SimScale CAE Forum

Boundary conditions, external flow


#1

Hello everyone
Im new to CFD in general, and unsure about the right boundary conditions for external flow .
Im trying to simulate a bullet, but what should the right BC be for top/bottom and sides of the domain?

Would symmetry or free-stream BC be the way to do it?

Hope anyone has a good answer

/Frederik


#2

Hey @Frederik2308

You can try moving wall for the ground (same velocity and same direction as the bullet) and symmetry or slip walls for top/sides.

/Ric


#3

Thanks Ric
How come free-stream isnt the right configuration?
To my knowledge SolidWorks flow uses free-stream as BC in external studies

/Frederik


#4

It should also work :stuck_out_tongue_winking_eye: . Freestream BC for velocity works more or less like inlet-outlet. For each boundary cell, velocity will either be fixed value (if the vector points into the domain) or zerogradient (if it points out).