[nickna]

Dear all,
The boundary condition for inviscid flow simulation puzzles me. How to set the BC for the tangential velocity? Can I let it be equal to the tangential of the velocity at the adjacent grid in the fluid part? Any help will be greatly appreciated.

[Numsgil]

In an inviscid flow, there's nothing to slow the fluid down tangential to a surface (it's basically frictionless), so the boundary layer can't form, and the fluid next to the boundary can have any relative tangential flow.

So you only need to enforce the no-through boundary condition, and you can let the tangental component remain unconstrained.