnten zwei Interstadiale der Weichseleiszeit festgestellt werden. Vermutlich gehören die Torfe oberhalb des Interglazials von Eversen bei Rotenburg/Hann. ebenfalls einem dieser Interstadiale an (Wolff & Schröder 1940). Die stratigraphischen Verhältnisse lassen eine eindeutige Eingliederung in die Weichselvereisung zu. In allen Fällen liegen die beiden Torfbänke oberhalb des letzten Interglazials und sind in Sanden der letzten Eiszeit eingeschlossen. Von einer Parallelisierung mit den Stadien der Weichselvereisung soll vorläufig Abstand genommen werden. Durch die Pollenanalyse ergab sich eine Unterteilung in eine Birken- und in eine Kiefernphase. Das Klima war subarktisch-ozeanisch. Die Wiedervereisung nach dem letzten Interglazial und den beiden Interstadialen wurde durch ein feucht-kühles, niederschlagsreiches (vermutlich schneereiches) Klima eingeleitet. Beide Interstadiale haben mit der Alleröd-Oszillation gemeinsame Züge, lassen sich jedoch klar von ihr trennen. Ob eine Unterscheidung der beiden Interstadiale mit Hilfe der Pollenanalyse vorgenommen werden kann, ließen die bisherigen Untersuchungen nicht erkennen und muß daher den weiteren Arbeiten vorbehalten bleiben.

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Beschreibung: research

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Beschreibung: Funde nicht-alpiner Gerölle südlich des altpleistozänen Donaulaufs in der östlichen Iller-Lech-Platte werden als umgelagerte Reste pliozäner Donauschotter gedeutet und geben so erste Hinweise auf ein Ausgreifen der Donau 35-40 km südlich ihres heutigen Laufs. Die bisher als Tertiärrelikt angesehene Dinkelscherbener Altwasserscheide dieses Bereichs kann somit erst im Pleistozän entstanden sein und dürfte kaum am Staufenberg vorbei weiter nach NNO gereicht haben.

Beschreibung: research

Beschreibung: Seit 100 Jahren werden Ablagerungen in Norddeutschland als vom Inlandeis hinterlassen angesehen. Der Wechsel der Auffassungen über das Geschehen am Eisrand sowie der heutige Stand der Erkenntnis werden dargelegt. Hervorgehoben wird: Fels- und Lockerboden als Untergrund bedingen verschiedenes Verhalten des Eisrandes. Widerlager wie Stauchmoräne und Hochsander erzwingen das Aufsteigen auch der tiefsten fließenden Eislagen. Schwankungen des Eiszuflusses bedingen Zu- und Abnahme der Mächtigkeit des Eises am Widerlager, aber keine Änderung der Lage des Eisrandes. Bei starkem Zufluß schiebt das Eis das Widerlager beiseite. Die noch jüngst vertretene Anschauung vom „Überfahren" des Widerlagers wird aus mehreren Gründen abgelehnt. — Tunneltäler entstehen durch kleine Eiszungen, die dort auslaufen, wo der Ausfluß in- oder subglazialer Wässer das Widerlager abgetragen hat.

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Beschreibung: Schotterpetrologische Untersuchungen im Aaretal südlich von Bern zeigen, daß die petrologische Zusammensetzung der Fraktion 〉 2 cm von älteren zu jüngeren Schotterakkumulationen gesetzmäßig ändert. Die ältesten, bis jetzt nachgewiesenen pleistozänen Schotter im Aaretal, die Bümbergschotter, sind reich an aufgearbeitetem Mollassematerial (〉15 %), welches in den letzteiszeitlichen Münsingenschottern, bzw. spätglazialen Wichtrachschottern 〈10% beträgt (Abb. 2). Bei den Münsingenschottern (Obere und Untere als Einheit betrachtet) kann östlich und westlich des heutigen Aarelaufes eine verschiedene Fazies in der Geröllführung nachgewiesen werden (Abb. 3). Das von Cadisch (1928) beobachtete Widerspiegeln der Heraushebungs- und Erosionsgeschichte des Alpenkörpers in der Petrologie der Molassesedimente gilt auch für die petrologische Geröllzusammensetzung der mittel- bis jungpleistozänen Schotterakkumulationen.

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Beschreibung: Auf der Grundlage von Tiefenkarten, Lotprofilen und Sedimentechogrammen werden Topographie und Morphologie südwest- und südostgrönländischer Schelfrinnen erfaßt und in ihrer Genese gedeutet. Danach stellen die Schelfrinnen glazial überformte Täler präglazialer Anlage mit geringer mariner Umgestaltung dar. Mündungsschwelle, Moränenumrahmung und ein in Becken und Schwellen gegliedertes Längsprofil weisen die Rinnen als glazial übertiefte Tröge und Gletscherbecken mit Übertiefungsbeträgen von durchschnittlich 275 m aus. Ihre fluviale Anlage fällt in eine Zeit, als die herausgehobenen Kontinentalränder intensiver Abtragung ausgesetzt waren. Die postglaziale marine Sedimentation In den Schelfrinnen ist gering, bedingt durch minimale terrigene Sedimentzufuhr und hohe Fließgeschwindigkeiten des Ost- und Westgrönlandstromes.

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Beschreibung: Die MATUYAMA/BRUNHES-Grenze konnte am Mittelrhein in der Schichtenfolge von Kärlich relativ stark eingeengt werden. Sie ist dort älter als die 6. Eiszeit vor heute und liegt in einer Wechselfolge von Sedimenten, die dem „Ville-Interglazial-Komplex" zugeordnet wird. Möglicherweise muß diese Grenze sogar noch etwas tiefer gelegt werden in einen Horizont mit ersten Zeugnissen eiszeitlichen Dauerfrostbodens. In allen anderen untersuchten Lokalitäten ist die Lückenhafbigkeit der Überlieferung zu groß für detailliertere Aussagen. Die MATUYAMA-Epoche ist vorerst sowohl am Rhein wie an der Donau wegen der vorwiegend gröberklastischen Gesteinsfazies nur bedingt mit der Feingliederung des ältesten Pleistozäns korrelierbar. So sind in der Ville (Tgb. Frechen) mehrere altquartäre warmklimatische Tonhorizonte revers magnetisiert (Tonhorizont B2 und C). Darüber folgt ein normal magnetisierter Horizont (Tonhorizont D), der sich ebenfalls noch im Liegenden der Hauptterrassenfolge befindet. Schließlich wurde neuerdings im Liegenden dieser Abfolge ein weiterer, bereits quartärer Horizont (Bl) gefunden, in welchem sich eine Umpolung von normal nach revers vollzieht. Die Schwierigkeit besteht vorerst noch darin, diese Abfolge geobotanisch genauer zu definieren. Die GAUSS-Epoche läßt sich hingegen in einen guten Zusammenhang mit dem mittleren bis höheren Pliozän bringen (Brunssumium bis mittleres Reuverium). Die Tertiär/Quartär-Grenze auf geobotanischer Grundlage kann nach diesen Befunden etwa mit 2 Mio. Jahre vor heute relativ gut festgelegt werden; denn im höchsten Reuverium (C), das zumeist der Erosion zum Opfer gefallen ist, wurde bereits die Umpolung zur reversen Matuyama-Epodie (Beginn rd. 2,4 Mio. Jahre vor heute) gefunden.

