Turbulent gravity current of lock release type: A numerical study

Tbe time evolution of a turbulent gravity current of lock release type, formed by a finite volume of homogenous fluid released instantaneously into anot her fluid of slightly lower density, is studied numerically via the renormalization group (RNG) k - f model for Reynolds-Stress closure to characterize the flow with transitional and highly localized turbulence. Consistent with previous experimental observations, the numerical results show that the gravity current passes through two distinct phases, an initial slumping phase in which the current head advances steadily, and a second self-similar phase in which the front velocity decreases like the negative third power of the time after release. An overall entrainment ratio proportional to the distance from the release point is found and compares well with available experimental data for the slumping phase.