Based on the linear wave theory, the lift force on the cylinder under the action of both regular waves and currents related to inline force and the resultant force has been investigated. The relationship between the h...Based on the linear wave theory, the lift force on the cylinder under the action of both regular waves and currents related to inline force and the resultant force has been investigated. The relationship between the hydrodynamic coefficients of resultant force Cf, of drag force Cd, of inertia force Cm and of lift force CL and the redefined KC number is reported. It is indicated that in a certain region of KC number, the influence of lift force on the resultant force can not be ignored.展开更多
The in-line response of a vertical flexibly mounted cylinder in regular and random waves is reported. Both theoretical analyses and experimental measurements have been performed. The theoretical predictions are based ...The in-line response of a vertical flexibly mounted cylinder in regular and random waves is reported. Both theoretical analyses and experimental measurements have been performed. The theoretical predictions are based on the Morison equation which is solved by the incremental harmonic balance method. Experiments are then performed in a wave flume to determine the accuracy of the Morison equation in predicting the in-line response of the cylinder in regular and random waves. The interaction between waves and vibrating cylinders are investigated.展开更多
The interaction of water waves with multiple circular cylinders is analysed briefly in this paper. The formula obtained by Linton and Evans is improved to introduce a relation of phase between cylinders. The condition...The interaction of water waves with multiple circular cylinders is analysed briefly in this paper. The formula obtained by Linton and Evans is improved to introduce a relation of phase between cylinders. The condition for the existence of the solution has been proved. The numerical results are compared with analytic solutions (Linton and Evans), numerical solutions and experimental data (Isaacson), and good agreement has been found.展开更多
In this study, we examine the water wave radiation by arrays of truncated circular cylinders. Each cylinder can oscillate independently in any rigid oscillation mode with a prescribed amplitude, including translationa...In this study, we examine the water wave radiation by arrays of truncated circular cylinders. Each cylinder can oscillate independently in any rigid oscillation mode with a prescribed amplitude, including translational and rotational modes such as surge, sway, heave, pitch, roll, and their combinations. Based on the eigenfunction expansion and Graf's addition theorem for Bessel functions, we developed an analytical method that includes the effects of evanescent modes in order to analyze such arrays of cylinders. To investigate the effects of several influential factors on convergence,our objective is to dramatically reduce the number of tests required and determine the influencing relationships between truncation number and convergence behavior for different factor combinations. We use the orthogonal test method to fulfill the objective. Lastly, we present our results regarding the effects of evanescent modes on hydrodynamic coefficients.展开更多
The present study theoretically as well as experimentally investigates the interaction between waves and an array of porous circular cylinders with or without an inner porous plate based on the linear wave theory. To ...The present study theoretically as well as experimentally investigates the interaction between waves and an array of porous circular cylinders with or without an inner porous plate based on the linear wave theory. To design more effective floating breakwaters, the transmission rate of waves propagating through the array is evaluated. Each cylinder in the array is partly made of porous materials. Specifically, it possesses a porous sidewall and an impermeable bottom. In addition, an inner porous plate is horizontally fixed inside the cylinders. It dissipates the wave more effectively and eliminates the sloshing phenomenon. The approach suggested by Kagemoto and Yue (1986) is adopted to solve the multiple-scatter problem, while a hierarchical interaction theory is adopted to deal with hydrodynamic interactions among a great number of bodies, which efficiently saves computation time. Meanwhile, a series of model tests with an array of porous cylinders is performed in a wave basin to validate the theoretical work and the calculated results. The draft of the cylinders, the location of the inner porous plate, and the spacing between adjacent cylinders are also adjusted to investigate their effects on wave dissipation.展开更多