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Beschreibung: Im untersuchten Raum konnte ein Zusammenhang zwischen dem Auftreten ausgedehnter glazial übertiefter Becken und der Ausdehnung aktiver Gletscherzungen gefunden werden. Jene liegen im Zehrgebiet dieser und sind möglicherweise auf die hohe Fließgeschwindigkeit des Eises und dessen starke Anreicherung mit Moränenschutt zurückzuführen. Die Auffüllung der Becken erfolgte sehr rasch im beginnenden Spätglazial und war zur Zeit der Wiederbewaldung bereits abgeschlossen. Dabei kamen petrographische Unterschiede im Einzugsgebiet der Flüsse stark zum tragen.

Beschreibung: research

Beschreibung: Einige mehrgliedrige Lößprofile im Raum der Tagebaue Treue, Helmstedt und Alversdorf der Braunschweigischen Kohlenbergwerke bei Helmstedt werden beschrieben, interpretiert und datiert. In den vollständigen Jungwürm-Profilen lassen sich bis zu vier Naßböden ausgliedern. Eine Parallelisierung mit der Jungwürm-Gliederung von Rohdenburg & Meyer (1966) ist möglich. Erstmals werden aus dem Gebiet am N-Rand der Lößgrenze 1 —1,2 m mächtige Mittelwürmlösse nachgewiesen, die an zwei Lokalitäten (im Tagebau Alversdorf) vom Lohner Boden abgeschlossen werden. Der Altwürmabschnitt weist in den vollständigen Profilen außerhalb von Dellen bis zu 3 Humuszonen bzw. -reste auf, zwischen die Bleichzonen eingeschaltet sind. Der letztwarmzeitliche Boden ist sowohl auf Löß (als Pseudogley oder im oberen Teil pseudovergleyter Bt-Horizont) als auch auf glazifluviatilen und moränalen Ablagerungen entwickelt. Aus den Diskordanzen innerhalb der Profile werden bis zu vier Dellenbildungsphasen und einige weitere Abtragungsphasen abgeleitet.

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Beschreibung: In der Nachbarschaft von Flüssen und größeren Bächen nimmt der Löß sehr häufig eine sandige Beschaffenheit an, in vielen Gebieten ist sogar die Sandkomponente in Form von verschieden starken Schichten (Sandbänder) eingeschaltet. Die vorliegende Arbeit beschäftigt sich in der Hauptsache mit der Lagerung der Sandbänder im vertikalen Profil und mit den Veränderungen in horizontaler Richtung. Auf Grund der allgemeinen Ausbildung und der Körnungsunterschiede des Lößes konnten westlich Königgrätz 4 Faziesbereiche unterschieden werden und zwar die Flugsand-, Bänder-, Übergangs- und Normalfazies. Die 4 Fazieszonen folgen von O nach W aufeinander. Die speziellen Untersuchungen an den Sandbändern führten zu folgenden Ergebnissen: 1. Die Abnahme des prozentualen Anteils der Gesamtmächtigkeit der Sandbänder am Löß erfolgt linear mit dem Logarithmus der Entfernung vom Auswehungsgebiet. 2. Die durchschnittliche Anzahl der Sandbänder je Meter Löß ändert sich mit der Zunahme der Entfernung vom Ursprungsgebiet, wie im einzelnen aus Abb. 10 hervorgeht. 3. Neben der Gesamtmächtigkeit und der Anzahl der Sandbänder wurde auch die Häufigkeit der verschiedenen Mächtigkeitsstufen ermittelt und graphisch aufgetragen (Abb. 11). Dabei ergab sich, daß in unmittelbarer Nähe des Auswehungsgebietes neben wenigen 9 und 10 cm mächtigen Bändern die 2 und 2,5 cm starken überwiegen. In einer Entfernung von etwa 300 m vom Flußufer dominieren die 1 und 1,5 cm starken. Weiter nach W nehmen aber nach und nach die dickeren Lagen wieder zu, so daß am Ende der Sandbänderfazies die 2 und 2,5 cm starken die häufigsten sind. Aus den mitgeteilten Ergebnissen und aus zahlreichen Körnungsanalysen wird geschlossen, daß sowohl die eingelagerten Sandschichten als auch der gößte Teil des Lößes äolischen Ursprungs sind. Sandlagen und Löß wurden durch östliche Winde aus dem breiten Tal der Elbe ausgeweht und auf die benachbarten Höhen transportiert. Dabei gelangte der in Form von Bändern abgelagerte Sand bis zu einer Entfernung von ca. 700 m. Die Kornfeinheit des Lößes nimmt nach W hin immer mehr zu. Weitere Beobachtungen an dem Bystrice- und Cidlina-Tal im W des Untersuchungsgebietes bestätigen die Annahme von der Auswehung des Lößes und der Sandschichten aus den Tälern durch Winde aus östlicher Richtung. Daß die allgemeine Lößverbreitung auch von der Breite der Täler abhängig ist, zeigt ein Blick auf die Karte (Abb. 1).

Beschreibung: research

Beschreibung: Aus einer Höhlenruine werden Kleinsäuger- und Schneckenfaunen qualitativ und quantitativ erfaßt. Ein Komplex gehört in das Würmglazial, die übrigen in das Altholozän, und zwar nach den C14-Datierungen in das Präboreal und frühe Boreal. Altholozäne Kleinsäugerfaunen sind in Süddeutschland durch Pityms subterraneus sowie pleistozäne Reliktformen charakterisiert. In der Gastropodenfauna wird Zebrina detrita in einer reinen Discus ruderatus / Nesovitrea petronella Fauna nachgewiesen.

