How to adjust the parameter of "moving patch"

[Daniel Zuo]

Hi,

I'm currently running the "multicore tire testrig" demo with granular terrain to study the tire-soil contact scenario, and I'm having problems trying to modify the 'moving patch' parameters (for example, moving patch generating height, moving patch length) to see how it affects the simulation results. I tried to modify the code in chrono/src/chrono_vehicle/terrain/GranularTerrain.cpp, but it doesn't seem to work. What should I do? 

Thanks！

Regards

[Radu Serban]

Hi Daniel,

 

You do have control over the most important parameters that control the moving patch.  See demo_VEH_GranularTerrain_MovingPatch and the parameters passed to EnableMovingPatch.

A few comments:

• The one parameter that is not exposed to the public API is the height of the lowest layer of moved particles. This is because that is implemented as a factor of the particle radius and its value is constrained by some other considerations (if you really want to play with that, you can change its value from the default 3 to something else in GranularTerrain.cpp at line 64). However, the same effect of increasing this height can be obtained (more robustly) by increasing the downward velocity with which moved particles are initialized (last argument of EnableMovingPatch).
• Through EnableMovingPatch you can therefore change:
• “buffer_dist” – this is the (forward) distance from the moving body to the end of the current granular terrain patch at which a relocation of particles is triggered. The shorter this value, the longer the body will go before new particles are created in front of it (and the shorter the time those particles will have to settle before the body gets above the relocated particles).
• “shift_dist” – this is the dimension (in the forward direction) of the relocated block of particles.  The larger this value, the more particles are moved from “back” to “front”
• “init_vel” – this is the initial velocity given to all relocated particles when they are moved to the front. Usually, you would set this as a downward velocity to help the relocated granular material relocate.

 

--Radu

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