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  • 1
    Electronic Resource
    Electronic Resource
    Prediction of the steady surface thermal plume (1983)
    Springer
    Heat and mass transfer 17 (1983), S. 193-200 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Dieser Bericht beschreibt ein zweidimensionales Rechenverfahren, das mit Hilfe Finiter-Differenzen-Techniken die partiellen Differentialgleichungen, welche das Geschwindigkeits- und Temperaturfeld stationärer Oberflächenauf-triebsstrahlen beschreiben, löst. Die Verteilungen der Geschwindigkeit und Temperatur in der vertikalen Richtung werden als ungefähr konstant betrachtet. Die durch die Turbulenz bedingten Einmischraten des umgebenden Fluids werden aus empirischen Beziehungen bestimmt, die den Auftriebseinfluß in bezug auf das Abdämpfen der Turbulenzbewegung berücksichtigen. Berechnungen der Quer- und Längsprofile der Geschwindigkeiten und Temperaturen sowie die Schichtdicke werden mit Labormessungen verglichen; die densimetrischen Froude-Zahlen bewegen sich im Bereich von. 1...4 und das anfängliche Höhen-zu-Breiten-Verhältnis der Austrittsöffnung variiert zwischen 1 und 3. Die Übereinstimmung zwischen Messung und Rechnung ist in der Mehrzahl der Testfälle gut.
    Notes: Abstract This paper presents a two-dimensional numerical procedure which employs finite-difference techniques to solve the partial-differential equations governing the steady flow and heat transfer of a surface thermal plume in the near field. The profiles of the velocities and temperature are assumed to be nearly uniform in the vertical direction. The rates of turbulent entrainment of ambient fluid are calculated from empirical relations, which take the influence of buoyancy in damping turbulent fluctuations into consideration. Computations of the lateral and longitudinal profiles of the velocities, temperature and layer depth are compared with laboratory measurements in heated discharges at densimetric Froude numbers in the range 1–4 and initial aspect ratios varying from 1 to 3. The agreement between the computations and the measurements is fairly good in most cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01002362
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Prediction of the steady surface thermal plume in crossflow (1985)
    Springer
    Heat and mass transfer 19 (1985), S. 41-46 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Dieser Bericht beschreibt ein zweidimensionales Rechenverfahren, das mit Hilfe Finiter-Differenzen-Techniken die partiellen Differentialgleichungen löst, welche das Geschwindigkeits- und Temperaturfeld stationärer Oberflächenauftriebsstrahlen über einer querströmenden umgebenden Flüssigkeit beschreiben. Ein früheres Modell, entwickelt für die Berechnung von Auftriebsstrahlen in stehenden Umgebungen, wurde durch Einfügung von Krümmungseffekten in den Impulsgleichungen erweitert. Eine Integralgleichung wurde ebenfalls gelöst, um den Bahnverlauf der Auftriebsstrahlen zu bestimmen. Vergleiche der vorgestellten Modellrechnungen mit zwei experimentell bestimmten Datensätzen zeigen, daß sowohl die Mittellinienbahnverläufe als auch die Geschwindigkeits- und Temperaturverläufe gut berechnet wurden.
    Notes: Abstract This paper presents a two-dimensional numerical procedure which employs finite-difference techniques to solve the partial-differential equations governing the steady flow and heat transfer of a surface thermal plume above a crossflowing ambient fluid in the near field. An earlier model developed for predicting thermal plumes in stagnant surroundings is extended by the inclusion of curvature terms in the momentum equations. An integral equation is also solved to determine the trajectory of the thermal plume. Comparisons of present model calculations with two sets of experimental data show that the centre-line trajectories as well as the velocity and temperature decays are well predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01682545
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  • 3
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    Prediction of the steady surface thermal plume in crossflow (1985)
    Springer
    Details
    Publication Date: 1985-03-01
    Print ISSN: 0042-9929
    Electronic ISSN: 1432-1181
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 4
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    Prediction of the steady surface thermal plume (1983)
    Springer
    Details
    Publication Date: 1983-12-01
    Print ISSN: 0042-9929
    Electronic ISSN: 1432-1181
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 5
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    Calculation of turbulence-driven secondary motion in non-circular ducts (1984)
    Cambridge University Press
    Details
    Publication Date: 1984-03-01
    Description: Experiments on and calculation methods for flow in straight non-circular ducts involving turbulence-driven secondary motion are reviewed. The origin of the secondary motion and the shortcomings of existing calculation methods are discussed. A more refined model is introduced, in which algebraic expressions are derived for the Reynolds stresses in the momentum equations for the secondary motion by simplifying the modelled Reynolds-stress equations of Launder, Reece & Rodi (1975), while a simple eddy-viscosity model is used for the shear stresses in the axial momentum equation. The kinetic energy k and the dissipation rate ε of the turbulent motion which appear in the algebraic and the eddy-viscosity expressions are determined from transport equations. The resulting set of equations is solved with a forward-marching numerical procedure for three-dimensional shear layers. The model, as well as a version proposed by Naot & Rodi (1982), is tested by application to developing flow in a square duct and to developed flow in a partially roughened rectangular duct investigated experimentally by Hinze (1973). In both cases, the main features of the mean-flow and the turbulence quantities are simulated realistically by both models, but the present model underpredicts the secondary velocity while the Naot-Rodi model tends to overpredict it. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 6
