Analysis of Turbulent Modeling for Free‐Surface Flows Using a Hybrid RANS ‐ LES Model and Particle‐Based Moving Particle Semi‐Implicit Method

Engineering problems often comprise free‐surface flows in turbulent regime. Lagrangian mesh‐free particle‐based methods are well suited for the simulation of flows involving complex free‐surface deformation. However, the analysis of turbulent modeling for particle‐based methods is relatively scarce in the literature. In this work, an analysis of a hybrid RANS‐LES turbulence model adapted for the Moving Particle Semi‐implicit (MPS) method is performed. In the turbulence model, a zero‐equation RANS is applied near the wall boundaries and a standard Smagorinsky LES model is applied elsewhere. Given that the eddy viscosity of the turbulent modeling depends on the distance between the fluid and the nearest wall particle, the calculation of the fluid‐wall particle distance may demand a high computational cost due to undefined topology among moving particles. In this way, a method based on the cell‐linked list is proposed to improve the nearest wall search for the turbulence model. The implementation is verified through simulation of a lid‐driven flow with Reynolds number between and . The result shows that despite the overhead when the turbulence model is adopted, the time needed to reach steady state is shortened so that the overall computational costs are almost the same. In addition, the improvement due to the adoption of turbulence model is more evident for the highest Reynolds numbers. As an application, the flow around a submerged square cylinder near the surface with Reynolds number of is simulated. The influences of the cylinder submergence depths on the drag and lift coefficients are investigated for a range of depth‐to‐length ratios between and . When the turbulence model is applied, a smoother convergence tendency is obtained as the resolution increases. Moreover, the flow around the square cylinder is better represented, resulting in more regular vortex shedding. Different flow behaviors were identified around the square cylinder as the submergence depth changes.