Beschreibung: research

Beschreibung: Auf Grund geomorphologischer Untersuchungen zur Abfolge der Formungsstadien im Bereich der beiden Flußsysteme Oued Termamane — Oued Zigzaou und Oued En Negueb — Oued El Hallouf — Oued Oum Ez Zessar in der nördlichen Djeffara in Südtunesien lassen sich oberhalb des rezenten Flußbetts neben jüngsten, durch menschliche Eingriffe verursachten Ablagerungen eine aus Feinsedimenten aufgebaute „Jüngere Akkumulation", eine überwiegend aus Grobschottern bestehende „Hauptakkumulation" und nicht sicher zu korrelierende Reste von zumindest zwei älteren, höher gelegenen Niveaus unterscheiden. Die „Hauptakkumulation" ist im gesamten Bereich der genannten Oueds, die „Jüngere Akkumulation" dagegen nur in ihren Mittel- und Unterläufen verbreitet. Letztere fehlt im Hauptverbreitungsgebiet der Schluffe von Matmata (primär äolisch abgelagerte und später fluviatil überformte Sedimente) im Gebirge und am Gebirgsrand. Die Ablagerung der „Jüngeren Akkumulation" ist auf Grund der 14C-Datierung von 2 Holzkohlenproben (Hv 5566 und Hv 5400) in einen Zeitraum etwa zwischen 9000 — 7000 Jahre B.P. zu stellen, die Datierung einer Kalkkruste vom Top der „Hauptakkumulation" ergab ein 14C-Alter von 21385 ± 235 Jahre B.P. (Hv 5402). Auch unter Berücksichtigung der erheblichen Fehlermöglichkeiten dieser Datierung ist ein würmzeitliches oder älteres Alter der „Hauptakkumulation" anzunehmen. Die Schluffe von Matmata überlagern die „Hauptakkumulation" und kommen als Materiallieferant für die Sedimente der „Jüngeren Akkumulation" in Frage; daher ist mit einem würmzeitlichen bis frühholozänen Alter der Schluffe zu rechnen. Hinweise auf im Vergleich zu heute feuchtere klimatische Bedingungen geben eine fossile „Kalkbraunerde" in den Schluffen von Matmata, das Vorkommen von Kalkkrusten und ein Schottertransport zur Zeit der „Hauptakkumulation", der erheblich weiter in das Matmatavorland reichte als der Schottertransport der rezenten Flußbetten.

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Beschreibung: Potential flows may be utilized to represent motions produced in pulsating bulbs. While the initial bulb shape may be arbitrary, sequential shapes are related by affine transformations. Two components appear in the distribution of pressure, one dependent on the instantaneous velocity and the other on the acceleration. For flows with stationary streamlines the inertial impedance is that of a simple mass, and is proportional to the first moment of the actual mass of fluid contained within the bulb. Examples treated are: (1) Expanding and collapsing circular cylinders, and (2) elliptical cylinders in which the perimeter is held constant. The thickness of the pulsatile laminar boundary layer is found to be approximately on millimeter for conditions in the vicinity of the heart. Conditions for separation and turbulence differ from those in steady flow.

Beschreibung: The results of a parametric study on the entrance flow region in a gas core nuclear reactor are presented. The physical system is modeled as laminar confined, coaxial flow with heat generation in the inner fluid. The governing equations include the boundary layer approximations and the assumptions of only radial radiative transport of energy represented as an energy diffusion term. The Von Mises transformation and a zeta transformation are used to transform the equations into nonlinear nonhomogeneous convective-diffusion equations. A unique combination of forward and backward difference equations which yields accurate results at moderate computational times, is used in the numerical method. Results show that the rapidly accelerating, heat generating inner stream actually shrinks in radius as it expands axially.

Beschreibung: The transient response of an elastic cylindrical shell immersed in an acoustic media that is engulfed by a plane wave is determined numerically. The method applies to the USA-STAGS code which utilizes the finite element method for the structural analysis and the doubly asymptotic approximation for the fluid-structure interaction. The calculations are compared to an exact analysis for two separate loading cases: a plane step wave and an exponentially decaying plane wave.

Beschreibung: The inherent tolerance for nuclear radiation makes fluidic devices candidates for nuclear rocket control systems. Also, they are being considered for supersonic jet engine inlet control because of their high temperature and vibration tolerance. Three new control components being considered for these applications are described. A fluidic circuit to control a pneumatic stepping motor for nuclear rocket control drum actuation is discussed. An all-fluidic sensor being developed for determining the position of the normal shock in the inlet of a supersonic jet engine is outlined. A new vortex valve configuration is developed to prevent supersonic jet engine inlet unstarts by regulating bypass flow.

Beschreibung: Calculation procedures for compressible turbulent boundary layers were based upon techniques, modeling constants, etc., developed originally for the low speed case. Significant differences and new or altered physics which occur in the compressible case were considered, as compared with the low speed situation. Possible pitfalls and sources of inaccuracy in the calculations were indicated.

Beschreibung: In the absence of gravity, stirring in a liquid is suppressed because of density differences caused by thermal or compositional gradients. However, other mechanisms resulting in natural convection in a microgravity environment exist. One of the most important mechanisms for liquid metals is surface tension driven convection, which becomes predominant in the low gravity environment. In this case, surface tension differences caused by compositional or temperature gradients have been demonstrated to cause stirring in liquids during experiments performed onboard Skylab. Compositional gradients were created by adding a soap solution to a large water globule, which caused vigorous fluid motion for some moments after the addition.

Beschreibung: This numerical prediction summary indicates the wide variety of such procedures which are available. Most procedures have detailed user manuals, and in many cases the codes are available. Many of the special effects treated by various methods (such as nonequilibrium or equilibrium chemistry, transition, roughness etc.) are indicated.

Beschreibung: From comparisons of high speed data with low speed closure procedures using variable mean density, there does not appear to be any appreciable influence of compressibility upon turbulent shear stress modeling in compressible turbulent boundary layers, even for extreme cases such as Mach 14 to 20 with a change in density across the layer of up to a factor of 100. Other evidence of apparent lack of compressibility caused new physics which may alter the shear stress for the compressible boundary layer cases including: (1) fluctuation Mach number was generally less than 1; (2) the shear stress distribution through the boundary layer was not a function of Mach number for zero pressure gradient flows; (3) the Morkovin hypothesis was valid up to Mach 5 (based on fluctuation data); (4) profile N power was not a function of Mach number, at least up to Mach 10; and (5) the nondimensional burst period was approximately the same as that for low speed.

