A viscous vorticity method for the prediction of turbulent flows around hydrofoils and propellers

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Marine propellers operate in turbulent flows, presenting a significant challenge for numerical analysis and design. Conventional linear and potential flow theories have limitations in predicting turbulent flows. Viscous flow methods, though capable of handling turbulence by incorporating a turbulence model, are often computationally intensive. The primary objective of this dissertation is to develop an efficient viscous numerical solver for simulating turbulent flows around propellers. The VIScous Vorticity Equation (VISVE) numerical solver was previously developed to handle laminar flow problems. This dissertation aims to extend this solver to allow for turbulence modeling and cavitation. The focus is on implementing the k − ω SST turbulence model in both 2-D and 3-D versions of the VISVE solver. The turbulence model is discretized using the Finite Volume Method (FVM), and a hybrid OpenMP/MPI parallelization strategy is adopted to fully leverage High-Performance Computing (HPC) resources. The developed method is first applied to 2-D hydrofoils in turbulent flow, showcasing excellent agreement with predictions from a Reynolds-Averaged Navier-Stokes (RANS) solver. The influence of Reynolds number (Re) on vorticity, velocity, and turbulent viscosity is studied across a range of Re values. The turbulent VISVE model is also successfully applied to a hydrofoil with a cupped trailing edge, capturing turbulent separated flow at high Reynolds numbers. The method is then extended to 3-D analysis, demonstrating consistency with RANS solver results for infinitely long hydrofoils and rectangular wings. The turbulent VISVE solver is further employed to study propellers in turbulent flow, with a focus on a 5-bladed propeller (e.g., the NSRCD propeller 4381) under various loading conditions. In addition to investigating 2-D and 3-D turbulent flow scenarios, the 2-D solver is extended to address turbulent cavitating conditions. A pressure calculation scheme is proposed for 2-D turbulent and cavitating flow, and multiphase and cavitation models are implemented in the 2-D turbulent VISVE solver, using the mixture model. Scalability tests are conducted to optimize computational resources, enhancing the solver’s efficiency. Notably, the VISVE method offers advantages such as a significantly smaller computational domain and post-processing pressure calculation. Moreover, the computational grid size, unknowns, and computation time for the propeller system are significantly reduced by considering the effects of all other blades using the key blade’s solution from an earlier time step. Overall, this research contributes to the development of a robust and efficient numerical solver for simulating turbulent flows around hydrofoils and propellers. The implementation of turbulence models and parallelization strategies advances the understanding and analysis of turbulent propeller flows, with potential applications in marine propulsion design and performance analysis.


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