This study examines how sudden expansions (ratios: 2.6, 1.56, 1.08) affect inertia and ambient water entrainment in density currents to evaluate their potential for flow control. Results show that sudden expansion consistently increases ambient water entrainment into the body, causing dilution and reduced concentration. This effect intensifies with expansion ratio, reaching a 4.7-fold entrainment increase and 37% concentration decrease for ratio 2.6. Despite this, due to the reduction in body height downstream of the expansion, increased width does not necessarily decrease body inertia. Depending on the experimental conditions, the expansion’s effect on the inertia can be amplifying in some cases and reducing in others. For example, for ratio 2.6 in a horizontal channel, body inertia decreased by 18.55%-37.45%, while on a 3% slope, it increased by 17.32%-45.17%. In contrast, the effect on head inertia, due to strong turbulent instabilities, is consistently reducing, with maximum reduction of 44.22% for ratio 2.6.
Ehdaei et al. (Wed,) studied this question.