Beschreibung: Basic differential equations governing compressible turbulent boundary layer flow are reviewed, including conservation of mass and energy, momentum equations derived from Navier-Stokes equations, and equations of state. Closure procedures were broken down into: (1) simple or zeroth-order methods, (2) first-order or mean field closure methods, and (3) second-order or mean turbulence field methods.

Beschreibung: Three demonstrations of scientific concepts concerning liquids were performed during the Apollo-Soyuz Test Project mission. Chemical foaming, spreading of liquids, and capillary wicking were the subjects of each demonstration photographed in space. The results clearly illustrated the basic principles, and films suitable for educational uses are now available from the first author.

Beschreibung: Experiences derived from the development, integration, and flight of NASA spacecraft and sounding rockets are presented. They include the International Heat Pipe Experiment, OAO 3, and ATS-6. Typical flight data are presented to show the performance.

Beschreibung: A theory is proposed for analyzing the inviscid interpretation of two streams in the case when the difference in total pressure between the streams is relatively small. A stream is considered which discharges from a nozzle or reservoir into a partially moving and partially stationary environment in such a way that the flows leave the solid boundaries in a tangential direction where the two streams first interact. The problem is solved by expanding in a small parameter related to the difference in total pressure between the streams, the zeroth-order solution is obtained by classical methods, and a technique similar to that employed in thin-airfoil theory is used to transfer the first-order boundary conditions to the zeroth-order boundary. A procedure is developed to transform the problem into one that can be solved by standard techniques of the theory of sectionally analytic functions. Solutions are obtained for flows with and without free streamlines, and the general theory is applied to several specific flow configurations.

Beschreibung: An approach is presented for applying the net radiation method developed by Siegel and Howell (1972) and Sparrow and Cess (1966) to systems involving opaque and partially transmitting walls. The results obtained from the basic equations for various values of plate emissivities and temperatures are presented in graphs. Attention is given to the window temperature relative to the temperature of the hot wall and the heat transferred relative to that transferred without the window.

Beschreibung: A Green's function formulation is used to derive basic reciprocity relations for planar radiative transfer in a general medium with internal illumination. Reciprocity (or functional symmetry) allows an explicit and generalized development of the equivalence between source and probability functions. Assuming similar symmetry in three-dimensional space, a general relationship is derived between planar-source intensity and point-source total directional energy. These quantities are expressed in terms of standard (universal) functions associated with the planar medium, while all results are derived from the differential equation of radiative transfer.

Beschreibung: Radiation from an array of longitudinal fins of triangular profile is analyzed, including fin-to-fin and fin-to-base interactions. The effect of base cylinder radiation and the fin-base radiative interaction is found to be significant for fin width/tube radius ratios less than 8. Results presented may be used to optimize the design of a fin array with respect to weight.

Beschreibung: An explicit representation for the unsteady motion on a transversely sheared mean flow is obtained which corresponds to the gustline motion on a uniform mean flow. The important features of this motion are discussed. It is shown that its velocity, pressure and vorticity are all induced by a certain disturbance field that is a linear combination of the vorticity and particle-displacement fields and is everywhere frozen in the mean flow. The general ideas are illustrated by considering the scattering of a gust by a half-plane embedded in a shear flow.

Beschreibung: The two-dimensional leveling problem (Degani, Gutfinger, 1976) is extended to three dimensions in the case where the flow Re number is very low and attention is paid to the free surface boundary condition with surface tension effects included. The no-slip boundary condition on the wall is observed. The numerical solution falls back on the Marker and Cell (MAC) method (Harlow and Welch, 1965) with the computation region divided into a finite number of stationary rectangular cells (or boxes in the 3-D case) and fluid flow traverses the cells (or boxes).

Beschreibung: The proposed approach to the derivation of the Navier-Stokes equation is thought to be more plausible and easier to understand than other derivations that can be found in works on fluid mechanics. The tensor character of the stress is central to the derivation. In particular, a linear relation between stress and strain rate is assumed only for the shear, rather than for the full stress tensor as is done in most other derivations. An assumption for the shear is naturally simpler and easier to verify experimentally. The use of tensor analysis is shown to greatly simplify the derivation.

Beschreibung: A critical analysis is given of the applicability of six-beam models to radiative transfer in particulate materials. The method of introducing transverse scattering in these models is shown to cause fundamental difficulties in the case of physically plausible phase functions; in particular, the effective absorptivity is abnormally large and thus results in incorrect reflectances and transmittances. Six-beam calculations for several media are compared with accurate solutions, with Chu-Churchill two-beam results, and with a simple modification to the Eddington approximation, the last being generally superior over a wide range of conditions.

Beschreibung: The stability of the parallel flow of water between concentric cylinders at different temperatures is investigated for infinitesimal velocity and pressure disturbances. Primary interest is in the effect of heat transfer and the radius ratio a/b on the critical point of the neutral stability curve. The results indicate a strong dependence of the critical eigenvalues on both the heat transfer and the radius ratio. The critical Reynolds number of the nonisothermal flow appears to approach a finite value as the inner radius approaches zero (pipe flow) by showing an inflection point on the curve of critical Reynolds number vs a/b.

Beschreibung: Solutions for uniformly-sheared turbulence, in which the interaction of the turbulence with the mean shear dominates the turbulent self-interaction, are compared with experiment. An anisotropic spectral tensor, which appears general enough to represent the initial experimental turbulence, is used for the initial condition in the calculations. The evolution of one-point turbulence components and microscales, as well as two-point velocity correlations, are considered. In most cases the agreement with experiment is good. The theory correctly predicts the presence of a negative region for two-point longitudinal-velocity correlations only for point separations in the direction normal to the flow and the mean gradient.

Beschreibung: An experiment was conducted to determine the varying effects of six different probe-tip and support-shaft configurations on pitot tube displacement. The study was stimulated by discrepancies between supersonic wind-tunnel tests conducted by Wilson and Young (1949) and Allen (1972). Wilson (1973) had concluded that these discrepancies were caused by differences in probe geometry. It is shown that in fact, no major differences in profiles of streamwise velocity over streamwise velocity at boundary-layer edge vs normal coordinate over boundary-layer total thickness result from geometry. The true cause of the discrepancies, however, remains to be discovered.

Beschreibung: Two charts are proposed for calculating the flow coefficient and the area correction factor used in the equation for the flow rate through a sharp-edged orifice. The proposed charts account for variations in the discharge coefficient of sharp-edged orifices and can be used with any pressure ratio for both subcritical and supercritical flow conditions. They can also be used for any gas by using the appropriate gas constant and ratio of specific heats. The application of the charts is illustrated by examples.

