An improved Mesh Adaption and Refinement approach to Cavitation Simulation (MARCS) of propellers

Abstract

This paper presents the improvements of cavitation modelling for marine propellers particularly developing tip vortex cavitation. The main purpose of the study is to devise a new approach for modelling tip vortex cavitation using Computational Fluid Dynamics (CFD) methods with commercial software, STAR-CCM+. The INSEAN E779A model propeller was used for this study as a benchmark propeller. Utilizing this propeller, firstly, validation studies were conducted in non-cavitating conditions together with grid and time step uncertainty studies. Then, the cavitation was simulated on the propeller using a numerical cavitation model, which is known as the Schnerr-Sauer model, based on the Rayleigh-Plesset equation. While a Reynolds Averaged Navier Stokes (RANS) model was used for open water simulations, Detached Eddy Simulations (DES) and Large EddySimulations (LES) models were preferred for cavitation simulations to capture the cavitation and evaluate its effect on propeller performance accurately. Although the comparison with the benchmark experimental data showed good agreement for the thrust and torque coefficients as well as sheet cavitation pattern, tip vortex cavitation could not be adequately simulated using the existing method. After an evaluation of the interaction between cavitation modelling and generated meshes, two techniques, which involved volumetric control and adaptive mesh refinement, were used in combination on the region where the tip vortex cavitation is likely to occur. The first technique, which is called a 'volumetric control method', was developed using spiral geometry around the propeller tip region to generate a finer mesh for capturing tip vortex cavitation. Although this method gave better tip vortex cavitation extension than the method without any mesh refinement or with tube refinement, it still required to be improved to extend the tip vortices further into the propeller slipstream.The second method, which is called 'adaptive mesh refinement', was introduced using the pressure distribution data from the results of the 'volumetric control method'. This improved approach, which is called "Mesh Adaption and Refinement for Cavitation Simulation (MARCS)", has been successfully applied to simulate the tip vortices trailing from the blades of the INSEAN E779A propeller as demonstrated in the paper. The results of the simulations showed an excellent agreement with the experiments in the open literature by tracking the tip vortex cavitation along this propeller's slipstream.

Suppression of Tip Vortex Cavitation Noise of Propellers using PressurePoresTM Technology

“…An adaptive mesh refinement technique for evaluating the impacts of these variations on the propeller performance (K T , K Q and η 0 ) in cavitating flow conditions was used. In these investigations, the pore configurations applied were simulated initially by using a non-optimised TVC model but later using the advanced adaptive mesh refinement technique of Yilmaz et al [16] as described and discussed in Section 4.…”

“…An advanced mesh refinement technique for capturing tip vortex cavitation in a propeller slipstream was proposed [20], where preliminary results were presented for a limited range of tip vortex extensions for two benchmark propeller models (PPTC and INSEAN E779A). The method was further developed by using the INSEAN E779A propeller, allowing a greater extension of the TVC in the propeller slipstream to be achieved [16]. This mesh refinement approach (MARCS) was further applied on The Princess Royal propeller model, capturing an even greater extension of the tip cavitating tip vortex development in the propeller slipstream [21].…”

“…and estimated the uncertainty values for the calculations. This analysis method had been previously applied for non-cavitating and cavitating propellers, including the intact model of The Princess Royal [16,21].…”

A Numerical Investigation of a Winglet-Propeller Using an LES Model

“…They pointed out that the TVC was excellently captured with the detached eddy simulation (DES). Yilmaz et al [12] developed an adaptive mesh refinement approach with absolute pressure as a control parameter in order to more accurately simulate TVC in the wake of a propeller. Posa et al [13] studied the wake characteristics of a submarine propeller using a large eddy simulation (LES) model; they showed that the coherence structures shed from the inner radii of the blades were stronger than those from the outer radii.…”

“…In contrast, the DES model could track the field of a tip vortex for a long distance and successfully predict the instabilities in the wake, which was in good quantitative and qualitative agreement with experiments. In addition, after comparing the cavitation characteristics between the DES model and the LES model, Yilmaz et al [12] concluded that the LES model was the preferred model for investigating TVC. In contrast to the RANS equations, the equations that are solved for a LES are obtained by a spatial filtering rather than an averaging process.…”