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-   -   The Boundary Condition about the Flat Plate (http://www.cfd-online.com/Forums/main/4262-boundary-condition-about-flat-plate.html)

boing January 4, 2002 19:22

The Boundary Condition about the Flat Plate
 
Hello, everone, I am trying to verifying my own code, I want to compute the laminar flow arond the flat plate , please give me some suggestions on the boundary treatment:

---------------------------------

| |

| |

| |

------- +++++++++++++++++++++++++

^ J

|

--> I

I = Imin : inflow boundary condition (Riemann Invar.) I = Imax : outflow boundary condition (Riemann Invar.) J = Jmin : (symmeteric boundary condition and non-slip

boundary condition) J = Jmax : farfield boundary condition

I used the boundary condition defined above, but I could not get the correct solution ?!


frank January 6, 2002 17:53

Re: The Boundary Condition about the Flat Plate
 
Setting far field conditions at the upper boundary is wrong, if you set the v-velocity to zero. If you look at the blasius-solution you will immediately see, that the v-velocity does not approach zero but a constant value. So, you should treat the upper boundary (JMAX) as outflow. At IMAX using riemann invariants is not great either, since the entropy is not constant in the boundary layer. That might lead to big problems. I use a prescribed pressure and extrapolate the velocity and density. From that one can get the energy for the energy equation. The left border should be placed sufficiently away from the leading edge of the plate. I have a plate of length 2 and the left border about 0.5 or 1 from he leadin ede away.



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