A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary...A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary waves are produced by means of gravitational collapse at the layer thickness ratio of 0.2, and the internal periodic waves are produced with rocker-flap wave maker at the layer thickness ratio of 0.93. The wave parameters are obtained through dyeing photography. The vertical cylinders of the same size are arranged in different depths. The horizontal force on each cylinder is measured and the vertical distribution rules are researched. The internal wave heights are changed to study the impact of wave heights on the force. The results show that the horizontal force of concave type internal solitary wave on vertical cylinder in the upper-layer fluid has the same direction as the wave propagating, while it has an opposite direction in the lower-layer. The horizontal force is not evenly distributed in the lower fluid. And the force at different depths increases along with wave height. Internal solitary wave can produce an impact load on the entire pile. The horizontal force of internal periodic waves on the vertical cylinders is periodically changed at the frequency of waves. The direction of the force is opposite in the upper and lower layers, and the value is close. In the upper layer except the depth close to the interface, the force is evenly distributed; but it tends to decrease with the deeper depth in the lower layer. A periodic shear load can be produced on the entire pile by internal periodic waves, and it may cause fatigue damage to structures.展开更多
In this paper, a numerical model is established for estimating the wave forces on a submerged horizontal circular cylinder. For predicting the wave motion, a set of two dimensional Navier Stokes equations is solved ...In this paper, a numerical model is established for estimating the wave forces on a submerged horizontal circular cylinder. For predicting the wave motion, a set of two dimensional Navier Stokes equations is solved numerically with a finite element method. In order to track the moving non linear wave surface boundary, the Navier Stokes equations are discretized in a moving mesh system. After each computational time step, the mesh is modified according to the changed wave surface boundary. In order to stabilize the numerical procedure, a three step finite element method is applied in the time integration. The water sloshing in a tank and wave propagation over a submerged bar are simulated for the first time to validate the present model. The computational results agree well with the analytical solution and the experimental data. Finally, the model is applied to the simulation of interaction between waves and a submerged horizontal circular cylinder. The effects of the KC number and the cylinder depth on the wave forces are studied.展开更多
Under the assumption of potential flow and linear wave theory, a semi-analytic method based on eigenfunciton expansion is proposed to predict the hydrody-namic forces on an array of three bottom-mounted, surface-pierc...Under the assumption of potential flow and linear wave theory, a semi-analytic method based on eigenfunciton expansion is proposed to predict the hydrody-namic forces on an array of three bottom-mounted, surface-piercing circular cylinders. The responses of the cylinders induced by wave excitation are determined by the equa-tions of motion coupled with the solutions of the wave radiation and diffraction problems. Experiments for three-cylinder cases are then designed and performed in a wave flume to determine the accuracy of this method for regular waves.展开更多
Large-scale interceptors constitute the main structure of offshore self-driven floating marine litter collection devices,and the structural stability of such interceptors under the action of waves directly influences ...Large-scale interceptors constitute the main structure of offshore self-driven floating marine litter collection devices,and the structural stability of such interceptors under the action of waves directly influences the overall safety of the device.When the ratio of the diameter of a horizontal cylinder in such interceptors to the incident wavelength is larger than 0.25,the wave force can be calculated by using the diffraction theory,by considering the problem as that of the interaction between the waves and a partially immersed large-scale horizontal cylinder.In this study,an analytical approach to calculate the wave force on a partially immersed large-scale horizontal cylinder was formulated by using the stepwise approximation method.Physical model tests were conducted to investigate the effects of different factors(wave height,period,and immersion depth)on the wave force on a large-scale horizontal cylinder under conditions involving short-period waves.The results show that both horizontal and vertical wave forces on the cylinder increase as the wave height(immersion depth)increases in most cases.The vertical wave force decreases with the decrease of the period.For the horizontal wave force,it increases with the decrease of the period when the wavelength is larger than the diameter of the cylinder and decreases with the decrease of the period when the wavelength is smaller than the diameter of the cylinder.展开更多
