Overset Grid CFD Software

Obtaining these codes

OVERFLOW Flow Solver

OVERFLOW is a Navier-Stokes flow solver for structured grids. It can use single block grids or Chimera overset (structured) grid systems. Right-hand side options include central differencing with Jameson 4/2 dissipation and Roe upwinding. Left-hand side options include the Pulliam-Chaussee diagonalized (scalar pentadiagonal) scheme and the LU-SGS scheme. Low-Mach number preconditioning is available for accuracy in computing low-speed steady-state flows.

First-order implicit time advance is used. A time-accurate mode is available, or local timestep scaling can be selected for acceleration to steady state. Grid sequencing and multigrid are also implemented for convergence acceleration.

Performance on the NAS Cray C-90 is 440 MFLOPS per processor; the code runs in a multitask mode with an average concurrency of 6 CPUs for three-dimensional problems. CPU time required is about 8 microseconds/point/iteration.

Memory required is 35 words per grid point of the largest grid block.

FOMOCO Force/Moment Integration Utilities

FOMOCO is a force and moment (and mass and momentum flow) integration package for overset grids. The package handles the removal of overlapped surface grid regions and stitches the resulting surface grids together with rows of triangles (zipper grids). Integration of the desired quantities is then performed on the resultant collection of structured surface grids and zipper grids.

The integration procedure can be executed as a post-processor for the computed solutions, or run as an integral part of the OVERFLOW flow solver, returning a convergence history of the aerodynamic forces.

The author is William M. Chan.


PEGSUS 4.1 Grid Joining Code

The PEGSUS code processes individual component grids, cutting holes and finding interpolation stencils to create an overset grid file and an interpolation file. These are used by the flow solver.

Restrictions: PEGSUS is an Air Force restricted code. As such, one must obtain the original code from the Arnold Engineering Development Center (AEDC). AEDC distributes version 4.0; the NASA "enhancements" are referred to as version 4.1.

To receive the PEGSUS 4.0 software, the Air Force requires that your company be registered with the Defense Logistics Information Services Center as a "certified contractor" to receive export controlled data. To become registered, call 1-800-352-3572 and ask to complete DD form 2345. In the meantime, contact Ms. Bonnie Heikkinen at (931) 454-7885, or heikkinen@hap.arnold.af.mil, and she will fax you the AEDC software release forms. The certification number is required in the box referred to as export control number. After you complete the forms and fax them back to AEDC, it generally takes 1-2 weeks to get Air Force approval.

Once approval for PEGSUS 4.0 has been received from AEDC, the PEGSUS 4.1 Enhancements can be requested from NASA. (One can send both requests in at the same time; I will check with AEDC before releasing the NASA version.)

Note that distribution of the NASA version is restricted to those INDIVIDUALS who have Air Force approval.


Obtaining these codes

These codes are NASA research codes, and are only available within the United States.

Please write a letter (or email) of request for the desired code(s) to the appropriate developer(s) listed below. The letter should include a brief description of the application for which the codes will be used, and a list of those who will have access to the codes.

A completed software usage agreement form will be required as well, and may be available on the web. Once the request letter and agreement form are received and approval granted by NASA, a notification letter is sent to the requestor.

Code transmittal is generally in the form of a mime-encoded e-mail message; note that some of these codes are large. No anonymous FTP site is available; please make arrangements for this transfer.

OVERFLOW and PEGSUS 4.1 (with restrictions)

    Pieter G. Buning
    Configuration Aerodynamics Branch
    Mail Stop 499
    NASA Langley Research Center
    Hampton, VA  23681-2199
Software usage agreements will be sent upon receipt of the request letter.


    William M. Chan
    MCAT, Inc.
    Mail Stop T27B-2
    NASA Ames Research Center
    Moffett Field, CA  94035-1000
A software usage agreement is available online.
URL: http://ad-www.larc.nasa.gov/~buning/codes.html
NASA Official Responsible for Content/Page Curator: Pieter G. Buning < p.g.buning@larc.nasa.gov>
Last Modified: 6 November 2002

Feedback on Langley Products and Services