Numerical Simulation of Free Surface Flows Using Overset Mesh

Abstract

Overset method is validated for different free surface flow applications to demonstrate its capabilities and benefits over traditional dynamic mesh approach. An overset mesh consists of a set of overlapping component meshes, which allows complex geometries to mesh with lesser effort. Interpolation methods are enforced at internal boundaries to ensure a continuous solution in overlapping component zones. Overset methodology is not perfectly mass conservative by its design. Present study in this regard, demonstrates the benefit of higher order interpolation method on simulation accuracy and mass conservation. The simulation results for various case studies involving static and moving overset meshes are validated against analytical, experimental and equivalent non-overset mesh results using ANSYS Fluent. Finite volume method (FVM) with pressure based coupled solver is used to solve Reynolds Averaged Navier Stokes equations. Free surface flow is modeled using Volume of Fluid Method (VOF) which capture interfaces between immiscible fluids. Pseudo-transient method is adopted for steady state applications to get better robustness. A pure advection of slotted circle is simulated where its revolution is forced along the static overlapping zone, final shape and position is compared with initial state after one revolution. A non-linear Stokes wave with high steepness is propagated in a numerical wave tank which contains multiple static overlapping zones in the vicinity of free surface, where simulation results of free surface and velocity profiles are verified against analytical profiles. Flow over a bump for subcritical to subcritical and subcritical to supercritical regimes are verified against analytical results. Flow over a submerged hydrofoil using static overset mesh is validated against experimental result for free surface profile. A rotating gear case involving moving overset mesh is compared with sliding mesh results for free surface and pressure profiles. A case involving transient heave oscillation of floating cylinder is validated with theoretical, experimental and equivalent dynamic mesh results.

Wing Sails: Numerical Analysis of High-Performance Propulsion Systems for a Racing Yacht

“…The 2D simulations are mainly devoted to the selection of the most efficient designs from the point of view of lift-to-drag ratio. The 3D analysis mostly revolves around the flow phenomena analysis around a moving yacht using a contemporary approach of the overset mesh [15], which has not been employed to date for similar, high-fidelity studies. In this technique, the component meshes (sails and hull in this case) are blended into the background mesh (external flow domain) using a dedicated script [16].…”

Impact of Stepped Structures on Tsunami Wave Propagation and Overtopping Engineering

“…In the present study, the k-ε turbulence model, as proposed by Khaware et al [21], Wei et al [25], and Luo et al [27], has been selected for application. This model currently enjoys widespread usage in the simulation of turbulent flow conditions.…”

“…To solve this model, the PISO scheme is used for pressure velocity coupling, for calculations momentum and volume fraction we utilize second-order upwind and compressive schemes, respectively [18,20,21]. First-order transient methods are employed using an Explicit formulation.…”

“…Its adoption by numerous researchers attests to its utility. Studies like those performed by Khaware et al [21] have explored the sensitivity of 5th order solitary wave models in shallow wave environments. Findings from these investigations suggest that the application of Stokes wave theory remains viable within the shallow regime, and the Explicit formulation is particularly sensitive to breaking conditions, necessitating a very small step size.…”

Numerical Analysis of an Overtopping Wave Energy Converter Subjected to the Incidence of Irregular and Regular Waves from Realistic Sea States

“…From that, the numerical beach is considered as a region with its end surface as the open channel pressure outlet boundary (hydrostatic profile), which is parallel to its initial surface (start line of the gray region in the wave channel, in Figure 5). In addition, the direction of the numerical beach is normal to its initial and end surfaces, with the damping effect increasing gradually from the beginning of the numerical beach until its final boundary [45,46].…”