From 2D to axisymmetric

Nestor

Dear all,

First of all, this is not a post about CFD. I know there are people that can help me out with aerodynamics and that's why I post this here. Some time ago I collaborated with stuff related to Fluent but this is not the case right now.

I have to compute the Cd of an axisymmetric body (exomars module at Mach 20). The hypersonic stuff is no problem, the only thing that changes is the formulation of Cp. I am able to calculate Cd for 2D, but the flow is not 2D. I don't know how to model it for 3D axisymmetric. I thought about revolving my 2D Cd but it really makes no sense. Is there any way of obtaining it from the 2D value? If not, I have plenty of work transforming coordinates to spherical for the front body and modeling a conic forebody as well.

An easy example: is it possible to calculate the sphere drag coefficient from the cylinder value assuming that the back shadowed part (after the top and bottom points) has nule influence at all (as it happens applying Hypersonic Newtonian theory)?