Beschreibung: Two-dimensional temperature and heat-flux distributions are calculated for an absorbing-emitting gray medium at radiative equilibrium in a rectangular enclosure. The bounding walls are gray and diffuse with arbitrary surface-temperature distributions, and heat generation may take place inside the medium. As a first approximation, the problem is solved for optically thick systems (differential approximation). These results are subsequently improved by the introduction of a number of geometrical parameters to yield good accuracy for all optical thicknesses. As examples, two cases are discussed in detail: (1) uniform heat generation in a black enclosure, and (2) an enclosure with one gray surface at constant temperature. Comparison with some numerical solutions generated by Hottel's /Hottel and Cohen (1958) and Einstein (1963)/ zonal method shows excellent agreement.

Beschreibung: The steady state laminar motion of a viscous, incompressible and binary fluid is studied for a rotating flow in a cylindrical geometry. The mathematical model employed is a cold flow simulation of the fluid mechanics of the light-bulb concept of the gaseous core nuclear engine. A numerical treatment is developed for the rotating flow which includes a description of the nuclear fuel addition. The problem is formulated with the complete Navier-Stokes equations in order to show the interaction between the fuel addition, the main flow, and the boundary layer flow in an accurate manner. The results presented show holdup of the nuclear fuel for the case of steady fuel addition.

Beschreibung: Adequate prediction techniques for supersonic, mixing, reacting flows are of great importance in the design and performance analysis of supersonic combustion ramjet (scramjet) engines. Analytical programs for parallel injection flow fields with chemical reaction and turbulent mixing are now available for both single and multiple-jet flows. The application of these analyses to simple flow geometries is discussed, and comparisons also are made with data on the more complex case of multiple-jet, reacting flows. A review is given of Langley investigations of parallel injection flow fields. Among these are single-jet studies of nonreacting, turbulent mixing (H2 in air and H2 in N2), and of reacting turbulent mixing (H2 in air) with both single and multiple jets. Implications of the results of the studies for scramjet fuel injector design are discussed.

Beschreibung: A kinetic-theory analysis is made of the flow of a rarefied monatomic gas through a two-dimensional slot connecting two reservoirs. Numerical solutions are obtained by the moment and discrete-ordinate methods. The former method portrays the transition-regime characteristics well but has limitations in the free-molecule regime. The latter method gives accurate results in the free-molecule and slip regimes and bolsters confidence in the accuracy of the transition-regime results. The numerical solution for the mass flux through the slot agrees well with an approximate analytical solution of the moment equations for length-to-width ratios from 6 to 0.5, pressure ratios from 0.8 to 0.1, and Knudsen numbers from 5 to 0.5.

Beschreibung: A numerical program was developed to compute transient laminar flows in two dimensions including multicomponent mixing and chemical reaction. The program can compute both incompressible flows and compressible flows at all speeds, and it is applied to describe transient and steady state solutions for low subsonic, coaxial entry, tue flows. Single component, nonreacting flows comprise most of the solutions, but one steady state solution is presented for trace concentration constituents engaging in a second order reaction. Numerical stability was obtained by adding at each calculation point a correction for numerical diffusion errors caused by truncation of the Taylor series used to finite difference the conservation equations. Transient computations were made for fluids initially at rest, then subjected to step velocity inputs that were uniform across each region of the entry plane and were held constant throughout the computation period. For center tube to annulus velocity ratios of 0.5 and 2.0, the bulk fluid in the tube initially moved in plug flow, but strong radial flows developed near the injection plane which moved the fluid into the high shear region between the jets and away from the tube wall.

Beschreibung: Aspects of pool boiling are considered, taking into account nucleate boiling, the nucleate boiling mechanism, film boiling, and the transition between nucleate and film boiling. The characteristics of two-phase flow are also investigated, giving attention to two-phase flow parameters and equations, the flow pattern in two-phase flow, the pressure drop in two-phase flow, heat transfer in two-phase flow, two-phase flow dynamics, the boiling crisis in two-phase flow, the critical flow rate, the propagation of the pressure pulse and the sonic velocity in two-phase media, instrumentation for two-phase flow, and geometry and field effects on boiling and two-phase flow. Near-critical fluids are also considered.

Beschreibung: It is shown that a previously derived semiempirical equation for describing observed ablation rates of isotropic graphites cannot be applied to low-density flows containing dissociated oxygen. Experimentally determined reaction probabilities of isotropic graphites to molecular and atomic oxygen are used to calculate heat-transfer rates and stagnation-point ablation rates for typical conditions. Integrated mass losses are computed for a group of flight trajectories which start from geosynchronous orbit and enter earth's atmosphere in a skipping motion following near-elliptic decaying orbits. A comparison of the results with those obtained by the equation under question shows excellent agreement for steep trajectories, but large discrepancies for shallow trajectories. The differences are attributed to surface oxidation by atomic oxygen.

Beschreibung: When a flow is forced past an obstacle in a rapidly rotating fluid, a Taylor column forms. This is defined by a set of vertical detached shear layers circumscribing the obstacle which provide the smooth transition from an external inviscid potential flow to a stagnant core above the obstacle. For a hemispherical object, the main adjustment takes place in an external E to the 1/4 power layer and an internal E to the 2/7 power layer; here, the nonlinear flow in these layers is investigated. The problem in the E to the 1/4 power layer is identical to a problem occurring in magnetohydrodynamic flow; in addition, some features of the magnetohydrodynamic problem have been resolved. Numerical solutions are obtained for the steady nonlinear external E to the 1/4 power layer flow up to the point where unsteady flow separation from the Taylor column is imminent. The response of the internal E to the 2/7 power layer to the flow in the E to the 1/4 power layer is calculated, and the results suggest that the internal shear layer is unlikely to play any significant role in the separation process

Beschreibung: On October 4, 1974, the International Heat Pipe Experiment was launched aboard a Black Brant sounding rocket from White Sands, New Mexico. The flight provided six min of near zero gravity during which a total of ten separate heat pipe experiments was performed. The fifteen heat pipes tested represent some of the latest American and European technology. This flight provided the first reported zero gravity data on cryogenic and flat plate vapor chamber heat pipes. Additionally, valuable design and engineering data were obtained on several other heat pipe configurations. The payload and several of its experiments are discussed.

