Ambient Entrainment Mechanisms of Partially Unconfined Turbidity Currents Interacting with a Continuous Rigid Obstacle

Abstract

In this study, the entrainment mechanisms of unconfined turbidity currents that interact with a linear rectangular obstacle will be investigated and compared with confined studies. Laboratory experiments will be performed in a lock exchange basin, where the width allows unconfined and partially unconfined flows, with varying initial current densities. Ambient fluid entrainment, based on the Morton-Taylor-Turner (MTT) hypothesis, was found to be comparable to previous confined studies; however, in situ current density decreased at a greater rate than the latter. It was shown that this was probably caused by the unconfined lateral spreading of the current before the obstacle. The entrainment parameter had a weak relationship with Froude, Reynolds, and Richardson numbers for nonobstructed tests, which was similar to previous studies. However, this was not the case for obstacle tests, which experienced a greater variance in entrainment velocity and head height. Of note, head height was less than that for equivalent confined tests, which suggested that in a practical setting, confined studies might overestimate the obstacle height needed to block current propagation.