NUMERICAL MODELING OF AERATED CAVITATION USING A PENALIZATION APPROACH FOR AIR BUBBLE MODELING COUPLED TO HOMOGENEOUS EQUILIBRIUM MODEL

Cavitation is a well-known physical phenomena occurring in various technical applications. It appears when the pressure of the liquid drops below the saturation pressure. Coupling aeration in a cavitating flow is a recent technique to control the overall effect of the cavitation. It is achieved by introducing air bubbles into the flow. In order to reveal and explore the behaviour of air gas in the vicinity of the cavitation region, the paper is oriented towards the physics of the colliding vapor phase bubbles and cavitating regions. The re-entrant jet may influence the dynamics of the bubbles as well as the frequency of cavitation separation. Therefore, a two-way coupling between the fluid flow and the introduced vapor is of capital importance. By penalizing the strain rate tensor in the Homogeneous Mixture Model, the two-way coupling has been achieved. The contact-handling algorithm is based on the projections of the velocity fields of the injected particles over the velocity field of the fluid flow. At each time step the gradient of the distance between the bubbles, is kept non-negative as a guarantee of the physical non overlapping. The bubbles' collisions are considered as inelastic. The differential equations system is composed of the Navier-Stokes equations, implemented with the Homogeneous Mixture Model. A high-order Finite Volume (FV) solver based on Moving Least Squares. (MLS) approximations is used. The code uses a SLAUtype Riemann solver for the accurate calculation of the low Mach numbers. The computational domain is a symmetrical 2D venturi duct with an 18 degrees - 8 degrees convergent/divergent angles respectively.