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7 results on '"Robb, Daniel M."'

1. The Dynamics of Asymmetric Stratified Shear Instabilities

Author

Olsthoorn, Jason, Kaminski, Alexis K., and Robb, Daniel M.

Subjects
Physics - Fluid Dynamics
Abstract

Most idealized studies of stratified shear instabilities assume that the shear interface and the buoyancy interface are coincident. We discuss the role of asymmetry on the evolution of shear instabilities. Using linear stability theory and direct numerical simulations, we show that asymmetric shear instabilities exhibit features of both Holmboe and Kelvin-Helmholtz (KH) instabilities, and develop a framework to determine whether the instabilities are more Holmboe-like or more KH-like. Further, the asymmetric instabilities produce asymmetric mixing that exhibits features of both overturning and scouring flows and that tends to realign the shear and buoyancy interfaces. In all but the symmetric KH simulations, we observe a collapse in the distribution of gradient Richardson number ($Ri_g$), suggesting that asymmetry reduces the parameter dependence of KH-driven mixing events. The observed dependence of the turbulent dynamics on small-scale details of the shear and stratification has important implications for the interpretation of oceanographic data., Comment: 9 Figures, 21 pages

Published
2022

6. Turbidity variations in the epilimnion of a glacier-fed reservoir.

Author

Robb, Daniel M., Pieters, Roger, and Lawrence, Gregory A.

Subjects
GLACIERS, TURBIDITY, RESERVOIRS
Abstract

We have been investigating the variation of turbidity in the surface waters of Carpenter Reservoir, British Columbia, Canada. This long (~50 km) and narrow (~1 km) reservoir receives glacially-turbid meltwater, and there is concern that this turbidity limits light availability in the reservoir and, in turn, limits biological productivity. To address these concerns, we use a combination of field observations, numerical simulations and analytical scaling arguments. Vertical profiles of temperature and turbidity indicate that during summer, inflows plunge below the thermocline and travel along the bottom of the reservoir. The load of glacial particles entering the reservoir is highest in summer, yet turbidity in the epilimnion declines due to thermal stratification isolating the epilimnion from plunging glacial inflows and suspended particles settling from the epilimnion to the hypolimnion. However, episodic wind events upwell turbid fluid to the surface waters. Numerical simulations support the notion that wind-driven upwelling in summer contributes to a small turbidity flux into the epilimnion. Changes in turbidity along the length of the epilimnion are determined by wind-driven fluxes, longitudinal dispersion and particle settling. [ABSTRACT FROM AUTHOR]

Published
2023

7. SPH-DEM model for free-surface flows containing solids applied to river ice jams.

Author

Marongiu, Jean-Christophe, Robb, Daniel M., and Gaskin, Susan J.

Subjects
*DISCRETE element method, *OPEN-channel flow, *ICE jams (Geology), *BULK solids flow, *CHANNEL flow, *HYDRODYNAMICS
Abstract

A meshless method is used to simulate free-surface fluid flows containing solid particles, motivated by the need to simulate river ice dynamics problems. A smoothed particle hydrodynamics model (SPH), with an arbitrary Lagrangian–Eulerian formulation for the fluid phase, is two-way coupled with the discrete element method (DEM) for the solid phase. Validation test cases include a bouncing sphere on a level surface, a collapse of a granular column, wedge entry into still water and solids of different densities falling into still water. The computed results using the SPH-DEM model agree quantitatively with the expected behaviour in the test cases. Numerical convergence is demonstrated for the wedge entry validation case. The SPH-DEM model is then used to simulate the stability of floating ice blocks approaching a stationary cover and ice accumulation upstream of an obstruction. The results show promise to serve as a useful quantitative engineering tool. [ABSTRACT FROM PUBLISHER]

Published
2016
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