Effective Wall Friction in Wall-Bounded 3D Dense Granular Flows

A method for estimating wall friction in turbulent wall-bounded flows

We describe a simple method for estimating turbulent boundary layer wall friction using the fit of measured velocity data to a boundary layer model profile that extends the logarithmic profile all the way to the wall. Two models for the boundary layer profile are examined, the power-series interpolation scheme of Spalding and the Musker profile which is based on the eddy viscosity concept. The ...

Effective boundary conditions for dense granular flows.

We derive an effective boundary condition for dense granular flow taking into account the effect of the heterogeneity of the force network on sliding friction dynamics. This yields an intermediate boundary condition which lies in the limit between no slip and Coulomb friction; two simple functions relating wall stress, velocity, and velocity variance are found from numerical simulations. Moreov...

Skin Friction in Simple Wall - Bounded Shear Flows in Large Reynolds Number Limit

Expressions for variation of skin friction with Reynolds number in fully developed turbulent channel/pipe flows and in zero pressure gradient boundary layers are derived. The proposed in this paper asymptotic (Reδ = δ(x)U ν → ∞) theory is formulated as a convergent perturbation expansion in powers of small dimensionless parameters dδ dx → 0 and u∗ U → 0 applied directly to the Navier-Stokes equ...

The effect of sidewall friction on dense granular flows

We present novel results on flow properties using molecular dynamics simulation as well as γ -densitometry experiments. We show that fundamentally different types of granular flow can be observed in one unique system. Using both frictional and frictionless confining walls, we show that the differences existing between these regimes originate in the frictional properties of the walls. The salien...

The topology of skin friction and surface vorticity fields in wall-bounded flows