Siphon Removal of Cohesionless Materials

This paper presents the results of an experimental study of the scour created by a siphon flow through a vertical tube of diameter $d$ of 9.7 to $20.4\mathrm{mm}$ in a cohesionless sand bed of approximately uniform size $D$ of $0.58\mathrm{mm}$ . The position of the inlet of the siphon tube ranged from $-101.6$ to $6.4\mathrm{mm}$ relative to the surface of the sand bed and the velocity of flow through the tube $U_0$ varied from 0.34 to $6.41\mathrm{m}∕\mathrm{s}$ . Data from this and previous studies are used to show the radial extent of the scour hole and the maximum depth of scour depend primarily on the densimetric Froude number ${\mathsf{F}}_0$ , where ${\mathsf{F}}_0=U_0∕\sqrt{g\left(\Delta \rho ∕\rho \right)D}$ , $g$ is the gravitational acceleration, $\Delta \rho$ is the difference in density between the sediment and fluid, and $\rho$ is the density of the fluid. A theoretical analysis of the problem is used to further assess the data and it is found that viscous effects are also important to consider. The profile of the scour hole at equilibrium, for all tube positions, is found to be similar when the scour depth is measured relative to the tube inlet.