Confusion between 'nonslip' and 'slip' B.C
For nonslip B.C, the velocities u and v are set zero. For slip B.C, the velocity u(assumed as the normal velocity) is only set zero. Is the solid wall in physics modeled by which one? Ideally, the fluid flow does not penetrate the wall and the tangential velocity may not be disappeared. In these cases, we can say that the wall is a slipboundary condition. I would like to ask you all about the distintion between the use of 'nonslip B.C and 'slip B.C'. The objective of this equation is to find out the way to implement the solid wall in 2D compressible flow simulations. Thanks in advance!

Re: Confusion between 'nonslip' and 'slip' B.C
> For slip B.C, the velocity u(assumed as the normal velocity) is only set zero.
wrong, this is nonpenetrating bc which is applied for every rigid walls. Normal component of velocity on wall is zero, U.n = 0 but for slip/noslip bc, we work on tangential component of velocity vector, for no slip we have zero tangential volocity and for slip bc we have zero derivative of tangential velocity. If you work with a coarse mesh, so your boundary layer (near wall) is not resolved due to coarse mesh, slip bc is more feasible. 
Re: Confusion between 'nonslip' and 'slip' B.C
If so, when are you using the nonslip B.C to impose the solid wall? Is there any case where the no slip B.C is properly applied?

Re: Confusion between 'nonslip' and 'slip' B.C
Noslip is applied to solid boundaries in viscous flow. It actually imposes a continuity of velocity at the boundary. If the boundary is moving then fluid particles at the surface take on the velocity of the surface. If the surface is not moving then the fluid velocity at the surface is zero.

Re: Confusion between 'nonslip' and 'slip' B.C
I am solving compressible inviscid flows. Is it applicable to my cases as well?

Re: Confusion between 'nonslip' and 'slip' B.C
If you are solving the inviscid (Euler) equations then the slip wall condition is the appropriate condition to apply.

Re: Confusion between 'nonslip' and 'slip' B.C
Thanks ag!

Re: Confusion between 'nonslip' and 'slip' B.C
Actually for an inviscid fluid the only boundary condition you should be applying is no flow normal to the surface. The noslip condition arises in a viscous fluid because the equations are higherorder and so need additional boundary conditions.

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