19. Transient CFD Simulation of Vortex Formation in a Stirred Multiphase Flow

The present study simulated the dynamic behavior of the water–air interface in a cylindrical tank stirred mechanically. CFD techniques were applied using the software ANSYS-Fluent. The Volume of Fluid (VOF) model with explicit formulation coupled to the \(\upkappa \)-\(\upomega \) SST turbulence model was employed to numerically represent the transient displacement of the water–air interface starting from a situation of stagnated flow. An isothermal operation was considered for the case studied. A simple experimental apparatus composed of a glass vessel filled with dyed water and a mechanical stirrer with a pitched-bladed impeller was used to generate the experimental data of the interface position along the time. The model accuracy was evaluated at stirring rates of 300 and 400 RPM. According to the results, the geometric shape profile of the vortex at the pseudo-stationary state could be reasonably well reproduced by the model. However, the model could not generate accurate results regarding the transient behavior of the vortex formation. Additional strategies should be tested to enhance the model capability to reproduce the transient displacement of the water–air interface due to the rotational flow.