Scour Around Spherical Bodies and Self-Burial

This paper summarizes the results of an experimental study on scour around spherical bodies and self-burial in steady current and in waves. The equilibrium scour depth below a fixed sphere in steady current for live-bed conditions was found to be $S∕D=O\left(0.3\right)$ , $D$ being the sphere diameter. The effect of the Shields parameter, $\theta$ , and that of the position of the sphere with respect to the bed, $e$ , were investigated. It was found that, under live-bed conditions, the effect of $\theta$ is quite weak. It was also found that the effect of $e$ is significant. No scour occurs when $e∕D>0.8$ . It was demonstrated that, in the case of waves, the Keulegan-Carpenter number, $\mathsf{K}\mathsf{C}$ , is the main parameter that governs the equilibrium scour depth. $S∕D$ is always smaller in waves than in steady currents. Regarding the self-burial, the equilibrium self-burial depth in steady current was found to be $e∕D=O\left(0.5\right)$ . The self-burial depth in waves is governed by $\mathsf{K}\mathsf{C}$ , similar to the scour depth for a fixed sphere. $e∕D$ is always smaller in waves than in steady currents. The experiments indicated that the time scale of both the scour process and the self-burial process is a function of $\theta$ in the case of steady current, and $\theta$ and $\mathsf{K}\mathsf{C}$ in the case of waves.