I’m trying to calculate drag at low ambient pressure, but getting errors in the pressures.
This is a simplification of my Hyperloop project, to find the drag of a pod at high speed and vacuum.
Hyperloop runs up to 250 m/s in a tube lower than 1kPa absolute pressure. So I guess the simulation must be compressible, I was getting good flow pictures, but absurd drag figures.
In the test disc project, I have checked the pressure and drag force on a simple disc. At atmospheric pressure, compressible and incompressible gave similar results. But at 1 kPa absolute, the compressible drag only reduced by half, while the incompressible reduced by 100X, as expected. In each case the drag force from results was consistent with the pressures shown in the coloured image. So the pressures in the compressible simulation are way out.
I’ve been to find the best compressible model. The default settings failed (too many iterations) with any speed. So I’ve copied all the parameters from Ali’s Airliner project, and managed to get up to 30 m/s. But I would like 200 m/s if possible.
Thanks for your help