The blind-test activity of the GOAHEAD project

This paper describes the blind-test CFD activity of the EU 6th Framework project GOAHEAD. This blind-test activity has been used to evaluate and assess the helicopter CFD codes which are today in use in Europe and to scrutinize the wind-tunnel test conditions with respect to the expected flow phenomena prior to the wind-tunnel test campaign. Results are presented for an isolated fuselage test case, a low-speed (pitch-up) test case, a cruise test case, a high-speed tail-shake test case and a highly-load rotor (dynamic-stall) test case

The Influence of Modelling in Predictions of Vortex Interactions About a Generic Missile Airframe: RANS

Within the framework of the NATO Science and Technology Organization Applied Vehicle Technology Task Group AVT316 calculations have been made of the supersonic flow around a slender body with wings and fins. In this paper a synthesis of the results obtained using the Reynolds Averaged Navier-Stokes equations are presented. The results show significant sensitivity to the choice of turbulence model. Whilst the gross features of the flow are similar, details of the development of the leeward wake are different. Simple linear eddy viscosity models predict vortices that rapidly decay, resulting in weak interactions with the downstream fins and relatively small rolling moments. This is attributed to an over production in turbulence quantities that results in excessive effective turbulent viscosity. Interventions that limit the production of turbulence, for example the SST limiter or curvature corrections, results in vortices that grow more slowly, changing the nature of the downstream interactions resulting in increased rolling moment. The use of more complex formulations, such as Reynolds stress models, that are inherently more capable for highly strained flows, further limits the rate of growth of the vortex cores leading to rolling moment predictions that are 2-3 times greater than those obtained with the simplest models