Numerical study of fixed Oscillating Water Column with RANS-type two-phase CFD model

Abstract

Various studies investigated the behaviour and the performance of Oscillating Water Columns (OWCs) suggesting many alternative design concepts to improve the efficiency of the device. The OWCs examined here are fixed on the seabed and have a slit opening at the seaward side. The present study investigates the applicability of a multiphase Reynolds Averaged Navier-Stokes (RANS) numerical model for simulating the interaction between an OWC and regular and irregular waves. An initial validation of the open-source computational fluid dynamics (CFD) software package OpenFOAM with the wave generation and absorption toolbox waves2Foam is performed against experimental results obtained at the COAST laboratory of the University of Plymouth. The main aim of the study is to complement to the validation of RANS CFD models and later employ the broadly used numerical tool for further studies for better understanding the behaviour of the OWCs. A method based on mechanical damped oscillations for calculating the eigenfrequency of the device from a decay test is presented and compared with the performance curve. The strength of CFD modelling for obtaining better insight to the hydrodynamics of OWCs is also demonstrated.

High-fidelity numerical modelling of ocean wave energy systems: A review of computational fluid dynamics-based numerical wave tanks

“…Type DOF Array Description [15,17,122,123,202] g P -Flap-type OWSC [176] s P -WaveRoller [68,69,85,86,90,91,97,103,116,152,158,169,184,180,216,224] [18,22,24,33,34,38,41,45,48,51,61,63,64,73,76,88,106,107,118,130,140,141,144,159,167,186,222] g --fixed at far field boundary (FFB) [50,59,70,…”

“…(i) Providing no information and simply defining the discretisation as converged (ii) Qualitative assessment by visual inspection of graphs (iii) Quantitative assessment via the relative change of a certain quantity between the discretisation levels Categories (i) and (ii) are the most common. Only studies [31,92,113,211,222] provides a quantified convergence assessment, stating difference between tested meshes of 0.5% to 12%. However, considering [200,201], certainty about grid convergences can not necessarily be assumed.…”

“…Fixed time step CFL condition [15,17,[22][23][24]33,41,50,51,53,63,58,66,75,95,108,134,160,162,166,167,178,[193][194][195][196][197][198][199]211] [122], chap.5, [99,165,186,191,192,209,206,207,212,213,222] between experimental results and numerical simulations are found for LES than the − k ω SST model, at a higher computational price.…”

“…The − k ε model has mainly been applied for the simulation of OWCs [18,22,24,33,38,41,51,63,64,76,79,93,96,104,[106][107][108]118,159,186,222]. The application in the different studies range from performance analysis [18,118,159,222], (structural) optimisation [76,186], to SI [96]. However, none of the studies disclose a reasoning for their choice of turbulence model.…”

Wave Power Extraction from a Dual Oscillating-Water- Column System Composed of Heave-Only and Onshore Units

“…Comprehensive studies have been carried out to investigate and optimize OWC devices from the perspectives of analytical analysis [6][7][8], numerical simulation [9][10][11], and physical experiment [12][13][14] in the literature. The majority of these works have more concentrated on the single OWC device and optimizing the device geometric parameters to achieve its highly-efficient hydrodynamic performance.…”