Comparison of wave–structure interaction dynamics of a submerged cylindrical point absorber with three degrees of freedom using potential flow and computational fluid dynamics models
Comparison of wave–structure interaction dynamics of a submerged cylindrical point absorber with three degrees of freedom using potential flow and computational fluid dynamics models
复制标题
DOI：
10.1063/5.0022401
复制
发表时间：
2020-09
影响因子：
4.6
通讯作者：
Panagiotis Dafnakis;A. Bhalla;S. Sirigu;M. Bonfanti;G. Bracco;G. Mattiazzo
中科院分区：
文献类型：
--
作者：
Panagiotis Dafnakis;A. Bhalla;S. Sirigu;M. Bonfanti;G. Bracco;G. Mattiazzo
在本文中，我们比较了垂荡，浪涌和俯仰动力学的淹没圆柱形点吸收器，模拟使用势流和完全解决计算流体动力学（CFD）模型。势流模型基于时域康明斯方程，而CFD模型使用虚拟域Brinkman惩罚技术。使用动力输出（PTO）装置将水下圆柱体拴在海床上，动力输出装置可抑制转换器的升沉、纵荡和纵摇运动，并吸收所有三种模式的能量。它表明，潜在的理论overpredicts升沉和浪涌运动的振幅，而它的结果在一个完全淹没的轴对称转换器的一个微不足道的俯仰。它还低估了浮标的缓慢漂移，CFD模型能够可靠地捕获。此外，我们使用完全解决的CFD模拟研究的三个自由度的圆柱形浮标的性能在不同的PTO系数，质量密度的浮标，和传入波高。它表明，PTO系数预测的线性势理论是次优的波的中度和高陡度。当选择比PTO阻尼的预测值高的值时，波吸收效率显著提高。不同质量密度的浮标的模拟表明，低质量密度的转换器在其PTO和系泊缆中具有增加的张力。此外，质量密度也影响装置的共振周期的范围。最后，不同波高的模拟表明，在较高的高度，波的转换器的吸收效率降低，大部分可用的波能保持未被吸收。
In this paper, we compare the heave, surge, and pitch dynamics of a submerged cylindrical point absorber, simulated using potential flow and fully resolved computational fluid dynamics (CFD) models. The potential flow model is based on the time-domain Cummins equation, whereas the CFD model uses the fictitious domain Brinkman penalization technique. The submerged cylinder is tethered to the seabed using a power take-off (PTO) unit, which restrains the heave, surge, and pitch motions of the converter and absorbs energy from all three modes. It is demonstrated that the potential theory overpredicts the amplitudes of heave and surge motions, whereas it results in an insignificant pitch for a fully submerged axisymmetric converter. It also underestimates the slow drift of the buoy, which the CFD model is able to capture reliably. Furthermore, we use fully resolved CFD simulations to study the performance of a three degrees of freedom cylindrical buoy under varying PTO coefficients, mass density of the buoy, and incoming wave heights. It is demonstrated that the PTO coefficients predicted by the linear potential theory are sub-optimal for waves of moderate and high steepness. The wave absorption efficiency improves significantly when a value higher than the predicted value of the PTO damping is selected. Simulations with different mass densities of the buoy show that converters with low mass densities have an increased tension in their PTO and mooring lines. Moreover, the mass density also influences the range of resonance periods of the device. Finally, simulations with different wave heights show that at higher heights, the wave absorption efficiency of the converter decreases and a large portion of available wave power remains unabsorbed.