Modeling of the Vortex Structure Inside a Ventilated Cavity

This work is devoted to the problem of modelling a forcibly ventilated gaseous cavity in a liquid flow. The relevance of the study is due to the need todevelop flow control methods in order to reduce drag. An analysis of literary sources showed that the internal structure of the flow inside the cavityremains poorly understood. This determines its shape, size and stability. A method for numerical modeling of unsteady 3D  two-phase flow in theopen-source software OpenFoam is proposed. The interFoam model was used for two incompressible fluids without phase transition. The mathematicalmodeling is based on the Volume of Fluid (VOF) approach. The computational mesh was constructed using the stepwise cell refinement methodusing the snappyHexMesh utility. The three-dimensional unstructured mesh consists mainly of hexa-elements. This takes into account small-scale flowstructures in the phase transition zone and near the streamlined body. The calculation results showed qualitative agreement with theoretical and experimental data. A complex vortex structure inside a ventilated cavity is described. Three zones are distinguished: constant pressure, viscous diffusion,and two-phase mixing layer. It was found that, unlike a steam supercavity, excess air behind the stable part forms a bubble trail. An analysis of the influenceof geometric and dynamic parameters on the formation and development of an air cavity, its size, shape, and stability was conducted. It was found that the lengths of the cavity zones depend on the velocity of the main fluid flow and the flow rate of the injected gas, and the thickness of thecavity is determined by the diameter of the cavitator. It has been shown that the constant pressure zone is extended and maintained due to forced ventilation.