The stress generated by non-Brownian fibers in turbulent channel flow simulations
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Abstract
Turbulent fiber suspension channel flow is studied using direct numerical simulation. The effect of the fibers on the fluid mechanics is governed by a stress tensor, involving the distribution of fiber position and orientation. Properties of this function in channel flow are studied by computing the trajectories and orientations of individual particles, referred to as the particle method. It is shown that, due to computer restrictions, the instantaneous stress in channel flow cannot be simulated directly with the particle method. To approximate the stress we compute the second-order moment of the fiber distribution function. This method involves an unknown subgrid term, which is modeled as diffusion. The accuracy of the moment approximation is studied by comparing Reynolds averaged stress to results obtained from the particle method. It is observed that the errors are ? 1% for y+>20, and ? 20% for y+