Learning Forum

[Ammar Ahmed]

Hey, I hope everyone is doing well. I am conducting transient density based cfd analysis of a spinning projectile at various mach speeds from subsonic to supersonic to validate my cfd analysis with experimental drag results. At most of the speeds, my error in drag results is less than 10% but there are 2 challenges I am facing:

1. Firstly, I am unable to achieve cnvergence at exactly 1 mach speed maybe because it is very critical speed in the transonic region.

2. Secondly, at mach speeds from 3.2 to 7, I am achieving a very good convergence by keeping the time step size 1e-6 but the error with experimental results is from 12% at 3.2 mach speed to 32% at 7 mach speed.

So what do i need to do differently in order to get results at 1 mach speed and reduce the percentage error at high supersonic and hypersonic speeds.

Any help would be appreciated.

 

[Rob]

Look at the contours & flow vectors to understand what's going on plus the monitor output: just looking at residuals and forces won't tell you what's going on in the model.