The selection of wave force models will significantly impact the structural responses of floating wind turbines.In this study,comparisons of wave force model effects on the structural responses and fatigue loads of a ...The selection of wave force models will significantly impact the structural responses of floating wind turbines.In this study,comparisons of wave force model effects on the structural responses and fatigue loads of a semi-submersible floating wind turbine(SFWT)were conducted.Simulations were performed by employing the Morison equation(ME)with linear or second-order wave kinematics and potential flow theory(PFT)with first-or second-order wave forces.A comparison of regular waves,irregular waves,and coupled wind/waves analyses with the experimental data showed that many of the simulation results and experimental data are relatively consistent.However,notable discrepancies are found in the response amplitude operators for platform heave,tower base bending moment,and tension in mooring lines.PFT models give more satisfactory results of heave but more significant discrepan-cies in tower base bending moment than the ME models.In irregular wave analyses,low-frequency resonances were captured by PFT models with second-order difference-frequency terms,and high-frequency resonances were captured by the ME models or PFT models with second-order sum-frequency terms.These force models capture the response frequencies but do not reasonably predict the response amplitudes.The coupled wind/waves analyses showed more satisfactory results than the wave-only analyses.However,an important detail to note is that this satisfactory result is based on the overprediction of wind-induced responses.展开更多
In this paper, we prove the existence of forced waves for Leslie-Gower prey-predator model with nonlocal effects under shifting environment. By constructing a pair of upper and lower solutions with the method of monot...In this paper, we prove the existence of forced waves for Leslie-Gower prey-predator model with nonlocal effects under shifting environment. By constructing a pair of upper and lower solutions with the method of monotone iteration, we can obtain the existence of forced waves for any positive constant shifting speed. Finally, we show the asymptotical behavior of traveling wave fronts in two tails.展开更多
Based on model tests, the lift and resultant forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in this paper. The lift and resultant force coefficients CL and Cf relate...Based on model tests, the lift and resultant forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in this paper. The lift and resultant force coefficients CL and Cf related to KC number and the effect of direction of wave propagation are also given, which may be useful for practical engineering application.展开更多
The total transverse forces on each of the two piles in the side-by-side arrangement and tandem arrangement are experimentally investigated in irregular waves and the total in-line wave forces are measured simultaneou...The total transverse forces on each of the two piles in the side-by-side arrangement and tandem arrangement are experimentally investigated in irregular waves and the total in-line wave forces are measured simultaneously. The statistical and spectral characteristics of the transverse forces are analyzed. The ratio of the transverse force on each pile in group to that on a single pile is defined as the transverse groupling-pile factor, KGL. Both the transverse coefficients CLG and KGL for each pile in array are varied with the relative pile distance and KC number and their relationships are presented in this paper. Also the ratio of the resultant wave froce of in-line force and transverse force to the in-line force and the vriation of the resultant coefficient are investigated.展开更多
The purpose of this study is to develop an analytical formalism and derive series expansions for the time-averaged force and torque exerted on a compound coated compressible liquid-like cylinder,insonified by acoustic...The purpose of this study is to develop an analytical formalism and derive series expansions for the time-averaged force and torque exerted on a compound coated compressible liquid-like cylinder,insonified by acoustic standing waves having an arbitrary angle of incidence in the polar(transverse)plane.The host medium of wave propagation and the eccentric liquid-like cylinder are non-viscous.Numerical computations illustrate the theoretical analysis with particular emphases on the eccentricity of the cylinder,the angle of incidence and the dimensionless size parameters of the inner and coating cylindrical fluid materials.The method to derive the acoustical scattering,and radiation force and torque components conjointly uses modal matching with the addition theorem,which adequately account for the multiple wave interaction effects between the layer and core fluid materials.The results demonstrate that longitudinal and lateral radiation force components arise.Moreover,an axial radiation torque component is quantified and computed for the non-absorptive compound cylinder,arising from geometrical asymmetry considerations as the eccentricity increases.The computational results reveal the emergence of neutral,positive,and negative radiation force and torque depending on the size parameter of the cylinder,the eccentricity,and the angle of incidence of the insonifying field.Moreover,based on the law of energy conservation applied to scattering,numerical verification is accomplished by computing the extinction/scattering energy efficiency.The results may find some related applications in fluid dynamics,particle trapping,mixing and manipulation using acoustical standing waves.展开更多
By using a weakly nonlinear and perturbation method, the generalized inhomogeneous Korteweg de Vries (KdV)- Burgers equation is derived, which governs the evolution of the amplitude of Rossby waves under the influen...By using a weakly nonlinear and perturbation method, the generalized inhomogeneous Korteweg de Vries (KdV)- Burgers equation is derived, which governs the evolution of the amplitude of Rossby waves under the influence of dissipation and slowly varying topography with time. The analysis indicates that dissipation and slowly varying topography with time are important factors in causing variation in the mass and energy of solitary waves.展开更多
