Boundary condition for wind tunnel (subsonic)

flyingorc · April 17, 2017, 00:57

Hello,

I'm trying to set up a simulation domain for wind tunnel tests comparison. In the model tests, the foil (actually a marine rudder) was installed on the ground (floor). The side walls and ceilings of the tunnel was considered to have litter effect on the flow around the foil.

For the simulation domain, what boundary condition should I use for the ground? I think by right it should be wall (no-slip). Will this require very fine mesh on the whole floor?

I have tried both wall (no-slip) and symmetry for the ground floor, the results were quire similar.

For this case, what will be the actual difference among slip wall, no-slip wall and symmetry conditions for the ground floor. In terms of accuracy and computational cost, which one would you suggest?

Many thanks.

RocketGuy · May 10, 2017, 15:32

Depends on a lot of factors. For example, you say the rudder was installed on the ground. I'm imagining the rudder sticking up vertically. If that's the case, where were the measurements taken on the rudder? I imagine if it was by pressure taps or something like that it would be far enough away from the wall that the BC would have less effect. But if you're interested in comparing the whole flow solution, then yes you would want to have the wall bc.

Are you simulating laminar or turbulent flow? This will have an effect on the wall resolution that you need.

April 17, 2017, 00:57	Boundary condition for wind tunnel (subsonic)	#1
flyingorc New Member Join Date: Jun 2015 Posts: 2 Rep Power: 0	Hello, I'm trying to set up a simulation domain for wind tunnel tests comparison. In the model tests, the foil (actually a marine rudder) was installed on the ground (floor). The side walls and ceilings of the tunnel was considered to have litter effect on the flow around the foil. For the simulation domain, what boundary condition should I use for the ground? I think by right it should be wall (no-slip). Will this require very fine mesh on the whole floor? I have tried both wall (no-slip) and symmetry for the ground floor, the results were quire similar. For this case, what will be the actual difference among slip wall, no-slip wall and symmetry conditions for the ground floor. In terms of accuracy and computational cost, which one would you suggest? Many thanks.

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May 10, 2017, 15:32		#2
RocketGuy New Member Jory Join Date: Apr 2017 Location: Canada Posts: 4 Rep Power: 8	Depends on a lot of factors. For example, you say the rudder was installed on the ground. I'm imagining the rudder sticking up vertically. If that's the case, where were the measurements taken on the rudder? I imagine if it was by pressure taps or something like that it would be far enough away from the wall that the BC would have less effect. But if you're interested in comparing the whole flow solution, then yes you would want to have the wall bc. Are you simulating laminar or turbulent flow? This will have an effect on the wall resolution that you need.