Transfer of angular momentum during oblique impact with(out) adhesion
I am solving a problem of 2 identical spherical particles colliding. The impact is oblique. I consider both normal and tangential contact forces. Tangential force is a combination of elastic force and friction.
I seems reasonable to me that after collision angular momentum should be the same for both particles, i.e. they start spinning in the same direction (particle B acting on particle A creates positive torque, particle A acting on particle B creates opposite force, but the sign of torque is the same). This also agrees with some experimental and theoretical results.
The problem starts when adhesion force is added. What happens with the momentum transfer once particles stick together and therefore cannot spin relative to each other?
It seems to me that they must start spinning as a whole. However I cannot physically reason it quite well.
Any suggestions?
UPDATE: thanks for your replies. This is indeed a complex problem. 782
To clarify some details: I am trying to follow a paper by Thornton & Yin, Powder Technology, 65 (1991), "Impact of elastic spheres with and without adhesion". I am timestep integrating all of the forces involved, i.e. collision is not instantaneous (~100-300 timesteps). When the particles stick due to adhesion there is the effect called "peeling", and this occurs until critical value of tangential force is reached. Then sliding starts (either a rigid body sliding, i.e. pure friction or micro-slip, which is a combination of elastic force and friction, as by <PERSON> and <PERSON> (1953), ASME J. Appl. Mech,20, p327).
I have my simulation match the results of <PERSON> and <PERSON> except the case of adhesion. The rebound angles (of particles' centres) match, so the model must be almost working, but the contact patch reflection angle does not (this one depends on spin of the particles caused by collision). This makes me think I am not implementing the transfer of angular momentum right in the case of sticking particles.
I will try to work out how to modify the angular momentum of the adhered pair from you replies and the paper you attached. 1002