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Public Domain Aeronautical Software (PDAS)  

This package was developed to compute the inviscid super/hypersonic flow field about complex vehicle geometries accurately and efficiently. A second-order accurate finite difference scheme is used to integrate the three-dimensional Euler equations in regions of continuous flow, while all shock waves are computed as discontinuities via the Rankine-Hugoniot jump conditions. This package has the ability to compute blunt nose entropy layers in detail. Real gas effects for equilibrium air are included using curve fits of Mollier charts. This package can be a very useful tool in the design and analysis of high speed vehicles such as supersonic aircraft, hypersonic transports, and re-entry spacecraft (shuttle orbiter).

This package consists of three separate computer programs. STEIN is the program that solves the Euler equations for the flow field. This solution is obtained by following these basic guidelines:

  1. An accurate second order finite difference marching technique is used to numerically integrate the governing partial differential equations;
  2. Shock waves in the flow field are followed and the Rankine-Hugoniot conditions are satisfied across them;
  3. The intersection of two shocks of the same family is computed explicitly;
  4. Conformal mappings are used to develop a computational grid;
  5. Body boundary conditions are satisfied by recasting the equations according to the concept of characteristics;
  6. The edge of the entropy layer on blunt nose vehicles is followed from its origin and the derivatives across the layer formed;
  7. Real gas effects are included when appropriate, by using fits of Mollier charts; and
  8. Sharp leading edge wings are computed using a local two-dimensional solution.

The only limitation to this solution technique is that the Mach number in the marching direction (nose to tail) must be supersonic at every point in the flow field. The region around the nose of blunt nosed vehicles must be computed by another technique (see description of BLUNT below) and once the flow becomes supersonic STEIN can proceed with its calculations. This program has been used extensively to compute external flow fields and has been found to yield accurate results for a wide variety of vehicle configurations flying at Mach numbers between 2 and 26 and having angles of attack to plus/minus 30 degrees.

The program BLUNT is used to find flow fields about blunt nosed portions of the vehicle. BLUNT uses a time dependent computational technique to asymptote to a steady transonic solution. Output from this program can be used by STEIN to define the flow field points where supersonic flow begins. The program QUICK provides the user with a geometry system to model a complex vehicle geometry in a quick, straight-forward fashion. QUICK consists of an initial defining and logical checkout group of routines, which actually set up the mathematical model, and a second group of routines which are used to interrogate the model for cross sectional information. QUICK supplies all geometrical information about the vehicle to STEIN. (Grumman Aerospace Corp. for NASA Langley)

This program was released by NASA through COSMIC as LAR-11891. The italicized text above is from the official NASA release.

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Public Domain Aeronautical Software (PDAS)