Beschreibung: Experiments in weak-shock dynamics were conducted using a 17-in. diameter shock tube. Weak shocks were generated in air by a compressed nitrogen driver gas; the incident shock waves were brought to a focus by reflecting them from concave cylindrical reflectors at the endwall of the tube. It was found that the behavior of a shock discontinuity at a focus is determined by nonlinear gasdynamic processes. Consideration is also given to nonlinear resonance phenomena, i.e., phenomena associated with oscillatory motion in ducts, with amplitude so large that weak shocks occur. Attention is given to nonlinear resonance in open and closed tubes and to thermal and relaxation effects.

Beschreibung: Drop experiments proposed for Spacelab are discussed and an acoustic chamber utilizing the torques and forces produced by acoustic waves excited within the chamber is described. Its operation and how it is being tested for experiments is discussed.

Beschreibung: The paper presents a theoretical analysis of the thermal boundary layer induced by an isothermal sphere rotating in an otherwise quiescent fluid. The boundary layer is considered to be laminar and compressible, and the effects of buoyancy and viscous dissipation on torque, heat transfer, and the position of the ideal jet (the plane of impingement of the boundary layer from the Northern and Southern Hemispheres) are taken into account.

Beschreibung: A recently developed, potentially high-performance nonarterial wick was extensively tested. This slab wick has an axially varying porosity which can be tailored to match the local stress imposed on the wick. The purpose of the tests was to establish the usefulness of the graded-porosity slab wick at cryogenic temperatures between 110 and 260 K, with methane and ethane as working fluids. For comparison, a homogeneous (i.e., uniform porosity) slab wick was also tested. The tests included: maximum heat pipe performance as a function of fluid inventory, maximum performance as a function of operating temperature, maximum performance as a function of evaporator elevation, and influence of slab wick orientation on performance. The experimental data were compared with theoretical predictions obtained with the GRADE computer program.

Beschreibung: A general fourth order differencing scheme is developed and applied to three viscous test problems to verify the accuracy and applicability of the technique. The procedure is atypical since only three nodes are necessary to obtain the desired fourth order accuracy. This is accomplished by a differencing technique which considers the function and all necessary derivatives as unknowns. The relations for these derivatives yield simple tridiagonal equations which can be easily solved. Comparisons of the fourth order results with those computed using second order methods are presented for the test problems and clearly indicate that the accuracy achieved by these fourth order computations is always significantly better than current second order procedures.

Beschreibung: The present work considers the iterative solution of a coupled set of difference equations and examines methods that carry successive approximates to a state that is invariant with further iteration and independent of the initial guess. Methods are studied with regard to their efficiency and economy of computer resources. The basic principles of classical relaxation are set forth, with attention confined to linear elliptic equations. This discussion involves the evaluation of the spectral radius that is the magnitude of the eigenvalue with largest modulus. The subject of relaxation is then related to the study of ordinary differential equations and hyperbolic partial differential equations. Problems that occur when linearly dependent eigenvectors appear in the relaxation matrix are discussed, leading to multiply connected eigenvalues in the Jordan canonical form. Finally, a brief survey of relaxation methods used in aerodynamics is given.

Beschreibung: A framework is presented for a systematic kinetic theory of turbulence originating from the Liouville equation for the Fourier coefficients of fluid variables. The real and imaginary parts of these Fourier coefficients play the role that particle coordinates (positions and momenta) play in the BBGKY theory. The basic relations of the problem are the incompressible Navier-Stokes equations in two dimensions with zero viscosity, with the probability distributions of Fourier coefficients rather than moments being the basic variables of the theory. A kinetic equation is derived and shown to possess a number of requirements that any reasonable kinetic equation must have: conservation laws, positive-definite spectral densities, and an H-theorem. The major lack in the theory is any reliable information on the relaxation predicted by the complicated linear operator H. Closure of the hierarchy is achieved by the hypothesis that the five-coefficient correlation function is negligible. Problems associated with inclusion of viscosity and external driving forces are discussed.

Beschreibung: In developing computer programs to numerically solve the Navier-Stokes equations, the purpose of the computation must be clearly kept in mind. In the Air Force, the purpose is to provide design information on non-linear aerodynamic phenomenon for aircraft that perform throughout the flight corridor. This translates into the requirement for a computer program which can solve the time averaged compressible Navier-Stokes equations (with a turbulence model) in three dimensions for generalized geometries. The intended application of the results then controls the priorities in addressing critical issues. Recurrent problem areas encountered in the study of viscous flow include: (1) grid generation for arbitrary geometry; (2) numerical difficulties; (3) turbulence models; (4) accuracy and efficiency; and (5) smearing of discontinuities.

Beschreibung: The computational requirements needed for predicting steady viscous flow over complex configurations are considered. The desired predictions must be made at reasonable expense, require a reasonable amount of storage space, and result in solutions that are sufficiently accurate. The data needed to estimate the cost of Navier-Stokes solutions is not available; therefore, experience with the solution of the three-dimensional boundary layers equations are used to illustrate the needed information and what can be expected for the Navier-Stokes solutions.

Beschreibung: All known calculation methods incorporate some sort of turbulence model to reduce the infinite hierarchy of equations, under Reynolds' averaging, to a finite set. All such models suffer from a certain ad hoc nature. A dual structure model was developed wherein the turbulence field is, somewhat arbitrarily, decomposed into large eddies which presumably are dominant contributors to the Reynolds' stress and small eddies which feed on the large eddies as these, in turn feed upon the average flow to gain their energy. These concepts have been developed into a dual approach, one extractive and the other predictive as outlined below.

Beschreibung: A critical analysis of available compliant wall data which indicated drag reduction under turbulent boundary layers is presented. Detailed structural dynamic calculations suggest that the surfaces responded in a resonant, rather than a compliant, manner. Alternate explanations are given for drag reductions observed in two classes of experiments: (1) flexible pipe flows and (2) water-backed membranes in air. Analysis indicates that the wall motion for the remaining data is typified by short wavelengths in agreement with the requirements of a possible compliant wall drag reduction mechanism recently suggested by Langley.

Beschreibung: For the problem of predicting one-dimensional heat transfer between conducting and radiating mediums by an implicit finite difference method, four different formulations were used to approximate the surface radiation boundary condition while retaining an implicit formulation for the interior temperature nodes. These formulations are an explicit boundary condition, a linearized boundary condition, an iterative boundary condition, and a semi-iterative boundary method. The results of these methods in predicting surface temperature on the space shuttle orbiter thermal protection system model under a variety of heating rates were compared. The iterative technique caused the surface temperature to be bounded at each step. While the linearized and explicit methods were generally more efficient, the iterative and semi-iterative techniques provided a realistic surface temperature response without requiring step size control techniques.

