The LAGFD-WAM wave model is a third generation wave model. In the present paper the physical aspect of the model was shown in great detail including energy spectrum balance equation, complicated characteristics equati...The LAGFD-WAM wave model is a third generation wave model. In the present paper the physical aspect of the model was shown in great detail including energy spectrum balance equation, complicated characteristics equations and source functions.展开更多
Scale effect of ISWs loads on Floating Production Storage and Offloading(FPSO) is studied in this paper. The application conditions of KdV, eKdV and MCC ISWs theories are used in the numerical method. The depthaverage...Scale effect of ISWs loads on Floating Production Storage and Offloading(FPSO) is studied in this paper. The application conditions of KdV, eKdV and MCC ISWs theories are used in the numerical method. The depthaveraged velocities induced by ISWs are used for the velocity-inlet boundary. Three scale ratio numerical models λ=1, 20 and 300 were selected, which the scale ratio is the size ratio of numerical models to the experimental model.The comparisons between the numerical and former experimental results are performed to verify the feasibility of numerical method. The comparisons between the numerical and simplified theoretical results are performed to discuss the applicability of the simplified theoretical model summarized from the load experiments. Firstly, the numerical results of λ=1 numerical model showed a good agreement with former experimental and simplified theoretical results. It is feasible to simulate the ISWs loads on FPSO by the numerical method. Secondly, the comparisons between the results of three scale ratio numerical models and experimental results indicated that the scale ratios have more significant influence on the experimental horizontal forces than the vertical forces. The scale effect of horizontal forces mainly results from the different viscosity effects associated with the model’s dimension.Finally, through the comparisons between the numerical and simplified theoretical results for three scale ratio models, the simplified theoretical model of the pressure difference and friction forces exerted by ISWs on FPSO is applied for large-scale or full-scale FPSO.展开更多
This paper pnesents a third gneration shallow Whter disode spedtal wave nbotal medeIYE-WAM based on the spedtal action balance equation. The mode accounts for all edevan effectsof currents on waves, incuding tmpotally...This paper pnesents a third gneration shallow Whter disode spedtal wave nbotal medeIYE-WAM based on the spedtal action balance equation. The mode accounts for all edevan effectsof currents on waves, incuding tmpotally and spatialy varying depth and current inded refraction,sttalning and fequency shift and also explidtly takeS into aanunt all source terms, speclally adePth-limited breaking dheipation. In addition, an energy forcing scheme is propond and applied to themode’s open boundaries to areUn for the propagution of sedIs into the study spstem The upwinddiffeIenng scheme and a standard hybrid diffdrencing scheme for the propagaion terrn and a simpleEuler method for the source teme are employed.展开更多
A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for...A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for both bedload and suspended load sediment transport under combined waves and current conditions.The investigation examines the influence of several key parameters,including the rotation angle of sand waves relative to the main current,tidal current velocity amplitude,residual current,water depth,wave height,wave period,and wave direction,on sand wave evolution.The growth rate and migration rate of sand waves decrease as their rotation angle increases.For rotation angles smaller than 15°,sand wave evolution can be effectively simulated by a vertical 2D model with an error within 10%.The numerical results demonstrate that variations in tidal current velocity amplitude or residual current affect both vertical growth and horizontal migration of sand waves.As tidal current velocity amplitude and residual current increase,the growth rate initially rises to a maximum before decreasing.The migration rate shows a consistent increase with increasing tidal current amplitude and residual current.Under combined waves and current,both growth and migration rates decrease as water depth increases.With increasing wave height and period,the growth rate and migration rate initially rise to maximum values before declining,while showing a consistent increase with wave height and period.The change rate of sand waves reaches its maximum when wave propagation aligns parallel to tidal currents,and reaches its minimum when wave propagation is perpendicular to the currents.This phenomenon can be explained by the fluctuation of total bed shear stress relative to the angle of interaction between waves and current.展开更多
With different structural forms of ventilation pipes have various attenuation effects on incident shock waves while meeting ventilation requirements.The attenuation mechanism and the propagation law of shock waves in ...With different structural forms of ventilation pipes have various attenuation effects on incident shock waves while meeting ventilation requirements.The attenuation mechanism and the propagation law of shock waves in ventilation pipes of different structures are investigated by experiments and numerical simulations.Furthermore,for the same structure,the effects of peak pressure and positive pressure time on the attenuation rate are discussed.It is found that the attenuation rate increases with the incident shock wave pressure,and the shock wave attenuation rate tends to reach its limiting value k for the same structure and reasonably short positive pressure time.Under the same conditions,the attenuation rate is calculated using the pressure of the shock wave as follows:diffusion chamber pipe,branch pipe and selfconsumption pipe;the attenuation rate per unit volume is calculated as follows:self-consumption pipe,branch pipe and diffusion chamber pipe.In addition,an easy method is provided to calculate the attenuation rate of the shock wave in single and multi-stage ventilation pipes.Corresponding parameters are provided for various structures,and the margin of error between the formulae and experimental results is within 10%,which is significant for engineering applications.展开更多
