Section 10 Feb 2009

For pipe, what boundary condition we are using?
Wall
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Inlet Outlet

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Wall

Compared to pipe which is internal flow, flow past cylinder is a external flow.

For boundary condition, we are imposing free stream condition. Determine how far we need to go.

If we go far enough from cylinder, we will impose zero gradient (not really right). We want to set it such that the boundary conditions will not affect the flow near cylinder.

We have a cylinder, outer boundary is going to look like this.

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10R 40R

Experience tell that the distance from cylinder is shown above. We dont want to create too big of the model to waste unnecessary computing power.

Only use fine mesh in region of interest and region where activity is a lot.

Region around cylinder and also at the wake.

Not much action happen on the front part. That's why we use grading on the front part.