BCE Marker Guidance

[Dan Fenn]

Hi all,

Is there any documentation available regarding general guidance concerning BCE markers?

I'm setting up a CRM terrain simulation using the test rig demo, but replacing the wheel/tire with my own model. I can generate a triangle contact mesh for the new tire. I see that the test rig code is automatically generating BCE markers based on the contact mesh. Does the density of BCE markers significantly impact the solution accuracy? If so, does changing the triangle density of the mesh affect the density of BCE markers? My wheel has short, thin grousers, and I want to make sure that these are adequately represented by the markers.

Also, the wheel is essentially a hollow cylinder, and I notice that the entire interior portion is being filled with BCE markers. I'm not certain these are necessary, or if they significantly affect performance, but if I'm able to increase performance by removing them, I'd like to do that.

 If there's existing documentation that addresses these questions, I'd appreciate being pointed to it, as I was unable to find it. Otherwise, I appreciate any insight you can give me.

Thanks,

Dan

[Huzaifa Mustafa Unjhawala]

Hello Dan,

The density of the triangles in the contact mesh will not affect the density of the BCE makers since the BCE markers are placed with the same spacing as the fluid domain. To represent short and thin grousers, you would need to reduce the spacing to resolve the features of your mesh. For example, if you had a grouser thickness of 2 cm, you would need to have a spacing of at max 1 cm to get three layers of BCE markers for your grouser. 

That being said, I would highly recommend using a algorithmic approach to generating the markers or using an external tool to go from mesh to markers, because the Chrono function to go from mesh to markers is not the most robust. In this demo you will find an example of an algoirthmic approach to generating the BCE markers - https://github.com/projectchrono/chrono/blob/7e03e3b0ab5d9c1eb6d9f23429102ae474370013/src/demos/fsi/demo_FSI_SlopedSingleWheelTest.cpp#L134
Using something like this ensures that your BCE marker spacing is correct and your wheel shape is accurately captured. You can also make the wheel hollow.

Best

Huzaifa

[Dan Fenn]

Hi Huzaifa,

Excellent--this is very helpful. That source file looks like exactly the kind of thing I'm looking for.

Thanks!

Dan