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  • FLUID MECHANICS AND HEAT TRANSFER  (7)
  • INSTRUMENTATION AND PHOTOGRAPHY
  • STRUCTURAL MECHANICS
  • 2005-2009
  • 1990-1994  (11)
  • 1980-1984
  • 1990  (11)
  • 1
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    Long-wave morphological instabilities in the directional solidification of a dilute binary mixture (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Long-wave instabilities in a directionally-solidified binary mixture may occur in several limits. Sivashinsky (1983) identified a small-segregation-coefficient limit and obtained a weakly nonlinear evolution equation governing subcritical two-dimensional bifurcation. Brattkus and Davis (1988) identified a near-absolute-stability limit and obtained a strongly nonlinear evolution equation governing supercritical two-dimensional bifurcation. The present investigation identifies a third strongly nonlinear evolution equation, arising in the small-segregation-coefficient, large-surface-energy limit. This equation links both of the former and describes the change from the sub- to super-critical bifurcations. This study sets the previous long-wave analyses into a logical framework.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: SIAM Journal on Applied Mathematics (ISSN 0036-1399); 50; 420-436
    Format: text
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  • 2
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    Hydrodynamic interactions in directional solidification (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A binary liquid undergoes unidirectional solidification. The one-dimensional steady state is susceptible to morphological instability that causes the solid/liquid interface to change from a planar state to a cellular pattern. This paper examines the effects on this transition of volume-change convection, buoyancy-driven convection or forced flows. It emphasizes how flows alter stability limits, create scale and pattern changes in morphology, and create, through coupling, new instabilities. Emphasis is placed on the physical mechanisms of the interactions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 212; 241-262
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  • 3
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    Long-wave interactions in morphological and convective instabilities (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A binary liquid that undergoes directional solidification is susceptible to morphological and solutal-convective instabilities that cause the solid/liquid interface to change from a planar to a cellular state. This paper gives derivations for those long-wave evolution equations that describe the weak couplings between convection and interface morphology and gives some analytical results obtainable from these.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: IMA Journal of Applied Mathematics (ISSN 0272-4960); 45; 3, 19; 267-285
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  • 4
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    A parametric shell analysis of the shuttle 51-L SRB AFT field joint (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Following the Shuttle 51-L accident, an investigation was conducted to determine the cause of the failure. Investigators at the Langley Research Center focused attention on the structural behavior of the field joints with O-ring seals in the steel solid rocket booster (SRB) cases. The shell-of-revolution computer program BOSOR4 was used to model the aft field joint of the solid rocket booster case. The shell model consisted of the SRB wall and joint geometry present during the Shuttle 51-L flight. A parametric study of the joint was performed on the geometry, including joint clearances, contact between the joint components, and on the loads, induced and applied. In addition combinations of geometry and loads were evaluated. The analytical results from the parametric study showed that contact between the joint components was a primary contributor to allowing hot gases to blow by the O-rings. Based upon understanding the original joint behavior, various proposed joint modifications are shown and analyzed in order to provide additional insight and information. Finally, experimental results from a hydro-static pressurization of a test rocket booster case to study joint motion are presented and verified analytically.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-102748 , NAS 1.15:102748
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  • 5
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    Experimental investigation of turbulent flow through a circular-to-rectangular transition duct (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An incompressible, turbulent, swirl-free flow through a circular-to-rectangular transition duct was studied experimentally. The cross-sectional geometry all along the duct was defined using the equation of a superellipse. The three mean velocity components and the six Reynolds stress components were measured at two axial stations downstream from the transition. It is shown that a secondary flow vortex pair which develops along the duct sidewalls significantly distorts the mean and turbulence fields. At the duct exit, the flow is not in local equilibrium, but recovers to local equilibrium conditions in the rectangular extension duct. Analysis demonstrates that conventional wall functions are not applicable at all streamwise locations in the duct.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-1505
    Format: text
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  • 6
