A finite element framework for fluid-structure interaction of turbulent cavitating flows with flexible structures

Abstract: We present a finite element framework for the numerical prediction of cavitating turbulent flows interacting with flexible structures. The vapor-fluid phases are captured through a homogeneous mixture model, with a scalar transport equation governing the spatio-temporal evolution of cavitation dynamics. High-density gradients in the two-phase cavitating flow motivate the use of a positivity-preserving Petrov-Galerkin stabilization method in the variational framework. A mass transfer source term introduces local compressibility effects arising as a consequence of phase change. The turbulent fluid flow is modeled through a dynamic subgrid-scale method for large eddy simulations. The flexible structure is represented by a set of eigenmodes, obtained through the modal analysis of the linear elasticity equations. A partitioned iterative approach is adopted to couple the structural dynamics and cavitating fluid flow, where the deforming flow domain is described by an arbitrary Lagrangian-Eulerian frame of reference. Through the numerical validation study, we establish the fidelity of the proposed framework by comparing it against experimental and numerical studies for both rigid and flexible hydrofoils in cavitating flows. Based on the validation study conducted over a flexible NACA66 rectangular hydrofoil, we elucidate the role of cavity and vortex shedding in governing the structural dynamics of a flexible hydrofoil.