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Particles do not hit the wall

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Old   April 15, 2010, 08:21
Default Particles do not hit the wall
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Cedric Van Holsbeke
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I am doing simulations with lagrangian particles (kinematicCloud), but I am having unrealistic results close to the wall. When particles hit the wall, they should stick to it, as defined in my kinematicCloudProperties file:

Code:
StandardWallInteractionCoeffs
{
    type        stick;
}
In StandardWallInteraction.C, in the correct(...) function it is found that this means:
  • Particle is kept in the system
  • U is set to 0 ( U = vector::zero; )
This function is called by the hitPatch(...) function in KinematicParcel.C. However, it seems that this function is never called!

I am using particles with a diameter of 9e-6 which is smaller as my grid size. Instead of hitting the wall, the particles float above it with a distance in the order of 4e-6 6e-6. This distance is about (but not exactly!) the same as the half of the particle diameter, so it can be that they touch, and that this distance is the distance from wall to particle centre.

However, the U becomes small (1e-3 ... 1e-7), but not completely 0 so there is still a slight movement of the particles. This means that the U = vector::zero is not called.

I have tried it in several simulations, even simulations without flow and only gravity working on the particles. The particles fell down to the bottom, but they still moved a bit in the horizontal direction.

Has somebody else seen this strange behaviour?
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