Abstract: The laminar flows around a 4∶1 prolate spheroid and other ellipsoids with different axes ratios are simulated by using pseudo compressibility method to solve the incompressible N S equations. Both a conventional second order central differencing scheme and a third order upwind compact differencing scheme are used to approximate to the inviscid terms. From the computed skin friction lines, off surface streamlines and cross section streamlines, patterns of the 3D separation and the resulting vortices are analyzed for 10° ≤ α ≤70°. The aerodynamic characteristics are also computed against axes ratios. The results shows that the flow remains symmetric at α≤ 40° but will become asymmetric and unsteady at α=70°. The computed flow patterns agree with experiments qualitatively. The thinner the ellipsoid is, the more upstream the open separation will occur.The narrower the cross section is , the smaller the separated region will be. Because the shape of the cross section has influence on the size of separation and the strength of vortices, this study may provide background for improving the aerodynamic characteristics in the design of aircraft fuselages.

Key words: ellip soids, NavierStokes equations, numerical analysis, separated flow