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Question on moving mesh, mesh velocity is really small!

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Old   December 14, 2012, 12:15
Default Question on moving mesh, mesh velocity is really small!
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Hi guys,

I am coding a finite volume code to calculate the unsteady pressure for a moving airfoil. I used Roe scheme, and I am really confused with the moving mesh method.

I calculate the mesh moving velocity and it is really small (V_g=1m/s), and the flow velocity V is larger than 200m/s. And it seems that the mesh moving velocity has no influence on the solution.

As I understand, for Roe scheme, the cell surface flux for moving mesh is nearly the same as for stationary mesh, the only different is that the velocity V in eigenvalue for moving mesh is replaced by V_r. (V_r=V-V_g) . However, since V_g is very small, it seems that it has limited influence on the solution.

Can you guys who had the experience in moving mesh help me? Thanks!
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Old   April 27, 2014, 12:03
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Not only eigenvalues but flux vector changes, too. Considering 3D flux in normal direction:

F_0 = \rho (u_n - u_b) \\

F_1 = \rho (u_n - u_b) u + p n_x \\

F_2 = \rho (u_n - u_b) v + p n_y \\

F_3 = \rho (u_n - u_b) w + p n_z \\

F_4 = (u_n - u_b) E + p u_n \\
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Old   April 28, 2014, 13:37
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from a physics stand point, it makes sense that if the boundary moves slowly relative to the flow velocity it will be insignificant ( unless there's some special case). This is true until the geometry changes enough to impact the flow.
It might be considered quasi-static.
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