Gravity current flow past a circular cylinder: forces, wall shear stresses and implications for scour

Abstract

The flow of compositional gravity currents past circular cylinders mounted above a wall is investigated numerically. Two-and three-dimensional Navier-Stokes simulations are employed to quantify the force load on the cylinder, along with the friction velocity at the bottom wall near the cylinder, for Reynolds numbers in the range of 2, 000 − 45, 000. While two-dimensional simulations accurately capture the impact stage, they are seen to overpredict the force and friction velocity fluctuations throughout the transient stage.Comparisons between gravity current and constant density flows past circular cylinders show that the impact and transient stages are unique to gravity current flows. During the quasisteady stage, on the other hand, the wake structures and the values of the drag, the peak-to-peak lift, the vortex shedding frequency, and the friction velocity below the cylinder are comparable.The friction velocity below the cylinder depends chiefly on the Reynolds number formed with the front velocity and the gap width. The maximum friction velocity at impact is about 60% larger than during the quasisteady stage, or in a constant density flow. This raises the possibility of aggressive erosion behavior at impact, which may occur in a spanwise localized fashion due to the larger friction velocity near the lobes.

TURBINS: An immersed boundary, Navier–Stokes code for the simulation of gravity and turbidity currents interacting with complex topographies

“…This will help our understanding of the processes governing the formation of large-scale sediment deposits in the deep oceans, which in turn is highly relevant with regard to hydrocarbon exploration. TURBINS can also address the unsteady, nonlinear interaction of density-driven currents with submarine structures such as pipelines or well heads, and evaluate the forces and time scales arising during such interactions [15]. Furthermore, accurate depth-resolved simulations performed by TURBINS can aid in the validation of conceptually simpler depth-averaged or shallow water models of flows over complex topography, e.g.…”

Circulation-based models for Boussinesq internal bores

“…In the atmosphere, they arise from the interaction of sea-breezes or thunderstorm outflows with inversion layers (Clarke, Smith & Reid 1981;Haase & Smith 1984;Wakimoto & Kingsmill 1995). In marine environments, they can be caused by the breaking of internal waves (Leichter et al 1996), by tides interacting with seafloor topography (Morozov et al 2002), or by gravity current flows past submarine obstacles (Gonzalez-Juez et al 2010). Several analytical models have been proposed to relate the speed of propagation of a bore to…”

Internal bores: an improved model via a detailed analysis of the energy budget

“…In marine environments, internal bores can arise from the breaking of internal waves (Leichter et al 1996), by the interaction of the tides with ocean floor topography (Morozov et al 2002), and by gravity current flows past submarine obstacles (Gonzalez-Juez, Meiburg & Constantinescu 2009;Gonzalez-Juez et al 2010). These marine bores can have a substantial impact on the local environment.…”