Computation of Flow around Spheroid at Small Incidence and Study on Vorticity Field

Abstract

In the present study, Navier-Stokes equation is numerically solved by use of a finite difference method to obtain the 3-dimensional flow field around a prolate spheroid at small incidence. The computed flow field shows the same characteristics to that of the observation by a flow visualization technique which was reported in the author's previous report. The existence of a bubble-type separation at the rear end and the nodal point in the surface shear-stress pattern are recognised in the computed results.The 3-dimensional vorticity field is derived from the result of the computation. The vorticity structure is analysed by dissolving the vorticity vector into two components, i. e. the one is the component along the flow direction (locally streamwise vorticity) and the other component is in the locally transverse plane. The two components of the vorticity show different characteristics, i. e. the locally transverse vorticity vector shows a maximum value near the fore end and decreases in the downstream as the boundary layer grows. On the other hand, the streamwise vorticity grows in the after region and keeps its value in the wake region, although the magnitude of the streamwise vorticity is quite small compare to that of the transverse vorticity.