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Bifurcation approximation for binary and thermal diffusion coefficients, mixture viscosity, and thermal conductivity of laminar boundary layer
Nongray radiation transport model for use in ablator-contaminated boundary layers
Nonsimilar solution of incompressible turbulent boundary layer by integral matrix method
Theoretical predictions of turbulent boundary layer development under the influence of strong favorable pressure gradients made using a finite-difference calculation procedure are compared to experimental data. Comparisons are presented for low speed flows with and without wall heat transfer as well as for supersonic flows with adiabatic walls. The turbulence model used is governed by an integral form of the turbulence kinetic energy equation and the results are compared with predictions made using a conventional equilibrium turbulence model based upon Prandtl's mixing length, a Clauser-type eddy viscosity model used by Cebecci and Mosinskis, and a two-equation turbulence energy model of Launder and Jones.
Methods of predicting integral parameters and skin-friction coefficients of turbulent boundary layers developing over moving-ground-planes are evaluated using test information from three different wind tunnel facilities at the NASA Langley Research Center. These data include test information from the VSTOL tunnel which is presented for the first time. The three methods evaluated were: (1) relative integral parameter method, (2) relative power law method, and (3) modified law of the wall method. Methods (1) and (2) can be used to predict moving-ground-plane shape factors with an expected accuracy of + or - 10%. They may also be used to predict moving-ground-plane displacement and momentum thicknesses with lower expected accuracy. This decrease in accuracy can be traced to the failure of approximations upon which these methods are based to prove universal when compared with VSTOL tunnel test results.
Methods of predicting integral parameters and skin friction coefficients of turbulent boundary layers developing over moving ground planes were evaluated. The three methods evaluated were: relative integral parameter method; relative power law method; and modified law of the wall method.
The details of extended physical processes, such as the gas dynamic flow over an airfoil, the reactive flow through a combustor, or the electric field in a multi-contact transistor, are understood by solving the differential equations of a mathematical model of the process. The accuracy of finite difference methods for the numerical solution of the equations is increased if the underlying mesh fits the region boundaries and is closely spaced in regions where the solution is rapidly varying. Automatic methods for producing a satisfactorily adjusted mesh were developed for one dimensional problems. In one simple, effective scheme of this kind the unknown function and the distribution of mesh modes are found simultaneously, the nodes being placed so that they correspond to points uniformly spaced on the solution curve. In a two dimensional generalization, the nodes correspond to points equally spaced on the solution surface in two directions that are as nearly orthogonal as possible. Examples of such meshes are shown.
A cooled porous region has a plane surface exposed to a specified spatially varying heat flux. The coolant leaves the region through this surface, and it is desired to control the flow distribution to maintain a specified uniform surface temperature. This is accomplished by having the coolant entrance surface shaped to provide in the region the necessary variation of path length and, hence, flow resistance. The surface shape at the coolant entrance is found by solving a Cauchy boundary value problem. An exact solution is obtained that will deal with a wide variety of heating distributions for both two- and three-dimensional shapes.
The formulation of the planetary boundary layer (PBL) and stratocumulus parametrizations in the UCLA general circulation model (GCM) are briefly summarized, and extensive new results are presented illustrating some aspects of the simulated seasonal changes of the global distributions of PBL depth, stratocumulus cloudiness, cloud-top entrainment instability, the cumulus mass flux, and related fields. Results from three experiments designed to reveal the sensitivity of the GCM results to aspects of the PBL and stratocumulus parametrizations are presented. The GCM results show that the layer cloud instability appears to limit the extent of the marine subtropical stratocumulus regimes, and that instability frequently occurs in association with cumulus convection over land. Cumulus convection acts as a very significant sink of PBL mass throughout the tropics and over the midlatitude continents in winter.
A one-component laser Doppler velocimeter (LDV) has been used to measure the two-dimensional, periodic flow field about a double circular arc, compressor blade in cascade. Eleven boundary layer profiles were taken on both the pressure and suction surfaces of the blade, and two were taken in the near wake. In this part of the study, the LDV system is described and the suction surface flow field is documented. The suction surface profiles appear to separate both at the leading edge and again somewhat beyond midchord; the leading edge separation apparently reattaches by 2.6 percent chord.
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Progress was made on further flow visualization of vortex-leading edge interaction, in conjunction with characterization of the unsteady pressure field. The range of scale of an elliptical leading edge, relative to the incident primary vortex, was determined. The scale of the incident vortex was characterized in terms of mean shear layer parameters. An overview of the interaction mechanism for the range of thin to thick leading-edges is given. The interaction mechanism corresponding to the case where the incident vortex is above the leading-edge is given for hydrogen bubble wires well upstream of and at the tip of the leading edge. A sample of the instantaneous pressure distribution for the case where the incident vortex dives beneath the edge is presented. The effect of scale of the incident vortex relative to that of the leading-edge was examined. The circulation and length scale of the incident vortices in the street are being characterized.
The design of laminar flow fuselages and advanced swept wings at high-subsonic compressible speeds can benefit from a correlation of compressible transition experiments with the e exp n transition-prediction method. A computational analysis has been conducted to investigate the detailed transition measurements obtained by Boltz et al. (1956, 1960) for two bodies-of-revolution. Nonadiabatic wall conditions were included in the analysis when wall-temperature measurements were available.
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