During reflection from a solid vertical wall, surface gravity waves produce a steady force on the wall, which was calculated earlier by the momentum method. Recently the linear momentum of these waves has been estimat...During reflection from a solid vertical wall, surface gravity waves produce a steady force on the wall, which was calculated earlier by the momentum method. Recently the linear momentum of these waves has been estimated to be twice as large as deduced from the classical Stokes drift formula. Therefore, the magnitude of the reflected wave force has been doubled here and the algebraic form of the equation is converted to be more understandable physically. Wave force equals fluid density times the square of the particle’s orbital speed and a numerical constant. Observations are welcomed to compare with the theory.展开更多
The hydrodynamic interaction between two vertical cylinders in water waves is investigated based on the linearized potential flow theory. One of the two cylinders is fixed at the bottom while the other is articulated ...The hydrodynamic interaction between two vertical cylinders in water waves is investigated based on the linearized potential flow theory. One of the two cylinders is fixed at the bottom while the other is articulated at the bottom and oscillates with small amplitudes in the direction of the incident wave. Both the diffracted wave and the radiation wave are studied in the present paper. A simple analytical expression for the velocity potential on the surface of each cylinder is obtained by means of Graf's addition theorem. The wave-excited forces and moments on the cylinders, the added masses and the radiation damping coefficients of the oscillating cylinder are all expressed explicitly in series form. The coefficients of the series are determined by solving algebraic equations. Several numerical examples are given to illustrate the effects of various parameters, such as the separation distance, the relative size of the cylinders, and the incident angle, on the first-order and steady second-order forces, the added masses and radiation-damping coefficients as well as the response of the oscillating cylinder.展开更多
The total inline wave forces, the irregular wave forces in particular, on an isolated pile are investigated by experiment. The relationships between force coefficients Cd and CM including in Morison's Eq. . and KC...The total inline wave forces, the irregular wave forces in particular, on an isolated pile are investigated by experiment. The relationships between force coefficients Cd and CM including in Morison's Eq. . and KC number or Reynolds number Re, and the variation of Cd and Cm in frequency domain are analysed with the method of least-squares in time domain and that of cross-spectral analysis. The plots of C4and Cmversus KCare given for both regular and irregular waves and those for irregular waves are used for numerical simulation of the irregular wave forces on the vertical pile and the results are in fairly good agreement with the test data. Based on the experimental results , the applicability of the spectral analysis method for calculating irregular wave forces on an isolated pile is investigated with the coherency γ between wave and wave forces and with KC number.展开更多
-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coeffic...-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.展开更多
文摘Based on the linear wave theory, the lift force on the cylinder under the action of both regular waves and currents related to inline force and the resultant force has been investigated. The relationship between the hydrodynamic coefficients of resultant force Cf, of drag force Cd, of inertia force Cm and of lift force CL and the redefined KC number is reported. It is indicated that in a certain region of KC number, the influence of lift force on the resultant force can not be ignored.
基金The work was supported by the National Natural Science Foundation of China under contract No. 10272118 ;The Hong Kong Polytechnic University Research of China under contract No. A - PE28
文摘The in-line response of a vertical flexibly mounted cylinder in regular and random waves is reported. Both theoretical analyses and experimental measurements have been performed. The theoretical predictions are based on the Morison equation which is solved by the incremental harmonic balance method. Experiments are then performed in a wave flume to determine the accuracy of the Morison equation in predicting the in-line response of the cylinder in regular and random waves. The interaction between waves and vibrating cylinders are investigated.
文摘The interaction of water waves with multiple circular cylinders is analysed briefly in this paper. The formula obtained by Linton and Evans is improved to introduce a relation of phase between cylinders. The condition for the existence of the solution has been proved. The numerical results are compared with analytic solutions (Linton and Evans), numerical solutions and experimental data (Isaacson), and good agreement has been found.
