Use absolute coordinate system when using "translate" on a body?

sciamwow · October 24, 2019, 20:03

Hello!

I am new to Star-CCM+ and am having some issues.

I am running 2D simulations of race car airfoils in ground effect. I am trying to create a macro that will run an angle of attack sweep for the airfoil while keeping the lowest point of the airfoil at exactly 2 inches above the ground. I recognize that this is an important distinction because I have seen other threads that want to perform the same task without ground effect could simply adjust the angle of the incoming flow rather than the airfoil itself.

I have been doing this manually by finding the minimum height value of the airfoil, translating it down by that amount, then translating it up 2 inches and re-meshing. I recorded a macro that adjusts the angle and re-meshes just fine, but I can't find a way to make the macro translate the airfoil down by a variable distance, namely the lowest point of the airfoil from the ground, before moving it back up two inches. It would be super simple if I could move the body to a specific point using absolute coordinates, but I don't see a way of doing so.

If anybody has any insight (or a different way of approaching this), please let me know!

Thanks in advance.

cwl · October 25, 2019, 06:13

Well, it can be done like this:
- set the Minimum Report for $$Position[2] (z-coordinate) at Airfoil surfaces;
- move/rotate/etc the airfoil;
- mesh incorrectly positioned airfoil, this will allow to get the required translation via Minimum Report;
- translate according to Minimum Report and 2 inches.
Not the best way, but at least it should work.

October 24, 2019, 20:03	Use absolute coordinate system when using "translate" on a body?	#1
sciamwow New Member Robert Sciambra Join Date: Oct 2019 Posts: 1 Rep Power: 0	Hello! I am new to Star-CCM+ and am having some issues. I am running 2D simulations of race car airfoils in ground effect. I am trying to create a macro that will run an angle of attack sweep for the airfoil while keeping the lowest point of the airfoil at exactly 2 inches above the ground. I recognize that this is an important distinction because I have seen other threads that want to perform the same task without ground effect could simply adjust the angle of the incoming flow rather than the airfoil itself. I have been doing this manually by finding the minimum height value of the airfoil, translating it down by that amount, then translating it up 2 inches and re-meshing. I recorded a macro that adjusts the angle and re-meshes just fine, but I can't find a way to make the macro translate the airfoil down by a variable distance, namely the lowest point of the airfoil from the ground, before moving it back up two inches. It would be super simple if I could move the body to a specific point using absolute coordinates, but I don't see a way of doing so. If anybody has any insight (or a different way of approaching this), please let me know! Thanks in advance. Last edited by sciamwow; October 24, 2019 at 20:05. Reason: Added information.

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October 25, 2019, 06:13		#2
cwl Senior Member Chaotic Water Join Date: Jul 2012 Location: Elgrin Fau Posts: 438 Rep Power: 18	Well, it can be done like this: - set the Minimum Report for $$Position[2] (z-coordinate) at Airfoil surfaces; - move/rotate/etc the airfoil; - mesh incorrectly positioned airfoil, this will allow to get the required translation via Minimum Report; - translate according to Minimum Report and 2 inches. Not the best way, but at least it should work.