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boundary conditions for hydrodynamic instability?
Posted 2011/09/17 2:58 GMT-4 Computational Fluid Dynamics (CFD) Version 4.2 0 Replies
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Hi
Consider a non-compressible fluid column in 2D axisymmetry (laminar flow,moving mesh). A sinusuodial disturbance is excited along the z axis (by a volume force short pulse) F=F1*sin(2*pi*z/a)*(r/a) a is the column radius
The velocities u and w from the laminar physics are plugged into the prescribed boundary velocities of the moving mesh and that works OK with an open boundary at r=a
How can I set the boundary conditions at Z=0 and Z=L so that the model simulates an infinite column without "edge effects" from the boundaries? (L is the column length)
So far the model runs with no-slip walls but the disturbance weakens rapidly near the top and bottom boundaries.
I've tried symmetry and periodic flow with no success. I've tried both the options of zero and maximum of the disturbance at the boundaries.
There is no background flow in the z direction though there is a periodic z flow due to the disturbance.
Thanks
David
Hello David Segal
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