Turbulence and multiphase modelling of oil-in-water dispersions in stirred cells

During the blowout of a subsea oil well, the fate and sequestration of the oil depends strongly on the size of the droplets. The distribution of the droplet sizes is determined by the turbulence of the flow field, the interaction between the phases present in the flow and the conditions at the well head. As full scale experiments are not tractable, benchtop and pilot-scale experimental investigations have been designed to measure oil droplet sizes under varying shear conditions. To better characterise the turbulence generated under these laboratory conditions, we have deployed a Finite Volume Method (FVM) to numerically simulate turbulence generated in a sapphire autoclave apparatus. To validate the turbulence models, a test condition was simulated for a single-phase baffled tank, where fluid motion was maintained by a Rushton turbine operating at Reynolds number of 7300. Results from a Wall Modelled Large Eddy Simulation (WMLES) were compared against the published experimental and Wall Resolving LES data. This method, along with a multiphase model, has been applied to simulate an autoclave system in which a four-blade vane-and-baffle mixing impeller was used to disperse oil in saltwater at high pressure. The speed of the impeller blade was varied to simulate Reynolds numbers ranging from 1073 to 5378, facilitating comparison between the model results and the experimental data.