NASA Technical Report


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Modifications to MacCormack's 2-D Navier-Stokes Compression Ramp Code for Application to Flows with Axes of Symmetry and Wall Mass Transfer


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A computer code for solving the two-dimensional compressible Navier-Stokes equations governing the supersonic/hypersonic flow over a compression ramp as developed by MacCormack was extended to apply to axisymmetric flows over cylinder-flare shapes. Two new operators were developed for this extension, one of which was found to produce an upper stability bound on the step size. This bound is proportional to the Prandtl number and inversely proportional to the ratio of thermal capacities of the fluid times the maximum value over all grid points of the kinematic viscosity scaled by the radial coordinate value. Additionally, the computer code was modified to allow for the option of wall mass transfer. This required reformulation of the hyperbolic fine mesh operator because of an assumption in the development of the original operator that the wall-normal velocity in the fine mesh is much less than the sound speed. Numerical results are presented for a particular hollow cylinder-flare configuration, and comparisons are made with the experimental data of Roshko and Thomke and with the results of a boundary-layer code attributable to Patankar and Spalding. (Author).




Inverse Solutions for Laminar Boundary-layer Flows with Separation and Reattachment


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Numerical solutions of the laminar, incompressible boundary-layer equations are presented for flows involving separation and reattachment. Regular solutions are obtained with an inverse approach in which either the displacement thickness or the skin friction is specified; the pressure is deduced from the solution. A vorticity--stream-function formulation of the boundary-layer equations is used to eliminate the unknown pressure. Solutions of the resulting finite-difference equations, in which the flow direction is taken into account, are obtained by several global iteration schemes which are stable and have unconditional diagonal dominance. Results are compared with Klineberg and Steger's separated boundary-layer calculations, and with Briley's solution of the Navier-Stokes equations for a separated region. In addition, an approximate technique is presented in which the streamwise convection of vorticity is set equal to zero in the reversed flow region; such a technique results in a quick forward-marching procedure for separated flows.




NASA SP.


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NASA Technical Note


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Boundary Layer Effects


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In 1975 the U.S. Air Force and the Federal Republic of Germany signed a Data Exchange Agreement numbered AF-75-G-7440 entitled 'Viscous and Interacting Flow Fields.' The purpose was to exchange data in the area of boundary layer research. It includes both experimental and theoretical boundary layer research at speeds from subsonic to hypersonic Mach numbers in the presence of laminar, transitional, and turbulent boundary layers. The main effort in recent years has been on turbulent boundary layers, both attached and separated in the presence of such parameters as pressure gradients, wall temperature, surface roughness, etc. In the United States the research was conducted in various Department of Defense, NASA, aircraft corporations, and various university laboratories. In the Federal Republic of Germany it was carried out within the various DFVLR, industrial, and university research centers.