Nonlinear wave-body interactions for a stationary surface-piercing body in water of finite depth with fiat and sloping bottoms are simulated in a two-dimensional numerical wave tank, which is constructed mainly based ...Nonlinear wave-body interactions for a stationary surface-piercing body in water of finite depth with fiat and sloping bottoms are simulated in a two-dimensional numerical wave tank, which is constructed mainly based on the spatially averaged Navier-Stokes equations with the k- ε model for simulating the turbulence. The equations are discretized based on the finite volume method and the scheme of the pressure implicit splitting of operators is employed to solve the Navier-Stokes equations. By using the force time histories, the mean and higher-harmonic force components are calculated. The computational results are shown to be in good agreement with experimental and numerical results of other researchers. Then, the horizontal force, the vertical force and the moment on the surface-piercing body under nonlinear regular waves with flat and sloping bottoms are obtained. The results indicate that the bottom topographies have a significant influence on the wave loads on the surface-piercing body.展开更多
For computation of large amplitude motions of ships fastened to a dock, a fast evaluation scheme is implemented for computation of the time-domain Green function for finite water depth. Based on accurate evaluation of...For computation of large amplitude motions of ships fastened to a dock, a fast evaluation scheme is implemented for computation of the time-domain Green function for finite water depth. Based on accurate evaluation of the Green function directly, a fast approximation method for the Green function is developed by use of Chebyshev polynomials. Examinations are carried out of the accuracy of the Green function and its derivatives from the scheme. It is shown that when an appropriate number of polynomial terms are used, very accurate approximation can be obtained.展开更多
Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non-desingularized technique.Free surface and seabed surface profiles are represented by continuous panels rather th...Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non-desingularized technique.Free surface and seabed surface profiles are represented by continuous panels rather than a discretization by isolated points.These panels are positioned exactly on the fluid boundary surfaces and therefore no desingularization technique is required.Space increment method is applied for both free surface source and seabed source arrangements to reduce computational cost and improve numerical efficiency.Fourth order Runge-Kutta iteration scheme is adopted on the free surface updating at every time step.The finite water depth effect is studied quantitatively for a series of cylinders with different B/T ratios.The accuracy and efficiency of the proposed model are validated by comparison with published numerical results and experimental data.Numerical results show that hydrodynamic coefficients vary for cylinder bodies with different ratios of B/T.For certain set of B/T ratios the effect of finite water depth increases quickly with the increase of motion frequency and becomes stable when frequency is relatively large.It also shows that water depths have larger hydrodynamic effects on cylinder with larger breadth to draft ratios.Both the heave added mass and damping coefficients increase across the frequency range with the water depths decrease for forced heave motion.The water depths have smaller effects on sway motion response than on heave motion response.展开更多
A nonlinear short-crested wave system, consisting of two progressive waves propagating at an oblique angle to each other in a fluid of finite depth, is investigated by means of an analytical approach named the homotop...A nonlinear short-crested wave system, consisting of two progressive waves propagating at an oblique angle to each other in a fluid of finite depth, is investigated by means of an analytical approach named the homotopy analysis method （HAM）. Highly convergent series solutions are explicitly derived for the velocity potential and the surface wave elevation. We find that, at every value of water depth, there is little difference between the kinetic energy and the potential energy for nonlinear waves. The nonlinear short-crested waves with a larger angle of incidence always contain the more potential wave energy. With the aid of the HAM, we obtain the dispersion relation for nonlinear short-crested waves. Furthermore, it is shown that the wave elevation tends to be smoothened at the crest and be sharpened at the trough as the water depth increases, and the wave pressure crests and troughs become steeper with increasing incident wave steepness.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 40776057)the Knowledge Innovation Program of Chinese Academy of Sciences (Grant Nos. KJCX2-YW-L07,KZCX2-YW-212-2)
文摘Nonlinear wave-body interactions for a stationary surface-piercing body in water of finite depth with fiat and sloping bottoms are simulated in a two-dimensional numerical wave tank, which is constructed mainly based on the spatially averaged Navier-Stokes equations with the k- ε model for simulating the turbulence. The equations are discretized based on the finite volume method and the scheme of the pressure implicit splitting of operators is employed to solve the Navier-Stokes equations. By using the force time histories, the mean and higher-harmonic force components are calculated. The computational results are shown to be in good agreement with experimental and numerical results of other researchers. Then, the horizontal force, the vertical force and the moment on the surface-piercing body under nonlinear regular waves with flat and sloping bottoms are obtained. The results indicate that the bottom topographies have a significant influence on the wave loads on the surface-piercing body.
文摘For computation of large amplitude motions of ships fastened to a dock, a fast evaluation scheme is implemented for computation of the time-domain Green function for finite water depth. Based on accurate evaluation of the Green function directly, a fast approximation method for the Green function is developed by use of Chebyshev polynomials. Examinations are carried out of the accuracy of the Green function and its derivatives from the scheme. It is shown that when an appropriate number of polynomial terms are used, very accurate approximation can be obtained.
基金the support by the National Natural Science Foundation of China(No.11372184)
文摘Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non-desingularized technique.Free surface and seabed surface profiles are represented by continuous panels rather than a discretization by isolated points.These panels are positioned exactly on the fluid boundary surfaces and therefore no desingularization technique is required.Space increment method is applied for both free surface source and seabed source arrangements to reduce computational cost and improve numerical efficiency.Fourth order Runge-Kutta iteration scheme is adopted on the free surface updating at every time step.The finite water depth effect is studied quantitatively for a series of cylinders with different B/T ratios.The accuracy and efficiency of the proposed model are validated by comparison with published numerical results and experimental data.Numerical results show that hydrodynamic coefficients vary for cylinder bodies with different ratios of B/T.For certain set of B/T ratios the effect of finite water depth increases quickly with the increase of motion frequency and becomes stable when frequency is relatively large.It also shows that water depths have larger hydrodynamic effects on cylinder with larger breadth to draft ratios.Both the heave added mass and damping coefficients increase across the frequency range with the water depths decrease for forced heave motion.The water depths have smaller effects on sway motion response than on heave motion response.
基金Supported by the National Key Basic Research Development Program of China(973 Program,Grant No.2014CB046203)the National Natural Science Foundation of China(Grant No.11472166)the Natural Science Founda-tion of Shanghai(Grant No.14ZR1416200)
文摘A nonlinear short-crested wave system, consisting of two progressive waves propagating at an oblique angle to each other in a fluid of finite depth, is investigated by means of an analytical approach named the homotopy analysis method （HAM）. Highly convergent series solutions are explicitly derived for the velocity potential and the surface wave elevation. We find that, at every value of water depth, there is little difference between the kinetic energy and the potential energy for nonlinear waves. The nonlinear short-crested waves with a larger angle of incidence always contain the more potential wave energy. With the aid of the HAM, we obtain the dispersion relation for nonlinear short-crested waves. Furthermore, it is shown that the wave elevation tends to be smoothened at the crest and be sharpened at the trough as the water depth increases, and the wave pressure crests and troughs become steeper with increasing incident wave steepness.
