SEAGULL was originally developed to model internal and external inviscid, perfect-gas supersonic flow fields. Utilizing a floating shockfitting technique, it gives a quick and accurate evaluation of flow field geometries to determine first-order supersonic inlet and nozzle performance.
The original version of this program was incorporated into the program SRGULL (LEW-15093) for use on the National Aero-Space Plane project, its duty being to model the forebody, inlet and nozzle portions of the vehicle. However, the real-gas chemistry effects in hypersonic flow fields limited the accuracy of that version, because it assumed perfect-gas properties. Particularly, the nozzle calculations were constrained as the program was unable to account for flow property variations due to the presence of hydrogen combustion products.
As a result, SEAGULL has been modified to include a real-gas equilibrium chemistry methodology. The governing equations have been modified to incorporate real-gas equilibrium variations of specific heat and molecular weight in the flow field. Also, new shock and expansion routines have been incorporated to account for the gas property changes encountered. Finally, a chemistry routine has been added to provide air properties as well as account for hydrogen combustion products. This modified version of SEAGULL maintains as much of the original program as possible, and it retains the ability to execute the original perfect-gas version.
SEAGULL carries the NASA case number LEW-15326. It was originally released as part of the NASA COSMIC collection.