Beschreibung: Turbulent shear stress and direct turbulent total heat-flux measurements have been made across a nonadiabatic, zero pressure gradient, hypersonic boundary layer by using specially designed hot-wire probes free of strain-gauging and wire oscillation. Heat-flux measurements were in reasonably good agreement with values obtained by integrating the energy equation using measured profiles of velocity and temperature. The shear-stress values deduced from the measurements, by assuming zero correlation of velocity and pressure fluctuations, were lower than the values obtained by integrating the momentum equation. Statistical properties of the cross-correlations are similar to corresponding incompressible measurements at approximately the same momentum-thickness Reynolds number.

Beschreibung: The phase change coating technique is used to obtain peak heating measurements in shock interference flow regions with high surface shear and heating. This technique provides heat transfer coefficients which are determined by measuring the time for a point on the surface to reach the phase change temperature of the thin fusible coating. Measurements were conducted on a 5.08-cm diameter hemisphere-cylinder made of silica based epoxy at Mach 6 for free stream Reynolds numbers of 3.3 to 25.6 million per meter. A sketch of the shock interference pattern produced by a flat plate shock generator is included. Heating data obtained on a 5.08-cm diameter stainless steel hemispherical model instrumented with thermocouples is presented for the purpose of comparing the phase change technique with the thermocouple-calorimeter technique.

Beschreibung: The laminar free convection flow from a right circular cone with prescribed uniform wall flux condition is studied. The governing boundary-layer equations are analyzed by the technique of similarity transformation. Numerical solutions to the transformed equations are given for Prandtl numbers 0.72, 1, 2, 4, 6, 8, 10, and 100. Expressions for both wall temperature distribution and wall skin friction distribution at Prandtl number tending to infinity are also presented.

Beschreibung: Although the goals and techniques of computational aerodynamics and computational fluid dynamics differ, advancement in the physical and mathematical aspects of the latter are required for progress in aerodynamic computation. The most attractive approach is the use of hybrid methods where both the equations treated and the solution algorithms reflect the local character of the flow. A working general turbulence model that is only peripherally related to the availability of large fast computers would provide a significant breakthrough in computational aerodynamics. There is no unanimity of opinion as to what may be the optimum algorithm or family of algorithms in the next decade. While it is premature to develop an optimum processor, such a machine dedicated to study the structure of solutions to the three-dimensional time-dependent Navier-Stokes equations and to the computability of turbulence would be very valuable.

Beschreibung: Although significant advances have been made in the simulation of two-dimensional compressible laminar viscous flows by numerically solving the compressible Navier-Stokes (N.S.) equations, problem areas still remain to be solved before viscous flows requiring solution of the compressible N.S. equations can be efficiently and accurately simulated for flows of aerodynamic interest. These problem areas include turbulence (three-dimensional character), complex geometry, flow unsteadiness, placement of artificial boundaries relative to solid boundaries, specification of boundary conditions, and large flow gradients near surfaces and in the vicinity of shock waves for supersonic flows.

Beschreibung: The problem of designing the wing-fuselage configuration of an advanced transonic commercial airliner and the optimization of a supercruiser fighter are sketched, pointing out the essential fluid mechanical phenomena that play an important role. Such problems suggest that for a numerical method to be useful, it must be able to treat highly three dimensional turbulent separations, flows with jet engine exhausts, and complex vehicle configurations. Weaknesses of the two principal tools of the aerodynamicist, the wind tunnel and the computer, suggest a complementing combined use of these tools, which is illustrated by the case of the transonic wing-fuselage design. The anticipated difficulties in developing an adequate turbulent transport model suggest that such an approach may have to suffice for an extended period. On a longer term, experimentation of turbulent transport in meaningful cases must be intensified to provide a data base for both modeling and theory validation purposes.

Beschreibung: The underlying bases and developments in two techniques of detailed turbulence modeling are described where the flow is treated in the Eulerian sense, and one technique where the Lagrangian motions of vortices are followed. First, a technique is described for solving the single-point statistically averaged conservation equations. The Reynolds stresses that appear in these equations are evaluated by solving supplemental differential equations which contain terms that are modeled. A sequence of increasingly complex, but also increasingly general, modeling equations is described and computations based on these equations are compared with experimental data. The hierarchy of models described terminates with equations for the individual components of the Reynolds stress tensor. The second Eulerian technique approach to turbulence modeling is the direct numerical simulation of turbulent fields. In this approach, all three dimensional eddies between a predetermined range of sizes are computed in time within a specified volume of flow. Present day computers require a tradeoff between the size of the volume that can be considered and the degree of resolution of the turbulent eddies. Techniques of modeling the smallest eddies are described that permit enlarging the volume, or Reynolds number, that can be considered.

Beschreibung: The paper describes a theoretical investigation of the stability under gravitational and surface forces of a liquid in a circular cylindrical container with a concave spheroidal bottom for the case in which the volume of the liquid is sufficiently small so that the bottom is not covered completely. The gravitational field is assumed to be directed along the symmetry axis of the container, and for a specific container shape the critical Bond number is calculated as a function of liquid volume for contact angles of gamma = 0, 1, 2, and 4 deg. For gamma = 0 deg, some critical equilibrium configurations and corresponding perturbation modes are presented.

Beschreibung: The presented review is concerned with the problem of calculating compressible viscous flows. Basic numerical considerations and problems associated with calculating viscous flows are examined and current numerical approaches toward the solution of the Navier-Stokes equations are discussed. It is pointed out that the numerical solution of the full time-dependent equations for turbulent flow is not practical with present computers. Therefore, turbulence effects must be accounted for by modeling. Developments related to turbulence modeling are described. In connection with a discussion of numerical methods for solving viscous flow equations, attention is given to numerical domains of dependence of typical explicit and implicit methods, the diffusion problem, the convection-diffusion problem, and the split-hybrid method.

Beschreibung: Steady state solutions to two time dependent partial differential systems have been obtained by the Method of Lines (MOL) and compared to those obtained by efficient standard finite difference methods: (1) Burger's equation over a finite space domain by a forward time central space explicit method, and (2) the stream function - vorticity form of viscous incompressible fluid flow in a square cavity by an alternating direction implicit (ADI) method. The standard techniques were far more computationally efficient when applicable. In the second example, converged solutions at very high Reynolds numbers were obtained by MOL, whereas solution by ADI was either unattainable or impractical. With regard to 'set up' time, solution by MOL is an attractive alternative to techniques with complicated algorithms, as much of the programming difficulty is eliminated.

