We consider a sheet flow in which heavy grains near a packed bed inter
act with a unidirectional turbulent shear flow of a fluid. We focus on
sheet flows in which the particles are supported by their collisional
interactions rather than by the velocity fluctuations of the turbulen
t fluid and introduce what we believe to be the simplest theory for th
e collisional regime that captures its essential features. We employ a
relatively simple model of the turbulent shearing of the fluid and us
e kinetic theory for the collisional grain flow to predict profiles of
the mean fluid velocity, the mean particle velocity, the particle con
centration, and the strength of the particle velocity fluctuations wit
hin the sheet. These profiles are obtained as solutions to the equatio
ns of balance of fluid and particle momentum and particle fluctuation
energy over a range of Shields parameters between 0.5 and 2.5. We comp
are the predicted thickness of the concentrated region and the predict
ed features of the profile of the mean fluid velocity with those measu
red by Sumer et al, (1996). In addition, we calculate the volume flux
of particles in the sheet as a function of Shields parameter. Finally,
we apply the theory to sand grains in air for the conditions of a san
dstorm and calculate profiles of particle concentration, velocity, and
local volume flux.