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    Calculation of flow and pollutant dispersion in meandering channels (1986)
    Cambridge University Press
    Details
    Publication Date: 1986-11-01
    Description: Experiments on and calculation methods for flow and pollutant spreading in meandering channels are reviewed. The shortcomings of existing calculation methods are discussed in the light of the complex three-dimensional nature of the flow situation. A mathematical model is presented which takes full account of the three-dimensionality of the flow and pollutant concentration fields. This model is based on the solution of the momentum equations governing the flow in the lateral, vertical and longitudinal directions with a three-dimensional numerical procedure together with the continuity equation. The turbulent stresses appearing in the momentum equations are calculated with a version of the k-ε turbulence model that accounts for streamline curvature effects on turbulence. The pollutant concentration field is subsequently obtained from a solution to its transport equation. The model is tested by application to three different meander situations for which velocity and concentration measurements are available from the literature, with channel width-to-depth ratios in the range 4–20, smooth and rough beds and various pollutant-discharge locations. Detailed comparisons of the velocity and concentration fields show generally good agreement. The effect of streamline curvature on the turbulent mass fluxes was found to be important only in the narrow channel with a smooth bed. Bed-generated turbulence appears to overrule this in the other two cases of a wide channel with a smooth bed and a narrow channel with a rough bed. The flow patterns show the presence of a single large eddy at most cross-sections in these cases, whereas the predictions indicate the presence of usually more than one eddy in the former case. © 1986, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 7
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    Application of multi-grid methods for solving the Navier-Stokes equations (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: This paper presents the application of a class of multi-grid methods to the solution of the Navier-Stokes equations for two-dimensional laminar flow problems. The methods consists of combining the full approximation scheme-full multi-grid technique (FAS-FMG) with point-, line- or plane-relaxation routines for solving the Navier-Stokes equations in primitive variables. The performance of the multi-grid methods is compared to those of several single-grid methods. The results show that much faster convergence can be procured through the use of the multi-grid approach than through the various suggestions for improving single-grid methods. The importance of the choice of relaxation scheme for the multi-grid method is illustrated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Institution of Mechanical Engineers, Proceedings, Part C - Journal of Mechanical Engineering Science (ISSN 0954-4062); 203; C4, 1; 255-265
    Format: text
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  • 8
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    Role of pressure diffusion in non-homogeneous shear flows (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A non-local model is presented for approximating the pressure diffusion in calculations of turbulent free shear and boundary layer flows. It is based on the solution of an elliptic relaxation equation which enables local diffusion sources to be distributed over lengths of the order of the integral scale. The pressure diffusion model was implemented in a boundary layer code within the framework of turbulence models based on both the kappa-epsilon-(bar)upsilon(exp 2) system of equations and the full Reynolds stress equations. Model computations were performed for mixing layers and boundary layer flows. In each case, the pressure diffusion model enabled the well-known free-stream edge singularity problem to be eliminated. There was little effect on near-wall properties. Computed results agreed very well with experimental and DNS data for the mean flow velocity, the turbulent kinetic energy, and the skin-friction coefficient.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases. 5: Proceedings of the 1994 Summer Program; p 313-321
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    On modeling pressure diffusion in non-homogeneous shear flows (1996)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: New models are proposed for the 'slow and 'rapid' parts of the pressure diffusive transport based on the examination of DNS databases for plane mixing layers and wakes. The model for the 'slow' part is non-local, but requires the distribution of the triple-velocity correlation as a local source. The latter can be computed accurately for the normal component from standard gradient diffusion models, but such models are inadequate for the cross component. More work is required to remedy this situation.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: Studying Turbulence Using Numerical Simulation Databases; Part 6; 63-72; NASA-TM-111953
    Format: application/pdf
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  • 10
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    The present status and future direction of algebraic Reynolds stress models: Comment on (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: A number of algebraic stress models are presented and evaluated. These models are then compared to each other as well as to experimental data for three different flow conditions. Finally, the limitations of the models are examined in the presence of curvature, rotation/swirl, gravitation/body forces, and streamwise corners. All results are presented in viewgraph format.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Workshop on Engineering Turbulence Modeling; p 145-159
    Format: text
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