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发表于 2011-7-25 17:03:46
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来自 江苏扬州
12# bianzhou12
Impedance是无限域的意思,不反射应力波;
Rigid是固定壁,比如河塘的底面;
Flow out表示材料可以流出去。
The values of the boundary conditions that can be set for each face are:
Flow Out
Use the Flow Out boundary condition to flow out material through cell faces. The boundary condition makes the material state of the dummy cell outside the Euler domain the same as that of the cell adjacent to the Flow Out boundary, thus setting the gradients of velocity and stress to zero over the boundary. This approach simulates a far field solution at the boundary, but is only exact for outflow velocities higher than the speed of sound and is an approximation for lower velocities. Therefore, the Flow Out boundary condition is approximate in many cases, and should be placed as far as possible from region of interest and best at a location where the gradients are small.
Impedance
Use the Impedance boundary condition to transmit waves through cell faces without reflection. The boundary condition predicts the pressure P in the dummy cell outside the Euler domain from the impedance, particle velocity, and the pressure of the cell adjacent to the Impedance boundary. Only the perpendicular component of the wave is transmitted without reflection. Therefore, the Impedance boundary condition is only approximate, and should be placed as far as possible from region of interest.
Rigid
Use the Rigid boundary condition to prevent flow of material through cell faces. The cell faces are closed for material transport and act as rigid non-slip walls. The Rigid boundary condition takes the material state of the dummy cell outside the Euler domain as a mirrored image of the cell adjacent to the Wall boundary, thus setting the normal material velocity at the rigid wall to zero and leaving the tangential velocity unaffected. |
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