  The Fluctuating Force Fluctuating Torque (F3T) model is developed and
evaluated for the dynamics of a turbulent particle-gas suspension of rough
spherical particles in a turbulent Couette flow in the limit where the viscous
relaxation time of the particles and the time between collisions are much
larger than the integral time for the fluid turbulence. The fluid force/torque
exerted on the particles comprise a steady part due to the difference in the
particle velocity/angular velocity and the fluid mean velocity/rotation rate,
and a fluctuating part due to the turbulent velocity/vorticity fluctuations.
The fluctuations are modeled as Gaussian white noise whose variance is
determined from the fluid velocity and vorticity fluctuations. The smooth and
rough inelastic collision models are considered for particle-particle and
particle-wall collisions. The results show that inclusion of roughness is
important for accurately predicting the particle dynamics; the second moments
of the velocity fluctuations for rough particles are higher than those for
smooth particles by a factor of 2-10, while the second moments of the angular
velocity fluctuations are higher by 1-2 orders of magnitude. The F3T model
quantitatively predicts the number density, mean and root mean square velocity
and angular velocity profiles, and the distribution functions for the particle
velocity and angular velocity, even though a Gaussian model is used for the
highly non-Gaussian distributions for the force and torque fluctuations.
