Unstructured Nonlinear Free Surface Flow Solutions: Validation and Verification

Abstract

A nonlinear free surface solution methodology is incorporated within an existing three-dimensional, unstructured Navier-Stokes solver, . This portable, parallel solver uses a node-based finite volume method to solve the incompressible Reynolds-averaged NavierStokes equations on mixed element high-aspect ratio grids, includes several turbulence models to simulate the affects of turbulence within the boundary layer, and has the capability to simulate flow through rotating propellers accurately. To obtain a nonlinear free surface, the kinematic free surface equation is solved at each time level via a finite element implementation, valid on both triangles and quadrilaterals; after several time steps (approximately 200), the grid is moved to match the free surface elevations while conforming to the geometry. Robust grid movement is achieved by using a three-dimensional extension of Farhat’s torsional spring analogy. Validation studies include a grid refinement for the free surface on a circle based on a prescribed velocity field, and of flow around a submerged NACA0012 hydrofoil. For the NACA0012 hydrofoil, for the viscous and inviscid Wigley hull and for the DTMB Model 5415 series hull, wave profiles along the hull are compared against available experimental results as well as numerical results from a more mature structured nonlinear free surface code UNCLE.