Accuracy Issues in the Prediction of Supersonic Inlet Flows

Abstract

Numerical and modeling accuracy issues are examined for two types of inlet flow analyses through a discussion of how numerical and modeling errors can influence the predicted inlet performance. For supersonic inlets, two types of procedures are in use at Boeing. The first is a zonal method that has been in use and under development for two decades. The second is based on solution of the Reynolds averaged NS (Navier-Stokes) equations; NS methods have been applied to the prediction of supersonic inlet flows for only about the last five years. The primary advantage of the zonal procedure is that accurate performance predictions are obtained on a computer workstation for only modest computational resources. The primary advantages of the NS procedures are the almost unlimited geometries and flows that can be considered. The accuracy (or lack thereof) achievable by either type of procedure is determined by the errors introduced by both the numerical procedures and by the modeling. At present, NS analysis is at about the same level of accuracy as the more mature zonal procedure. NS analysis offers, however, a wider range of flows and geometries that can be analyzed and less reliance on a sophisticated understanding of inlet flow phenomena necessary for modeling. Continuing advances in computing technology foretell a bright future for the use of CFD (Computational Fluid Dynamics) for supersonic inlet design when accuracy issues that constrain the usefulness are addressed.