Predicting Sand Deposition at Porous Fences

For porous fences of limited height and infinite length, measurements of boundary shear stress are reported in air flow normal to the fence plane. On the assumption that boundary shear stress is similarly distributed in sand-laden flow, calculations are made of the growth of a dune near a fence placed normal to the transport direction of sand. Although based on formulas developed for circumstances of uniform flow and transport rate, the calculations are reasonably successful when compared with small-scale wind-tunnel experiments. It is shown that the effect of jetting through fence gaps should be allowed for in calculations and that this can be done quite simply, and also that each sand (and by implication each sand condition) requires its own transport rate formula. Grain collisions with fence members and the effect of probable miscalculation of characteristic path length are examined but not resolved.