基金supported by the National Natural Science Foundation of China (Grants 11072246, 51490673)the National Basic Research Program (973 Program) of China (Grant 2014CB046801)
文摘In this study, we examine the water wave radiation by arrays of truncated circular cylinders. Each cylinder can oscillate independently in any rigid oscillation mode with a prescribed amplitude, including translational and rotational modes such as surge, sway, heave, pitch, roll, and their combinations. Based on the eigenfunction expansion and Graf's addition theorem for Bessel functions, we developed an analytical method that includes the effects of evanescent modes in order to analyze such arrays of cylinders. To investigate the effects of several influential factors on convergence,our objective is to dramatically reduce the number of tests required and determine the influencing relationships between truncation number and convergence behavior for different factor combinations. We use the orthogonal test method to fulfill the objective. Lastly, we present our results regarding the effects of evanescent modes on hydrodynamic coefficients.
基金supported by the Fundamental Research Funds for the Central Universitiesthe National Natural Science Foundation of China (Grant Nos. 40876049 and 31172446)+1 种基金the Science and Technology Department of Zhejiang Province(Grant No. 2008C12065-1)the Teaching Department of Zhejiang Province (Grant No. Z200803912)
文摘The present study theoretically as well as experimentally investigates the interaction between waves and an array of porous circular cylinders with or without an inner porous plate based on the linear wave theory. To design more effective floating breakwaters, the transmission rate of waves propagating through the array is evaluated. Each cylinder in the array is partly made of porous materials. Specifically, it possesses a porous sidewall and an impermeable bottom. In addition, an inner porous plate is horizontally fixed inside the cylinders. It dissipates the wave more effectively and eliminates the sloshing phenomenon. The approach suggested by Kagemoto and Yue (1986) is adopted to solve the multiple-scatter problem, while a hierarchical interaction theory is adopted to deal with hydrodynamic interactions among a great number of bodies, which efficiently saves computation time. Meanwhile, a series of model tests with an array of porous cylinders is performed in a wave basin to validate the theoretical work and the calculated results. The draft of the cylinders, the location of the inner porous plate, and the spacing between adjacent cylinders are also adjusted to investigate their effects on wave dissipation.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51279187 and 41174157)the Fundamental Research Funds for the Central Universities(Grant No.201262005)the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province(Grant No.BS2013HZ014)
文摘A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary waves are produced by means of gravitational collapse at the layer thickness ratio of 0.2, and the internal periodic waves are produced with rocker-flap wave maker at the layer thickness ratio of 0.93. The wave parameters are obtained through dyeing photography. The vertical cylinders of the same size are arranged in different depths. The horizontal force on each cylinder is measured and the vertical distribution rules are researched. The internal wave heights are changed to study the impact of wave heights on the force. The results show that the horizontal force of concave type internal solitary wave on vertical cylinder in the upper-layer fluid has the same direction as the wave propagating, while it has an opposite direction in the lower-layer. The horizontal force is not evenly distributed in the lower fluid. And the force at different depths increases along with wave height. Internal solitary wave can produce an impact load on the entire pile. The horizontal force of internal periodic waves on the vertical cylinders is periodically changed at the frequency of waves. The direction of the force is opposite in the upper and lower layers, and the value is close. In the upper layer except the depth close to the interface, the force is evenly distributed; but it tends to decrease with the deeper depth in the lower layer. A periodic shear load can be produced on the entire pile by internal periodic waves, and it may cause fatigue damage to structures.
文摘In this paper, a numerical model is established for estimating the wave forces on a submerged horizontal circular cylinder. For predicting the wave motion, a set of two dimensional Navier Stokes equations is solved numerically with a finite element method. In order to track the moving non linear wave surface boundary, the Navier Stokes equations are discretized in a moving mesh system. After each computational time step, the mesh is modified according to the changed wave surface boundary. In order to stabilize the numerical procedure, a three step finite element method is applied in the time integration. The water sloshing in a tank and wave propagation over a submerged bar are simulated for the first time to validate the present model. The computational results agree well with the analytical solution and the experimental data. Finally, the model is applied to the simulation of interaction between waves and a submerged horizontal circular cylinder. The effects of the KC number and the cylinder depth on the wave forces are studied.
