Hydrodynamics of planing hulls is affected by proximity to the seabed floor in shallow waters.In this study,a three-dimensional steady linearized model based on the potential theory is applied to model flat planing su...Hydrodynamics of planing hulls is affected by proximity to the seabed floor in shallow waters.In this study,a three-dimensional steady linearized model based on the potential theory is applied to model flat planing surfaces at finite water depth and finite Froude numbers.Modeling results for shallow waters agree with experimental data in the subcritical and supercritical regimes sufficiently far from the critical speed that corresponds to the depth Froude number of unity.At the critical speed,nonlinear and unsteady effects become important,and a different modeling approach is required.展开更多
Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μthe damping coefficient and V the local averaging flow velocity)are employed in this work to investigate the phenomenon o...Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μthe damping coefficient and V the local averaging flow velocity)are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water waves.The numerical results are compared with experimental data available in the literature.The comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the resonant frequency reasonably well.However the conventional potential flow model(without artificial damping term)significantly over-predicts the wave height in narrow gaps around the resonant frequency.In order to calibrate the appropriate damping coefficient used for the potential model and make it work as well as the viscous fluid model in predicting the resonant wave height in narrow gaps but with little computational efforts,the dependence of damping coefficientμon the body geometric dimensions is examined considering the parameters of gap width Bg,body draft D,body breadth ratio Br and body number n(n=2,3),where Br=BB/BA for the case of two bodies(Body A and Body B)with different breadths of BA and BB,respectively.It was confirmed that the damping coefficient used for the potential flow model is not sensitive to the geometric dimensions and spatial arrangement.It was found thatμ∈[0.4,0.5]may guarantee the variation of Hg/H0 with kh to be generally in good agreement with the experimental data and the results of viscous fluid model,where Hg is the excited wave height in narrow gaps under various dimensionless incident wave frequencies kh,H0 is the incident wave height,k=2π/L is the wave number and h is the water depth.展开更多
文摘Hydrodynamics of planing hulls is affected by proximity to the seabed floor in shallow waters.In this study,a three-dimensional steady linearized model based on the potential theory is applied to model flat planing surfaces at finite water depth and finite Froude numbers.Modeling results for shallow waters agree with experimental data in the subcritical and supercritical regimes sufficiently far from the critical speed that corresponds to the depth Froude number of unity.At the critical speed,nonlinear and unsteady effects become important,and a different modeling approach is required.
基金supports from the Natural National Science Foundation of China(Grant Nos.50909016,50921001 and 10802014)support of ARC Discovery Project Program(Grant No.DP0557060)supported by the Open Fund from the State Key Laboratory of Structural Analysis for Industrial Equipment(Grant No.GZ0909)
文摘Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μthe damping coefficient and V the local averaging flow velocity)are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water waves.The numerical results are compared with experimental data available in the literature.The comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the resonant frequency reasonably well.However the conventional potential flow model(without artificial damping term)significantly over-predicts the wave height in narrow gaps around the resonant frequency.In order to calibrate the appropriate damping coefficient used for the potential model and make it work as well as the viscous fluid model in predicting the resonant wave height in narrow gaps but with little computational efforts,the dependence of damping coefficientμon the body geometric dimensions is examined considering the parameters of gap width Bg,body draft D,body breadth ratio Br and body number n(n=2,3),where Br=BB/BA for the case of two bodies(Body A and Body B)with different breadths of BA and BB,respectively.It was confirmed that the damping coefficient used for the potential flow model is not sensitive to the geometric dimensions and spatial arrangement.It was found thatμ∈[0.4,0.5]may guarantee the variation of Hg/H0 with kh to be generally in good agreement with the experimental data and the results of viscous fluid model,where Hg is the excited wave height in narrow gaps under various dimensionless incident wave frequencies kh,H0 is the incident wave height,k=2π/L is the wave number and h is the water depth.
