Computational investigation of scour characteristics of USAF in multi-specie sand under steady current

Abstract

The seabed sediment in marine is typically composed of complex mixtures of materials thereby it is of paramount importance to consider a multi-specie sand bed in scouring tests since most of the researches only take individual specie sand bed into account. In this work, a series of scouring tests were conducted computationally by using a VOF method to capture the sharp interface and finite-volume-finite-difference method to solve the RANS equation combined with sediment transport equations, with the purpose of investigating the characteristics of local scour around a novel offshore foundation, USAF, in a multi-specie (two-specie) sand seabed under steady current state. The three-dimensional scour model was established and validated against available experimental data. Furthermore, the effect of very fine sand on the scouring process in medium sand sediment bed is clarified. Meanwhile, the influence of the Froude number is also determined. The predicted results suggest that scour characteristics in the multi-specie sand seabed is significantly different from that in sole one, which depends on both amount of very fine sand and Froude number.