I have a question.In LU-SGS method, the solution process is the following:

(L+D)Q(i,j) = RHS(i,j)

(U+D)W(i,j) = D(i,j)Q(i,j)

In the above, L = -[A(i-1,j)+B(i,j-1)]

D = [V/DT + R(A) + R(B)]I

U = [A(i+1,j)+B(i,j+1)]

Now overset grid method is used, and point (i-1,j) or (i,j-1) is a fringe point,how to deal with this problem?

Thank you for your reading and Thank you very much for your answer!

Please answer my question !Thanks !