# Few questions..

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January 6, 2018, 17:35
Few questions..
#1
New Member

Fox
Join Date: Jan 2018
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I am doing a science project on determining which type of grid fin is ideal for a rocket landing (Grid Fin is a control device similar to a planar fin but is better).

In this case, I would like to know if CFD has the capability to tell me the total force on the grid fin due to the air stream and if it can tell me the total moment of the grid fin due to the air stream.

Thanks
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 January 7, 2018, 07:47 #2 Senior Member   Join Date: Dec 2017 Posts: 153 Rep Power: 8 Hi, Sure!!!

January 7, 2018, 10:43
#3
New Member

Fox
Join Date: Jan 2018
Posts: 2
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Quote:
 Originally Posted by AliE Hi, Sure!!!
Perhaps I should have specified. My bad.

I know the wall calculator can calculate torque/force but the problem is, is that I don't know what to select on the model to calculate it.

If I wanted to find the total force on the grid fin itself, do I select the underside and topside of the grid fin only? https://imgur.com/a/xUMOh

What should I select when I want to find the torque on the grid fin? The fin obviously, but do I select the hinge and rocket body? https://imgur.com/a/43HH9

 February 2, 2018, 05:15 #4 New Member   Jon Wilde Join Date: Dec 2016 Posts: 25 Rep Power: 9 Just select the surfaces that you need to include. We cannot really answer which ones for you, that is for you to decide But yes, just use the wall calculator. Be mindful of the mesh quality in models like this...

 September 14, 2020, 22:40 #5 New Member   Mike Stroup Join Date: Sep 2011 Posts: 13 Rep Power: 14 Select all the surfaces in the wall calculator dialogue window and remove the surfaces of the domain.

 September 24, 2020, 08:47 #6 New Member   Apolo Join Date: Jul 2009 Posts: 17 Rep Power: 16 One other method would be to use Groups. Grab different segments of surfaces in the setup side, right-click and Add to Group. If done prior to running the model, when you go to the Wall Calculator you can just select the group of interest. That way if you need to run different conditions you don't have to go through the hassle of selecting all the critical surfaces each time. Mithrandir likes this.