Hello everyone. I'm new to this forum and very impressed so far. I'm making a program which simulates the flight of an object. In order to do that, I have to compute the coefficient of drag. This is the first problem. From what I know, it should be possible to determine this number (at least approximately) by examining a 3d model of the object. Second: I'm looking for the function which describes how the coefficient of drag changes with the Mach and the Reynolds number (Cd[Ma,Re]). I have seen it has been done (http://home.snafu.de/l.moeller/Ballistik/Airdrag.html), but I wasn't able to extract the formulas from the source code. Has anyone got a suggestion to these questions? Thank you in advance.