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Dynamic Ground Effect Simulations

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Old   March 16, 2020, 06:16
Default Dynamic Ground Effect Simulations
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James Permain
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I am hoping someone can help me with a possible way I may be able to define the position of my ground wall boundary relative to my 2D moving airfoil for which I want to simulate dynamic ground effect.

I am going to be running dynamic simulations for a NACA4412 airfoil under the influence of ground effect. I will be moving my airfoil in two ways during my simulations:

1) A constant pitch angle and constant sink rate approach to the ground
2) A varying pitch angle rotation at a given height above the ground

I need to define my airfoil's instantaneous height above the ground as the distance between the ground and its closest point to the ground. For angles above roughly 1 degree this is always the trailing edge, but for lower pitch angles this point of closest approach varies with pitch.

I therefore need a way to extract the minimum distance from my airfoil's geometry to the ground wall so that I can match values of lift and pitching moment to given heights.

If there was also a way to create a field function that I could plot/export that would be great, and if I could also use the field function as an input into the origin of my background (and thus wall boundary) I would be able to manually define heights for these tricky pitch angles based off the airfoil's geometry.

Any ideas on how I can do this are much appreciated! Please ask for any clarification if this post is not clear; it is my first one on this forum!
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Old   March 19, 2020, 14:17
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Is this a transient simulation? If so you can easily define a coordinate system at the non-moving component and then evaluate the minimum of position (using a report) on the airfoil boundary. Recording that as a monitor will give you a plot of time vs height.
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Old   March 20, 2020, 09:31
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I would also make the ground boundary a symmetry plane so it doesnt grow a boundary layer but does act like the ground.
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Old   March 21, 2020, 08:00
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Quote:
Originally Posted by me3840 View Post
Is this a transient simulation? If so you can easily define a coordinate system at the non-moving component and then evaluate the minimum of position (using a report) on the airfoil boundary. Recording that as a monitor will give you a plot of time vs height.
Yes these are transient simulations. This is exactly what I was looking for. I have implemented this and it's working just right. Thank you for your help.
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Old   March 21, 2020, 08:02
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Thank you for your suggestion Chris. I have set the wall boundary to a slip condition under the shear stress condition so this should prevent the formation of a boundary layer anyway.
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