EFFECT OF SPLITTER PLATE ON UNSTEADY FLOWS AROUND A BODY OF REVOLUTION AT INCIDENCE

Numerical solutions of the thin-layer approximation of the three-dimensional Navier-Stokes equations have been obtained for flows around an ogive-cylinder body with and without a splitter plate. The numerical results were compared qualitatively with experimental surface pressure, hot-wire anemometer measurements, and smoke visualization of the leeside vortex flow field at high angles of attack. Both experimental and numerical results show that the presence of a splitter plate in the leeward plane of symmetry suppresses the low-frequency, large-scale von Karman vortex shedding from the body and leaves the two primary vortices symmetric and almost parallel to the upper surface of the body. It is suggested that the presence of the splitter plate prevents the interaction between flows on either side of the symmetry plane. As a result of the enforced symmetry (a) the antisymmetric mode of the convective instability near the apex of the body cannot be excited and therefore the vortices remain symmetric, staying low and parallel to the upper body surface; and (b) the antisymmetric mode of the absolute instability mechanism cannot be initiated, which suppresses the alternate shedding of vortices from the cylindrical portion of the body. On the other hand, high-frequency fluctuations of the shear layer (which could be the result of a local instability not subject to symmetry conditions) remain virtually unaffected by the presence of the splitter plate.