Documentation of tangential coefficient of restitution in StandardWallInteraction is incorrect

Summary

Documentation of tangential coefficient of restitution in StandardWallInteraction.H is incorrect.

The documentation in the header says " mu 0; // optional - restitution coeff"

However, if you set mu = 1 then line 234 (v2212) results in the tangential velocity being reduced to zero which is what you should get for a perfectly inelastic collision, i.e. a coefficient of restitution of 1. " U -= mu_*Ut;"

What is the current bug behaviour?

Setting a value of mu = 1 behaves as a perfectly inelastic collision instead of a perfectly elastic collision.

What is the expected correct behavior?

Setting a value of mu = 1 should not alter the tangential velocity upon impact with the wall. Conversely setting mu = 0 should reduce the particle tangential velocity to that of the patch.

Possible fixes

The documentation should state the mu is equal to 1 minus the coefficient of restitution. This is how it is implemented in the code.

Or the code (line 234) should be changed so that mu behaves as a coefficient of restitution.