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-   -   Using "opening" to simulate plane flying through air (https://www.cfd-online.com/Forums/cfx/214947-using-opening-simulate-plane-flying-through-air.html)

tyw7 February 18, 2019 17:56

Using "opening" to simulate plane flying through air
 
Can I use an "opening" to simulate a condition where the plane is flying through the air?

ghorrocks February 18, 2019 18:32

It depends.

A vague question gets a vague answer.

tyw7 February 18, 2019 18:33

Depends on?

I am simulating a plane at cruise, so I think the "box" of the wind tunnel could be set as an "opening" with 0 relative pressure. What do you think?

ghorrocks February 18, 2019 18:40

It depends on the Mach number you are simulating, numerical stability considerations, how the boundary is implemented and many others.

The normal way of modelling a body in far field flow (this is the technical term for what you are trying to do) is to put a box around the body with an inlet where the flow goes in and outlet where the flow goes out. Inlet/Outlet pairs tend to be more numerically stable than openings. You need to do sensitivity analyses to find out how close you can put the inlets and outlets to the body - 5 chord lengths upstream for the inlet and 20 chord lengths downstream and to the side would be a good starting point.


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