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    Device for quickly sensing the amount of O2 in a combustion product gas (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A sensing device comprising an O2 sensor, a pump, a compressor, and a heater is provided to quickly sense the amount of O2 in a combustion product gas. A sample of the combustion product gas is compressed to a pressure slightly above one atmosphere by the compressor. Next, the heater heats the sample between 800 C and 900 C. Next, the pump causes the sample to be flushed against the electrode located in O2 sensor 6000 to 10,000 times per second. Reference air at approximately one atmosphere is provided to the electrode of O2 sensor. Accordingly, the O2 sensor produces a voltage which is proportional to the amount of oxygen in the combustion product gas. This voltage may be used to control the amount of O2 entering into the combustion chamber which produces the combustion product gas.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 7
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    Unsteady analysis of hot streak migration in a turbine stage (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Two- and three-dimensional Navier-Stokes analyses are used to predict unsteady viscous rotor-stator interacting flow in the presence of a combustor hot streak. Predicted results are presented for a two-dimensional three-stator/four-rotor, a two-dimensional one-stator/one-rotor, and a three-dimensional one-stator/one-rotor simulation of hot streak migration through a turbine stage. Comparison of these results with experimental data demonstrates the capability of the three-dimensional procedure to capture most of the flow physics associated with hot streak migration including the effects of combustor hot streaks on turbine rotor surface temperatures. It is noted that blade count ratio has little effect on predicted time-averaged surface pressure and temperature distributions, but a substantial effect on the unsteady flow characteristics. It is shown that high-temperature hot streak fluid accumulates on the pressure surface of the rotor blades, resulting in a high time-averaged surface temperature 'hot spots'.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-2354
    Format: text
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  • 8
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    Determination of cloud optical depth with the multiple field of view sun photometer (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An approach to determining cloud optical depth is presented which utilizes a multiple-field-of-view sun photometer, along with modeled behavior of transmittance ratios as a function of the field of view, to infer the optical depth. The data used in the analysis were collected during the FIRE Stratocumulus IFO, which took place from July 15 to 17, 1987. Values which were taken within an hour of local solar noon are presented and compared with the values computed for mu sub 0 = 1.0. The zenith angle for the measurements was between 11 and 18 deg. It is found that this method of inferring the optical depth indicates most clouds with optical depths within these limits. The measured curves have a slightly different shape than do the modeled ratios.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Conference on Atmospheric Radiation; Jul 23, 1990 - Jul 27, 1990; San Francisco, CA; United States
    Format: text
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  • 9
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    On the buoyancy-driven motion of a drop towards a rigid surface or a deformable interface (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The deformation of a viscous drop, driven by buoyancy toward a solid surface or a deformable interface, is analyzed in the asymptotic limit of small Bond number, for which the deformation becomes important only when the drop is close to the solid surface or interface. Lubrication theory is used to describe the flow in the thin gap between the drop and the solid surface or interface, and boundary-integral theory is used in the fluid phases on either side of the gap. The evolution of the drop shape is traced from a relatively undeformed state until a dimple is formed and a long-time quasi-steady-state pattern is established. A wide range of drop to suspending phase viscosity ratios is examined. It is shown that a dimple is always formed, independently of the viscosity ratio, and that the long-time thinning rates take simple forms as inverse fractional powers of time.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 217; 547-573
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  • 10
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    Experimental investigation of a single flush-mounted hypermixing nozzle (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The results of an experimental wind tunnel investigation of a circular supersonic jet (m sub j = 3.47) injected at a 10 degree angle into a supersonic freestream. The jet penetrates a boundary layer, which has a thickness approximately the same as the jet nozzle exit diameter. Measurements were made for nominal freestream Mach numbers of 1.6, 2.0, 2.5, and 3.0. Three jet total pressures were run at each freestream Mach number, resulting in twelve separate operating conditions. Mean data accumulated by means of static and total pressure probe instrumentation are presented at two axial stations: seven jet nozzle diameters upstream and 15 jet nozzle diameters downstream from where the centerline of the nozzle intersects the wind tunnel wall. For one condition at each freestream Mach number, the jet air was seeded with a hydrocarbon trace gas and the flow was sampled at the downstream measurement plane to quantify the mean mixing of the two streams. Surface oil flow visualization was also used to investigate the flow interaction. All results are for air-to-air mixing. The measurements indicate the presence of two pairs contra-rotating vortices. One pair follows the jet trajectory and tends to split the jet into two streams. A smaller pair, rotating in an opposite sense, develops in the near wall region. Reported results include Mach number and volume fraction distributions in the cross plane, as well as jet penetration and mixing efficiency.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-103726 , E-5960 , NAS 1.15:103726 , AIAA PAPER 90-5240 , Second International Aerospace Planes Conference; Oct 29, 1990 - Oct 31, 1990; Orlando, FL; United States
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