Beschreibung: Experimental results show conclusively that the presence of a small quantity of a noncondensable gas (NCG) mixed with the working fluid has a considerable effect on the condensation process in a rotating heat pipe. The temperature distribution in the condenser shows the blanketing effect of the NCG and the ratio of the molecular weight of the working fluid to that of the NCG has a very definite effect on the shape of this distribution. Some of the effects are quite similar to the well-established data on stationary heat pipes.

Beschreibung: Experimental evidence shows the importance of external boundary conditions on the overall performance of a rotating heat pipe condenser. Data are presented for the boundary conditions of constant heat flux and constant wall temperature for rotating heat pipes containing either pure vapor or a mixture of vapor and noncondensable gas as working fluid.

Beschreibung: The turbulence generated by random entropy fluctuations in an accelerating stream is analyzed. The results are obtained by using rapid distortion theory together with a high frequency solution of a previously developed wave equation that governs the small-amplitude unsteady vortical and entropic motion on steady potential flows (Goldstein, 1978). Simple results are obtained for the case of symmetric contraction, expansion or combination of the two. It is shown that the energy of the entropy-generated turbulence increases more rapidly with the contraction ratio of a subsonic flow than that of any imposed upstream turbulence. This result indicates that the entropy-generated turbulence may be more significant than the hydrodynamically generated turbulence in the turbine stages of aircraft engines.

Beschreibung: On the basis of this investigation of the high-temperature behavior of polytetrafluoroethylene (PTFE), the transient one-dimensional ablation of PTFE has been developed by taking into account the optical transmittance of both the amorphous zone and the crystalline zone of PTFE layer. Results show that although the exposed surface receded at an apparently steady state, both the internal temperature and the thickness of the gel layer increase continuously due to the internal absorption of radiation.

Beschreibung: It is shown that the pressure and velocity fluctuations of the unsteady motion on a transversely sheared mean flow can be expressed entirely in terms of the derivatives of two potential functions. One of these is a convected quantity that can be specified as a boundary condition and is related to a transverse component of the upstream velocity field. The other can be determined by solving an inhomogeneous wave equation whose source term is also a convected quantity that can be specified as a boundary condition in any given problem. The general theory is used to study the interaction of an unsteady flow with a semi-infinite plate embedded in a shear layer. The acoustic field produced by this interaction is calculated in the limits of low and high frequency. The results are compared with experimental one-third octave sound pressure level radiation patterns. The agreement is found to be excellent, especially in the low frequency range, where the mean-flow and convective effects are shown to have a strong influence on the directivity of the sound.

Beschreibung: Surface water waves generated by surface and near surface point explosions are calculated. Taking the impulse distribution imparted at the water surface by the explosion as the overriding mechanism for transferring energy of the explosive to surface wave motion, the linearized theory of Kranzer and Keller is used to obtain the wave displacement in the far field. The impulse distribution is obtained by integrating the pressure wave over an appropriate time interval on a horizontal surface just beneath the undisturbed water surface. For surface explosions, a modified form of the similarity method first used by Collins and Holt is used to obtain the flow field. In the case of submerged explosions, the flow field is estimated by making necessary modifications to Sedov's similarity solution to account for the venting that accompanies the interaction of the leading (blast) wave with the ocean surface. Surface waves generated by a charge at six depths of placement (0.15 m, 0.30 m, 0.61 m, 0.91 m, 1.37 m, 3.05 m) are considered in addition to surface explosions. The results seem to support the existence of an upper critical depth phenomenon (of the type already established for chemical explosions) for point (nuclear) explosions.

Beschreibung: Compressible Navier-Stokes equations for quasi-one-dimensional flow in a converging-diverging nozzle have been solved using Stetter's three-step predictor-corrector technique. Particular emphasis is given to the minimum iterative step feature for steady-state solutions. It is found that for the nonviscous-dominated case, Stetter's method attains the steady-state solution in the fewest steps when compared to four other currently used techniques.

Beschreibung: Predictions of mixing length by Pletcher's (1976) method (using a two-layer eddy viscosity model for a turbulent boundary layer at low Reynolds numbers) are compared to some values derived from turbulent boundary-layer profiles by other authors. The model is incorporated into a finite-difference scheme, to accurately predict low Reynolds number skin friction in supersonic flow.

Beschreibung: The use of hot-wire anemometry for obtaining fluctuating data in transonic flows has been evaluated. From hot-wire heat loss correlations based on previous transonic data, the sensitivity coefficients for velocity, density, and total temperature fluctuations have been calculated for a wide range of test conditions and sensor parameters. For sensor Reynolds number greater than 20 and high sensor overheat ratios, the velocity sensitivity remains independent of Mach number and equal to the density sensitivity. These conditions were verified by comparisons of predicted sensitivities with those from recent direct calibrations in transonic flows. Based on these results, techniques are presented to obtain meaningful measurements of fluctuating velocity, density, and Reynolds shear stress using hot-wire and hot-film anemometers. Example of these measurements are presented for two transonic boundary layers.

Beschreibung: The accretion of rotating gas on to a gravitating object is investigated by means of a perturbation to the spherically symmetrical flow. An expression is found for the correction to the accretion rate due to rotation of the gas in terms of the boundary conditions far from the object. In the case of accretion from a cloud with uniform angular velocity, the gas is accreted preferentially from a 'jet' near the axis of rotation. The angular-momentum distribution in the cloud can be altered by the propagation of inertia waves.

Beschreibung: An iterative method for numerically solving the time independent Navier-Stokes equations for viscous compressible flows is presented. The method is based upon partial application of the Gauss-Seidel principle in block form to the systems of the nonlinear algebraic equations which arise in construction of finite element (Galerkin) models approximating solutions of fluid dynamic problems. The continuous cubic element on triangles is employed for function approximation. Computational results for a free shear flow at Re = 1000 indicate significant achievement of economy in iterative convergence rate over finite element and finite difference models which employ the customary time dependent equations and symptotic time marching procedure to steady solution. Numerical results are in excellent agreement with those obtained for the same test problem employing time marching finite element and finite difference solution techniques.

Beschreibung: An analysis of condensation problems in rotating heat pipes containing vapors with different concentrations of non-condensable gases is given. In situations such as this, temperature and concentration gradients are set up in the vapor-gas mixture. There is a transport of mass due to temperature gradients accompanied by an energy transport phenomena due to a concentration gradient. A Nusselt type analysis is not suited to this type of problem; however, a boundary layer type approach has successfully been used to analyze stationary condensation systems with non-condensable gases present. The present boundary layer analysis is presented for condensation processes on the inside of a rotating heat pipe in the presence of non-condensable gases.