Abstract
Reviewing the literature of CFD-based numerical wave tanks for wave energy applications, it can be observed that different flow conditions and different turbulence models are applied during numerical wave energy converter (WEC) experiments. No single turbulence model can be identified as an `industry standard’ for WEC modeling. The complexity of the flow field around a WEC, together with the strong dependency of turbulence effects on the shape, operational conditions, and external forces, hampers the formulation of such an `industry standard’. Furthermore, the conceptually different flow characteristics (i.e., oscillating, free surface flows), compared to the design cases of most turbulence models (i.e., continuous single-phase flow), can be identified as a source for the potential lack of accuracy of turbulence models for WEC applications. This communication performs a first step towards analyzing the accuracy and necessity of modeling turbulence effects, by means of turbulence models, within CFD-based NWTs for WEC applications. To that end, the influence of turbulence models and, in addition, the influence of the initial turbulence intensity is investigated based on different wave–structure interaction cases considering two separately validated WEC models. The results highlight the complexity of such a `turbulence analysis’ and the study suggests specific future work to get a better understanding of the model requirements for the flow field around WECs.
Highlights
Received: 29 October 2020 Accepted: 18 December 2020 Published: 23 December 2020Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Copyright: c 2020 by the authors
Given that any physical dissipation due to the mere presence of fluid viscosity would be captured in the viscous laminar case, together with the findings in [50,51], the behavior of the turbulent test cases indicates that turbulence modeling in the considered wave-only case induces artificial numerical dissipation, which should be avoided
It can be stated that the use of turbulence models has a significant influence on the modeled free surface elevation, the wave excitation forces, and the device dynamics
Summary
Received: 29 October 2020 Accepted: 18 December 2020 Published: 23 December 2020Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Copyright: c 2020 by the authors. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The economic viability is commonly expressed by a single, monetary value: the levelized cost of energy (LCoE). From a hydrodynamic point of view, to drive down the LCoE, optimization of the hydrodynamic response of the device is required, which can be achieved through optimization of the shape, the operational degrees of freedom (DoFs), or implementation of energy maximizing control systems (EMCSs). For the hydrodynamic optimization and the synthesis and evaluation of EMCSs at low to mid technology readiness levels (TRLs) [2], researchers and developers rely on complementary experimental and numerical analysis, allowing experimentation in relatively controlled environments, compared to open ocean trials
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