Hello,

I'm trying to implement ghost points in my computation. These ghost points are reflected along a solid boundary from a fluid point that's near the boundary. Hence, the ghost point are actually inside the solid body. if the fluid point has velocity v(f) (vector) and pressure p(f) (scalar), what is the ghost point's respective values v(g) and p(g)?

The solid boundary is also moving at velocity v(s).

Is this the correct formulation?

p(g)=p(f)

v(g)=v(f)-2(v(f).n)n+2(v(s).n)n

where all are vectors and n=unit vector perpendicular to the boundary . refers to dot product.

I have also attached a picture to explain. Are the ghost vectors correctly drawn?

http://usera.imagecave.com/quarkz/reflection.jpg

Thanks

On the other hand,

another paper uses

u(g)=2*u(s)-u(f) and v(g)=2*v(s)-v(f)

where u and v and the scalar components of the velocity.

This eqn and the above each gives a different answer. So which is correct?