Application of eddy-viscosity turbulence models to problems in ship hydrodynamics

Abstract

With the rapid advent of computational methods in all fields of engineering, several areas have emerged as significant sources of ambiguity. Among these is the selection of a turbulence model to close the Reynolds averaged Navier-Stokes equation. In ship hydrodynamics, this has been particularly difficult to resolve due to the complex nature of the problem. Furthermore, there are a wide variety of turbulence models all claiming superiority. Thus, navigating to the correct choice is a subject of experience. The present study aims to alleviate the ambiguity inherent in the field. This is done by performing a series of tests on the turbulence models and comparing the integral outcomes with experimental results. Specifically, shallow water cases are chosen due to the additional layer of complexity associated in the prediction of parameters of interest. The results are analysed via a modified bivariate plot, which reveals a strong candidate for the optimum choice of turbulence modelling. The assessment simultaneously takes into account resistance and sinkage, in addition to consistency across different casestudies. The time per iteration also points towards the same candidate, identified as the standard k-ω model, as a good choice within the software used to perform the analysis. The results also suggest that pressure resistance and its constituent components are not coupled with the turbulence model. On the other hand, frictional resistance is highly dependent on the closure selected and is identified as the main contributor to deviations with regards to experimental values. Abe et al. (1994) proposed a modification of the standard k-ε model, henceforth referred to as 'AKN'

Propeller Performance Penalty of Biofouling: Computational Fluid Dynamics Prediction

“…A verification study was conducted to assess the numerical uncertainties of the CFD models and to determine sufficient grid-spacing. The Grid Convergence Index (GCI) method based on the extrapolation of Richardson [49] was used to estimate the order of accuracy of the simulations, as similarly used by [50][51][52][53]. According to Celik et al [54] the apparent order of the method, , is determined by for a spatial convergence study of a 3D model.…”

Numerical and experimental study on hydrodynamic performance of ships advancing through different canals

“…Firstly, shallow water flows are highly three-dimensional. As demonstrated recently by Terziev et al (2019b), the boundary layer of the ship is predicted to come in contact with the seabed in very shallow water cases. This brings about the second difficulty, referred to previously, namely, non-linear effects.…”

“…The present study will also serve to validate the assertion that the k -ω turbulence model provides good predictions over a greater range of case-studies. The expectation is that the resistance will be predicted with a small, negative error based on previous experience (Terziev et al, 2019b). The temporal term of the Navier-Stokes equations is discretised via a 1 st order accurate scheme, with a time-step of t=0.0035×L/V, following Tezdogan et al (2016).…”

Virtual Replica of a Towing Tank Experiment to Determine the Kelvin Half-Angle of a Ship in Restricted Water

“…Turbulence modelling is also a source of error in the results presented herein. Based on previous research, it is expected and indeed observed that the k-ω model has a tendency to underpredict resistance [31]. More sophisticated modelling approaches, such as those accounting for transition or those resolving large parts of the turbulent kinetic energy spectrum, should be used to assess the sensitivity of the adopted approach to turbulence modelling.…”

“…To account for turbulence within the fluid, the k-ω model of Wilcox [30] is used. This choice is made following previous work, which showed the particular model to be stable and provide the fastest solution time of all two-equation variants [31]. Benefits of using the k-ω model include its seamless application to low y + type meshes (y + < 1).…”