22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-2.9.4

SLENDER FOREBODY AERODYNAMICS AT HIGH ALPHA

K.Petterson & D.I.A.Poll
Cranfield University, UK

Keywords: cfd, forebody, high angle-of-attack, vortex asymmetry

Combat aircraft forebody vortex flow at high angles of attack is complex and non-linear: the stable and symmetric vortices generated by the nose at lower angles can become asymmetric and unstable as alpha is increased. The forces and moments resulting from such asymmetry may be the determining factor for control power and thus it is necessary to be able to predict the high-alpha characteristics of the forebody accurately as early as possible in the design process. CFD should be the ideal evaluation tool, however, this problem has been shown numerous times to be a challenge for computational simulation. Using the NSMB Navier-Stokes Multi-Block code, an attempt is being made to develop an improved, more physically representative, approach to dealing with this type of problem. Results from preliminary computations using tip excrescences and non-symmetrical solutionmethods on a tangent-ogive geometry are presented, together with initial solutions for the Saab JAS-39 Gripen forebody. The next stages in the work and proposed code improvements for tackling high angle-ofattack forebody flows are also briefly discussed.

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