[Abeer]

Hello everyone,

I am using DEM collision model where I predefined few particles with density of 2650 Kg/m^3 inside the pipe, The pipe diameter = 0.0042m, length L= 1m.
Particle initial conditions can be read from an external file. at time = 0, (334) particles are placed at random position within the pipe. The velocity of the particles in radial direction is chosen randomly from -v to v= 0.01, while the particle velocity in axial direction is set to zero.
The collision parameters for the collision pairs was Herzian_dashpot for normal contact force and friction_dshf_rolling for tangential force.
Periodic boundary condition is applied in the axial direction with specified air mass flow in same direction of zero Kg/s.
Transient model, with unsteady particle tracking, and the gravity was activated, so the particles are falling in the axial direction.
I have run 334 particles for 10000-time steps, with 0.0001s time step size. The solution was successfully converged, but the calculation time took extremely long time (more than 24 hrs. for 40% Iteration).
According to the calculation of collision time and martial properties mentioned above, I should use time step size about 10^-5, with 100000-time steps, which supposed to have longer iteration time.

I appreciate any advice on setup and/ or parameter that can help in reducing the iteration time. Thanks in advance.

Abi