Using "opening" to simulate plane flying through air

tyw7 · February 18, 2019, 17:56

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.

February 18, 2019, 17:56	Using "opening" to simulate plane flying through air	#1
tyw7 Member Thu Win Join Date: Apr 2017 Posts: 70 Rep Power: 9	Can I use an "opening" to simulate a condition where the plane is flying through the air?

February 18, 2019, 18:32		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	It depends. A vague question gets a vague answer. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 18, 2019, 18:40		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	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. aero_head likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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February 18, 2019, 18:33		#3
tyw7 Member Thu Win Join Date: Apr 2017 Posts: 70 Rep Power: 9	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?