THE ENGINEERING OF MULTIBLOCK MULTIGRID SOFTWARE FOR NAVIER-STOKES FLOWS ON STRUCTURED MESHES

The paper describes EURANUS-a general software software system for the simulation of 3-D Reynolds-averaged Navier-Stokes flows about complex geometries, being developed for the European Space Agency for use as a major tool in its aerothermodynamic design work. The paper emphasize s the software engineering aspects of creating a general multiblock/mu ltigrid solver. A geographically-distributed team of programmers are c onstructing the system with the idea that it should be a highly ordere d and comprehensible platform upon which new formulations and methods can be incorporated in the future by people who did not participate in writing the original code. Presently, the software treats either perf ect gases or air in chemical equilibrium. Closure of the Reynolds stre sses is provided by either the Baldwin-Lomax turbulence model, or the kappa-epsilon model. The key to a successful multiblock code, particul arly if it is to serve as an evolving platform, lies in the design of a suitable data structure and a concept for the management of the data . With such a data structure we have designed a general framework of m odular coding that incorporates various spatial discretization schemes based on either central or upwind differencing and either explicit of implicit time integration. Residual averaging and a multigrid techniq ue accelerate the convergence to steady state. Two computed examples o f viscous laminar hypersonic flow around the HERMES spaceplane provide an initial demonstration of the code.