The fluid viscosity is known to have a significant effect on the hydrodynamic characteristics which are linked to the power conversion ability of the wave energy converter(WEC). To overcome the disadvantages of case-b...The fluid viscosity is known to have a significant effect on the hydrodynamic characteristics which are linked to the power conversion ability of the wave energy converter(WEC). To overcome the disadvantages of case-by-case study through the experiments and numerical computations employed by the former researches, the viscous effect is studied comprehensively for multiple geometries in the present paper. The viscous effect is expressed as the viscous added mass and damping solved by the free-decay method. The computational fluid dynamics(CFD) method is employed for the calculation of the motion and flow field around the floater. The diameter to draft ratio and bottom shape are considered for the geometrical evaluation on the viscous effect. The results show that a slenderer floater presents a stronger viscous effect. Through the comparisons of the floaters with four different bottom shapes, the conical bottom is recommended in terms of low viscous effect and simple geometry for manufacture. A viscous correction formula for a series of cylindrical floaters is put forward, for the first time, to help the engineering design of outer-floaters of point-absorber WECs.展开更多
Based on the field velocity method,a novel approach for simulating unsteady pitching and plunging motion of an airfoil is presented in this paper.Responses to pitching and plunging motions of the airfoil are simulated...Based on the field velocity method,a novel approach for simulating unsteady pitching and plunging motion of an airfoil is presented in this paper.Responses to pitching and plunging motions of the airfoil are simulated under different conditions.The obtained results are compared with those of moving grid method and good agreement is achieved.In the conventional field velocity method,the Euler solver is usually used to simulate the movement of the airfoil.However,when viscous effect is considered,unsteady Navier-Stokes equations have to be solved and the viscous flux correction must be taken into account.In this work,the viscous flux correction is introduced into the conventional field velocity method when non-uniform grid speed distribution is occurred.Numerical experiments for the flow around NACA0012 airfoil showed that the proposed approach can well simulate viscous moving boundary flow problems.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51761135013)the High Technology Ship Scientific Research Project from Ministry of Industry and Information Technology of the People’s Republic of China–Floating Security Platform Project(the second stage,201622)+1 种基金the Fundamental Research Fund for the Central University(Grant Nos.HEUCF180104 and HEUCFP201809)the China Scholarship Council(the International Clean Energy Talent Program,2017)
文摘The fluid viscosity is known to have a significant effect on the hydrodynamic characteristics which are linked to the power conversion ability of the wave energy converter(WEC). To overcome the disadvantages of case-by-case study through the experiments and numerical computations employed by the former researches, the viscous effect is studied comprehensively for multiple geometries in the present paper. The viscous effect is expressed as the viscous added mass and damping solved by the free-decay method. The computational fluid dynamics(CFD) method is employed for the calculation of the motion and flow field around the floater. The diameter to draft ratio and bottom shape are considered for the geometrical evaluation on the viscous effect. The results show that a slenderer floater presents a stronger viscous effect. Through the comparisons of the floaters with four different bottom shapes, the conical bottom is recommended in terms of low viscous effect and simple geometry for manufacture. A viscous correction formula for a series of cylindrical floaters is put forward, for the first time, to help the engineering design of outer-floaters of point-absorber WECs.
基金This work was supported by The National Basic Research Program of China(Grant No.2007CB714600)Funding of Jiangsu Innovation Program for Graduate Education(Grant No.CXLX110170).
文摘Based on the field velocity method,a novel approach for simulating unsteady pitching and plunging motion of an airfoil is presented in this paper.Responses to pitching and plunging motions of the airfoil are simulated under different conditions.The obtained results are compared with those of moving grid method and good agreement is achieved.In the conventional field velocity method,the Euler solver is usually used to simulate the movement of the airfoil.However,when viscous effect is considered,unsteady Navier-Stokes equations have to be solved and the viscous flux correction must be taken into account.In this work,the viscous flux correction is introduced into the conventional field velocity method when non-uniform grid speed distribution is occurred.Numerical experiments for the flow around NACA0012 airfoil showed that the proposed approach can well simulate viscous moving boundary flow problems.
