Nonlinear loading of a two-dimensional heaving box

Rodriguez, Marcos; Spinneken, Johannes; Swan, Chris

doi:10.1016/j.jfluidstructs.2015.11.001

Cited by 8 publications

(2 citation statements)

References 27 publications

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“…Drag forces are also commonly included in parametrised form as in the Morison equation [15], but this requires calibration of drag coefficients. Such calibration is then made via experiments (see e.g., Rodriguez and Spinnekens work on a heaving box [16,17]) or via CFD simulations (as in the viscous correction method of Bhinder et al [18]). The work of Stansby et al [19] and Gu et al [20] present RANS simulations of different cylinder bottom geometries in surge and heave decay.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Palm

Eskilsson

Bergdahl

et al. 2018

JMSE

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This paper analyses the nonlinear forces on a moored point-absorbing wave energy converter (WEC) in resonance at prototype scale (1:1) and at model scale (1:16). Three simulation types were used: Reynolds Averaged Navier-Stokes (RANS), Euler and the linear radiation-diffraction method (linear). Results show that when the wave steepness is doubled, the response reduction is: (i) 3% due to the nonlinear mooring response and the Froude-Krylov force; (ii) 1-4% due to viscous forces; and (iii) 18-19% due to induced drag and non-linear added mass and radiation forces. The effect of the induced drag is shown to be largely scale-independent. It is caused by local pressure variations due to vortex generation below the body, which reduce the total pressure force on the hull. Euler simulations are shown to be scale-independent and the scale effects of the WEC are limited by the purely viscous contribution (1-4%) for the two waves studied. We recommend that experimental model scale test campaigns of WECs should be accompanied by RANS simulations, and the analysis complemented by scale-independent Euler simulations to quantify the scale-dependent part of the nonlinear effects.

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Section: Introductionmentioning

confidence: 99%

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Palm

Eskilsson

Bergdahl

et al. 2018

JMSE

View full text Add to dashboard Cite

show abstract

“…Mohapatra and Guedes Soares [28] studied the wave forces on a two-dimensional rectangular floating structure based on linearized Boussinesq. Rodriguez et al [29] investigated the numerical nonlinear heave response of a rectangular box concerning the importance of the relative body dimensions. Islam et al [30] analyzed the wave radiation of a heaving box-type floating structure based on CFD simulations with a volume of fluid method.…”

Section: Introductionmentioning

confidence: 99%

Energy Efficiency Analysis of Multi-Type Floating Bodies for a Novel Heaving Point Absorber with Application to Low-Power Unmanned Ocean Device

et al. 2018

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Long-term energy supplies hinder the application of the low-power unmanned ocean devices to the deep sea. Ocean wave energy is a renewable resource with amount stores of enormous and high density. The wave energy converter (WEC) could be miniaturized so that it can be integrated into the devices to make up the power module. In this paper, a small novel heaving point absorber of energy supply for low-power unmanned ocean devices is developed based on the counter-rotating self-adaptive mechanism. The floating body as an important part of the heaving point absorber, the geometric parameters is optimized to increase the efficiency of power production. Through constructing the constitutive relation between the geometric parameters, the wave force, the motion displacement, the motion velocity, and the capture width ratio of the floating body, the energy efficiency characteristics of the multi-type floating bodies are calculated, and the optimal shape is selected. On the other hand, in the calculation process of the wave force, the Froude-Krylov method is an effective method to accurately calculate the wave excitation force. Meanwhile, nonlinear static and dynamic Froude-Krylov force effectively overcomes the inaccuracy of the linear models and reduces the time consumed to simulate. Finally, the wave force, heaving velocity, heaving displacement, and capture width ratio of the three floating bodies are compared and analyzed, and the results show that the cylindrical floater that is vertically placed on the wave surface is more suitable for the novel heaving wave energy point absorber.

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A laboratory study on the loading and motion of a heaving box

Rodriguez

Spinneken

2016

Journal of Fluids and Structures

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This paper concerns the nonlinear loading and dynamic response of a heaving rectangular box in two dimensions, using a series of experimental tests in regular and irregular wave conditions. Nonlinear forcing components are found to make major contributions to both the excitation problem and the motion response. Two main sources of nonlinearity are established: the first associated with higher-order wave–structure interactions, and the second associated with viscous dissipation. The present work quantifies the relative influence of these two sources. Adopting a series of regular wave cases, the first source, prevalent in steep wave conditions, is shown to be particularly significant in the diffraction regime, leading to significant excitation force amplifications. In deep water, these nonlinearities are primarily driven by interactions between incident and reflected wave components. The second source, due to vortex shedding, plays a minor role in the excitation problem, but has a major influence on the motion response. Vortex-induced effects are particularly important when the structure exhibits large motions, for example at resonance. To characterise the response in irregular waves, experimental data are provided comprising in excess of 100,000 individual waves, presenting one of the most substantial data sets of this kind to date. In considering these irregular sea states, the two aforementioned sources of nonlinearity are again found to be of critical importance. While wave-induced load amplifications of up to 60% may be observed in the excitation problem, the motion response is primarily governed by vortex-induced attenuations. In order to provide practical engineering solutions, two approaches are offered. For nonlinear forcing predictions, a two parameter Weibull fit is found to be both simple and accurate. In terms of the heave motion, a computationally efficient time-domain simulation, building upon a linear hydrodynamic description and a quadratic MOJS type drag term, leads to good agreement with experimental data

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Nonlinear loading of a two-dimensional heaving box

Cited by 8 publications

References 27 publications

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Energy Efficiency Analysis of Multi-Type Floating Bodies for a Novel Heaving Point Absorber with Application to Low-Power Unmanned Ocean Device

A laboratory study on the loading and motion of a heaving box

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