基金supported by the National Marine Public Welfare Research Projects of China(No.201005002)The Hong Kong Polytechnic University(No.H-ZG 68)
文摘Under the assumption of potential flow and linear wave theory, a semi-analytic method based on eigenfunciton expansion is proposed to predict the hydrody-namic forces on an array of three bottom-mounted, surface-piercing circular cylinders. The responses of the cylinders induced by wave excitation are determined by the equa-tions of motion coupled with the solutions of the wave radiation and diffraction problems. Experiments for three-cylinder cases are then designed and performed in a wave flume to determine the accuracy of this method for regular waves.
基金This work was financially supported by the Marine Economic Development Subsidy Fund Project in Fujian Province of China(Grant No.FJHJF-L-2019-8)2020 Xiamen Youth Innovation Fund Project of China(Grant No.3502Z20206069).
文摘Large-scale interceptors constitute the main structure of offshore self-driven floating marine litter collection devices,and the structural stability of such interceptors under the action of waves directly influences the overall safety of the device.When the ratio of the diameter of a horizontal cylinder in such interceptors to the incident wavelength is larger than 0.25,the wave force can be calculated by using the diffraction theory,by considering the problem as that of the interaction between the waves and a partially immersed large-scale horizontal cylinder.In this study,an analytical approach to calculate the wave force on a partially immersed large-scale horizontal cylinder was formulated by using the stepwise approximation method.Physical model tests were conducted to investigate the effects of different factors(wave height,period,and immersion depth)on the wave force on a large-scale horizontal cylinder under conditions involving short-period waves.The results show that both horizontal and vertical wave forces on the cylinder increase as the wave height(immersion depth)increases in most cases.The vertical wave force decreases with the decrease of the period.For the horizontal wave force,it increases with the decrease of the period when the wavelength is larger than the diameter of the cylinder and decreases with the decrease of the period when the wavelength is smaller than the diameter of the cylinder.
基金funded by the National Natural Science Foundation of China(No.51809135)the Shandong Provincial Natural Science Foundation(No.ZR2018BEE 047)+1 种基金the National Natural Science Foundation of China–Shandong Joint Fund(No.U2006229)the SKL of HESS(No.HESS-1808).
文摘The selection of wave force models will significantly impact the structural responses of floating wind turbines.In this study,comparisons of wave force model effects on the structural responses and fatigue loads of a semi-submersible floating wind turbine(SFWT)were conducted.Simulations were performed by employing the Morison equation(ME)with linear or second-order wave kinematics and potential flow theory(PFT)with first-or second-order wave forces.A comparison of regular waves,irregular waves,and coupled wind/waves analyses with the experimental data showed that many of the simulation results and experimental data are relatively consistent.However,notable discrepancies are found in the response amplitude operators for platform heave,tower base bending moment,and tension in mooring lines.PFT models give more satisfactory results of heave but more significant discrepan-cies in tower base bending moment than the ME models.In irregular wave analyses,low-frequency resonances were captured by PFT models with second-order difference-frequency terms,and high-frequency resonances were captured by the ME models or PFT models with second-order sum-frequency terms.These force models capture the response frequencies but do not reasonably predict the response amplitudes.The coupled wind/waves analyses showed more satisfactory results than the wave-only analyses.However,an important detail to note is that this satisfactory result is based on the overprediction of wind-induced responses.
文摘In this paper, we prove the existence of forced waves for Leslie-Gower prey-predator model with nonlocal effects under shifting environment. By constructing a pair of upper and lower solutions with the method of monotone iteration, we can obtain the existence of forced waves for any positive constant shifting speed. Finally, we show the asymptotical behavior of traveling wave fronts in two tails.
文摘Based on model tests, the lift and resultant forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in this paper. The lift and resultant force coefficients CL and Cf related to KC number and the effect of direction of wave propagation are also given, which may be useful for practical engineering application.
文摘The total transverse forces on each of the two piles in the side-by-side arrangement and tandem arrangement are experimentally investigated in irregular waves and the total in-line wave forces are measured simultaneously. The statistical and spectral characteristics of the transverse forces are analyzed. The ratio of the transverse force on each pile in group to that on a single pile is defined as the transverse groupling-pile factor, KGL. Both the transverse coefficients CLG and KGL for each pile in array are varied with the relative pile distance and KC number and their relationships are presented in this paper. Also the ratio of the resultant wave froce of in-line force and transverse force to the in-line force and the vriation of the resultant coefficient are investigated.
