viscous drag of a wall

Hi Thomas,

Thanks for the question. I presume you are looking for frictional walls. Unfortunately we do not have a frictional wall interaction group at present although it would certainly come in handy! In most cases, this can be worked around by bonding a layer of particles to a wall and defining frictional interactions between those particles and other particles in the model. There's an example of how to do this in the updated ESyS-Particle tutorial:
http://www.uq.edu.au/~uqdweath/ESyS_Particle_Tutorial.pdf

I'll add frictional/viscous walls to the list of desired features.

Cheers,

Dion.

Unfortunately its not quite as simple. "Viscous" and "frictional" walls are quite different, not only from a physical point of view (velocity dependent drag force vs. stress dependent) but also from an implementation point of view. Viscous interactions would just need the velocities of the particle and the wall (and some indication if the particle is close enough to the wall to be dragged) and therefore carry no state which means they are easier to deal with regarding the exchange of data between workers (see CEWallInteractionGroup<T>::Update(..) vs CBWallInteractionGroup<T>::Update(..) ). OTOH walls currently have no proper concept of velocoty, or, more precisely the velocity one can set via setVelocityOfWall() is not coupled to the actual movement of the wall (via moveWallBy()). If a function was to be implemented which calculates the current velocities from its movement one would need to take into account that wall move both due to moveWallBy() and also due to applyForceToWall().
Frictional interactions, OTOH, don't need velocities, just displacements - so there would be no need to deal with the wall velocity. However, it would be neccessary to deal with the exchange of the interaction state between worker processes. Also , one would probably need both a rotational and a non-rotational variant.

Steffen