Influence of the Drag Force on the Average Absorbed Power of Heaving Wave Energy Converters Using Smoothed Particle Hydrodynamics

Abstract

In this paper, we investigated how the added mass, the hydrodynamic damping and the drag coefficient of a Wave Energy Converter (WEC) can be calculated using DualSPHysics. DualSPHysics is a software application that applies the Smoothed Particle Hydrodynamics (SPH) method, a Lagrangian meshless method used in a growing range of applications within the field of Computational Fluid Dynamics (CFD). Furthermore, the effect of the drag force on the WEC’s motion and average absorbed power is analyzed. Particularly under controlled conditions and in the resonance region, the drag force becomes significant and can greatly reduce the average absorbed power of a heaving point absorber. Once the drag coefficient has been determined, it is used in a modified equation of motion in the frequency domain, taking into account the effect of the drag force. Three different methods were compared for the calculation of the average absorbed power: linear potential flow theory, linear potential flow theory modified to take the drag force into account and DualSPHysics. This comparison showed the considerable effect of the drag force in the resonance region. Calculations of the drag coefficient were carried out for three point absorber WECs: one spherical WEC and two cylindrical WECs. Simulations in regular waves were performed for one cylindrical WEC with two different power take-off (PTO) systems: a linear damping and a Coulomb damping PTO system. The Coulomb damping PTO system was added in the numerical coupling between DualSPHysics and Project Chrono. Furthermore, we considered the optimal PTO system damping coefficient taking the effect of the drag force into account.

Towards a High Order Convergent ALE-SPH Scheme with Efficient WENO Spatial Reconstruction

“…Since then, SPH has been used in a large number of applications that range from environmental and coastal engineering to energy production [4]. Nowadays, SPH is widely used for Computational Fluid Dynamics [5,6] and applied to a number of problems in hydraulics, including wastewater works [7], turbine design [8], fish passage flows [9], interaction of free-surface flows with flexible structures [10], sloshing in partially filled tanks [11], analysis of Wave Energy Converters (WEC) [12], study of the impact of sea waves on structures [13], and Large Eddy Simulation (LES) modelling of turbulent flows for moderate [14] and, more recently, high [15] Reynolds numbers. For geometrically complex problems and/or multiphysics applications for which the creation of computational grids is a practical burden, SPH already represents a real alternative to more established mesh-based tools.…”

A Numerical Validation of 3D Experimental Dam-Break Wave Interaction with a Sharp Obstacle Using DualSPHysics

“…DualSPHysics [25] is an advanced meshless solver with emphasis on free-surface flow modeling and has been shown to be robust and accurate in a wide range of applications: reproducing extreme wave events [26], coastal engineering simulations [27,28], fluid-solid interaction (FSI) [29,30], wave energy converters [31][32][33][34][35], etc. The peculiarities of this solver make it suitable for dam-break simulations, since it is naturally able to handle large deformations and violent impacts that involve solid obstacles [36,37]; it follows that SPH-based numerical models could be as effective as, if not better than, the traditional methods applied to the dam failure records, such as the ones based on 2D SWEs [38,39] or the VOF-or FEM-based [40,41] models.…”

On the Development of a Novel Approach for Simulating Elastic Beams in Dualsphysics With the Use of the Project Chrono Library

“…The DualSPHysics code has been applied to several multiphysics phenomena, for example in coastal engineering simulations: to compute forces exerted by large waves on the urban furniture of a realistic promenade [2], to study the run-up on a real armour block coastal breakwater [3,4] and to simulate large waves generated by land-slide events [5]. Other successful applications of DualSPHysics are performed in the field of renewable energies, for example the simulation of Wave Energy Converters (WECs) in several contexts: from the study of the moorings and floatings dynamics [6,7,8,9], to the efficiency [10] and survivability [11] analysis when combined with closed loops [12,13], PTO systems [4,14] or non linear mechanical constraints [15]. These works present first attempts of reproducing the effects of power take-off systems through simplified, although reliable, approaches.…”