文摘The purpose of this study is to develop an analytical formalism and derive series expansions for the time-averaged force and torque exerted on a compound coated compressible liquid-like cylinder,insonified by acoustic standing waves having an arbitrary angle of incidence in the polar(transverse)plane.The host medium of wave propagation and the eccentric liquid-like cylinder are non-viscous.Numerical computations illustrate the theoretical analysis with particular emphases on the eccentricity of the cylinder,the angle of incidence and the dimensionless size parameters of the inner and coating cylindrical fluid materials.The method to derive the acoustical scattering,and radiation force and torque components conjointly uses modal matching with the addition theorem,which adequately account for the multiple wave interaction effects between the layer and core fluid materials.The results demonstrate that longitudinal and lateral radiation force components arise.Moreover,an axial radiation torque component is quantified and computed for the non-absorptive compound cylinder,arising from geometrical asymmetry considerations as the eccentricity increases.The computational results reveal the emergence of neutral,positive,and negative radiation force and torque depending on the size parameter of the cylinder,the eccentricity,and the angle of incidence of the insonifying field.Moreover,based on the law of energy conservation applied to scattering,numerical verification is accomplished by computing the extinction/scattering energy efficiency.The results may find some related applications in fluid dynamics,particle trapping,mixing and manipulation using acoustical standing waves.
基金supported by the Knowledge Innovation Key Program of the Chinese Academy of Sciences (Grant No. KZCX1-YW-12)the National Key Science Foundation of China (Grant No. 41030855)
文摘By using a weakly nonlinear and perturbation method, the generalized inhomogeneous Korteweg de Vries (KdV)- Burgers equation is derived, which governs the evolution of the amplitude of Rossby waves under the influence of dissipation and slowly varying topography with time. The analysis indicates that dissipation and slowly varying topography with time are important factors in causing variation in the mass and energy of solitary waves.
文摘During reflection from a solid vertical wall, surface gravity waves produce a steady force on the wall, which was calculated earlier by the momentum method. Recently the linear momentum of these waves has been estimated to be twice as large as deduced from the classical Stokes drift formula. Therefore, the magnitude of the reflected wave force has been doubled here and the algebraic form of the equation is converted to be more understandable physically. Wave force equals fluid density times the square of the particle’s orbital speed and a numerical constant. Observations are welcomed to compare with the theory.
文摘The hydrodynamic interaction between two vertical cylinders in water waves is investigated based on the linearized potential flow theory. One of the two cylinders is fixed at the bottom while the other is articulated at the bottom and oscillates with small amplitudes in the direction of the incident wave. Both the diffracted wave and the radiation wave are studied in the present paper. A simple analytical expression for the velocity potential on the surface of each cylinder is obtained by means of Graf's addition theorem. The wave-excited forces and moments on the cylinders, the added masses and the radiation damping coefficients of the oscillating cylinder are all expressed explicitly in series form. The coefficients of the series are determined by solving algebraic equations. Several numerical examples are given to illustrate the effects of various parameters, such as the separation distance, the relative size of the cylinders, and the incident angle, on the first-order and steady second-order forces, the added masses and radiation-damping coefficients as well as the response of the oscillating cylinder.
文摘The total inline wave forces, the irregular wave forces in particular, on an isolated pile are investigated by experiment. The relationships between force coefficients Cd and CM including in Morison's Eq. . and KC number or Reynolds number Re, and the variation of Cd and Cm in frequency domain are analysed with the method of least-squares in time domain and that of cross-spectral analysis. The plots of C4and Cmversus KCare given for both regular and irregular waves and those for irregular waves are used for numerical simulation of the irregular wave forces on the vertical pile and the results are in fairly good agreement with the test data. Based on the experimental results , the applicability of the spectral analysis method for calculating irregular wave forces on an isolated pile is investigated with the coherency γ between wave and wave forces and with KC number.
文摘-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.