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Midterm DEM - Boundary Collisions

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ME964JoshA

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Unread post Tue Apr 12, 2011 9:38 pm

Midterm DEM - Boundary Collisions

Hey Toby,

How do we handle the Vnij and nij vectors in the collisions with the wall? Is the wall just V=0? nij is just the direction normal to the wall? Also how do we calc meff with collsions with a wall?

It seems I am having problems with particles moving past the boundaries. Any suggestions?

Thanks in Advance.
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TobyH

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Unread post Wed Apr 13, 2011 7:37 am

Re: Midterm DEM - Boundary Collisions

Josh,
The same force model is used for collisions with the wall. For the wall, just take V=0 and nij=normal direction to wall, as you guessed. In this case, you can take meff to be the mass of the particle.
My advice is to compute particle-boundary forces in a separate kernel. I suggest one thread per particle, and check each particle against all boundary planes (see lecture slides for computation to determine if a particle is colliding with a plane). If a particle is colliding with a given plane, compute the force and add it directly to the vector of net forces. Note that the variables which hold the plane normals and points are defined and initialized in code I have given you. However, they are only on the CPU, so you will have to either copy them to GPU or pass them as arguments into a kernel.
If you have any other specific questions let me know, but I hope this gets you going.
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ME964JoshA

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Unread post Wed Apr 13, 2011 11:37 am

Re: Midterm DEM - Boundary Collisions

hey can I stop by around 4:00 or after today for some help?
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TobyH

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Unread post Wed Apr 13, 2011 1:07 pm

Re: Midterm DEM - Boundary Collisions

I can be here until about 5:30.

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