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Major Enhancements in GASP v4

GASP Version 4, due out in the second half of 1999, will offer several enhancements over GASP v3. The four main enhancements are:

1) numerous improvements to the graphical user interface (GUI),
2) a more accurate, robust, and effi- cient time-accurate capability,
3) automated treatment of chimera overlapping grid systems, and
4) a more sophisticated and complete parallel implementation.

There are three areas of major change to the GASP GUI:

1) the zonal boundary window has been re-designed,
2) the print utility has been incorporated into the GASP GUI, and
3) windows used for setting up the execution of GASP have been added.

Because the zonal boundary implementation in Version 4 has been completely revised to include automated hole cutting and zonal boundary interpolation, the zonal boundary window has also had a complete overhaul. The main function of the zonal boundary window is now to set up the very minimal input for the automated routines and to view the results (holes, point-to-point mappings, and interpolation stencils).

Since Version 3.2, the GASP GUI has included some graphical visualization. In Version 4, AeroSoft has built a capability on top of the visualization that allows the user to output flow quantities based on the graphical objects. In previous versions of the software, the user relied on a separate PRINT utility to output a set of variables at given locations (i.e., (i,j,k) ranges) and formats (e.g., Plot3D, line output, etc.). Now the data associated with one or more graphical objects (i.e., the (i,j,k) ranges) is utilized in conjunction with a variable list and output format to produce results similar to PRINT directly from the GASP GUI.

As stated earlier, one of the main changes to GASP was the addition of a more sophisticated and complete parallel implementation. An important aspect of that implementation is making it simple for the user to run parallel problems on a wide range of platforms. As a result, a new set of windows for controlling the execution of GASP has been created. The new windows include some of the information from the block and sweep windows in Version 3, but the information is presented in a new, more global perspective, so that the user can have a much better feel for how they are going to run the problem. In addition, new capabilities have been added to aid in setting up and selecting processors, viewing various summaries of the input, selecting graphical residual output and solution file output (particularly for time accurate calculations), and for executing the code directly from the GUI.

Although GASP has always been able to compute time-accurate problems, Version 4 will offer a state-of-the-art time-accurate capability. A dual-time stepping algorithm has been added to allow for higher-order time accuracy in conjunction with the use of implicit time integration schemes which provide more stability at higher time steps. In addition to incorporating a more accurate and robust scheme, AeroSoft has implemented new time-accurate boundary conditions which enable the user to input a time series of flow boundary conditions for any boundary cell or set of cells. The solution file format has also been augmented to contain solution information at various time levels.

In response to the demand to be able to solve very complicated geometries, AeroSoft has added the ability to compute flows on arbitrary (point-to-point, patched, and overlapped) grid systems. With minimal user input (selecting a set of zones and sequences with defined boundary conditions -- a requirement for running the problem anyway), GASP Version 4 will automatically identify and set up point-to-point and patched zonal boundaries, cut holes, and finally compute the interpolation coefficient for all fringe cells (those cells around the boundary of holes and along the edges of boundaries of overlapped grids).

GASPv3 utilizes compiler directives to compute in parallel over a set of zones on shared-memory architectures. Version 4 expands upon this capability by allowing the user to compute on all types of parallel architectures through the use of MPI. In addition to the more general MPI implementation, GASP v4 gives the user a choice of implicit or explicit zonal boundary treatment allowing the user to trade-off speed and parallel performance versus convergence rate. GASP v3 only provides explicit zonal boundaries which can result in slower convergence for problems which are decomposed onto many processors.

The new automated chimera implementation also utilizes MPI to cut holes and compute coefficients in parallel. For steady-state problems, this is not a big issue; however, in future releases, AeroSoft plans to add a moving grid capability in which the hole cutting and coefficient computing steps will have to be repeated several times. Therefore, parallel implementation of these steps will be critical to overall performance.

AeroSoft, Inc.
1872 Pratt Drive, Suite 1275
Blacksburg, VA 24060
(540) 557-1900
Fax (540) 557-1919
Email questions@aerosft.com