The history of forecasting wind waves by wave energy conservation equation Is briefly described. Several currently used wave numerical models for shallow water based on different wave theories are discussed. Wave ener...The history of forecasting wind waves by wave energy conservation equation Is briefly described. Several currently used wave numerical models for shallow water based on different wave theories are discussed. Wave energy conservation models for the simulation of shallow water waves are introduced, with emphasis placed on the SWAN model, which takes use of the most advanced wave research achievements and has been applied to several theoretical and field conditions. The characteristics and applicability of the model, the finite difference numerical scheme of the action balance equation and its source terms computing methods are described in detail. The model has been verified with the propagation refraction numerical experiments for waves propagating in following and opposing currents; finally, the model is applied to the Haian Gulf area to simulate the wave height and wave period field there, and the results are compared with observed data.展开更多
A composite model, which is the combination of Boussinesq equations and Volume of Fluid (VOF) method, has been developed for 2-D time-domain computations of nonlinear waves in a large region. The whole computational r...A composite model, which is the combination of Boussinesq equations and Volume of Fluid (VOF) method, has been developed for 2-D time-domain computations of nonlinear waves in a large region. The whole computational region Omega is divided into two subregions. In the near-field around a structure, Omega(2), the flow is governed by 2-D Reynolds Averaged Navier-Stokes equations with a turbulence closure model of k-epsilon equations and numerically solved by the improved VOF method; whereas in the subregion Omega(1) (Omega(1) = Omega - Omega(2)) the flow is governed by one-D Boussinesq equations and numerically solved with the predictor-corrector algorithm. The velocity and the wave surface elevation are matched on the common boundary of the two subregions. Numerical tests have been conducted for the case of wave propagation and interaction with a wave barrier. It is shown that the composite model can help perform efficient computation of nonlinear waves in a large region with the complicated flow fields near structures taken into account.展开更多
In this paper the parameterizational approach of nonlinear source function and the implicit scheme of the model are discussed in detail. The matching problem is solved between time and space steps using the characteri...In this paper the parameterizational approach of nonlinear source function and the implicit scheme of the model are discussed in detail. The matching problem is solved between time and space steps using the characteristics inlaid scheme with very strong physical meaning. The computational comparison in typical winds shows some improvements to the WAM model. That the hindcast results of the model for typhoon cases are in good agreement with real data illustrates its applicability to wave forecast and engineering study.展开更多
The authors make an endeavor to explain why a new hybrid wave model is here proposed when several such models have already been in operation and the so- called third generation wave modej is proving attractive. This p...The authors make an endeavor to explain why a new hybrid wave model is here proposed when several such models have already been in operation and the so- called third generation wave modej is proving attractive. This part of the paper is devoted to the wind wave model. Both deep and shallow water models have been developed, the former being actually a special case of the latter when water depth is great. The deep water model is exceptionally simple in form. Significant wave height is the only prognostic variable. In comparison with the usual methods to compute the energy input and dissipations empirically or by 'tuning', the proposed model has the merit that the effects of all source terms are combined into one term which is computed through empirical growth relations for significant waves, these relations being, relatively speaking, easier and more reliable to obtain than those for the source terms in the spectral energy balance equation. The discrete part of the model and the implementation of the model as a whole will be discussed in the second part of the present paper.展开更多
The simulating waves nearshore(SWAN) model has typically been designed for wave simulations in near-shore regions. In this study, the model's applicability to the simulation of typhoon waves in the South China Sea...The simulating waves nearshore(SWAN) model has typically been designed for wave simulations in near-shore regions. In this study, the model's applicability to the simulation of typhoon waves in the South China Sea(SCS) was evaluated. A blended wind field, consisting of an interior domain based on Fujita's model and an exterior domain based on Takahashi's model, was used as the driving wind field. The waves driven by Typhoon Kai-tak over the SCS that occurred in 2012 were selected for the numerical simulation research. Sensitivity analyses of time step, grid resolution, and angle resolution were performed in order to obtain optimal model settings. Through sensitivity analyses, it can be found that the time step has a large influence on the results, while grid resolution and angle resolution have a little effect on the results.展开更多
In the present study a numerical model developed by Lynett and Liu （2002） is modified to include density difference in a stratified two-layer fluid in a three-dimensional internal wave domain. The internal solitary ...In the present study a numerical model developed by Lynett and Liu （2002） is modified to include density difference in a stratified two-layer fluid in a three-dimensional internal wave domain. The internal solitary wave （ISW） in the model is assumed to be weakly nonlinear and weakly dispersive, and the viscosity effects at all boundaries are ignored. The governing equations based on the Navier-Stokes and Euler equations are solved for internal solitary wave propagation over variable seabed topography. Theoretical formulations are established, from which analytical solutions are obtained, in addition to numerical results. Wave profiles from previous experimental studies are compared with the numerical results from the present analytical solutions. Numerical models developed on the basis of the present analytical solutions are better than those developed by Lynett and Liu （2002）. The results of numerical modeling agree well with the experimental data.展开更多
This article provides the application of the high-order, staggered-grid, finite-difference scheme to model elastic wave propagation in 3-D isotropic media. Here, we use second-order, tempo- ral- and high-order spatial...This article provides the application of the high-order, staggered-grid, finite-difference scheme to model elastic wave propagation in 3-D isotropic media. Here, we use second-order, tempo- ral- and high-order spatial finite-difference formulations with a staggered grid for discretization of the 3-D elastic wave equations of motion. The set of absorbing boundary conditions based on paraxial approximations of 3-D elastic wave equations are applied to the numerical boundaries. The trial re- sults for the salt model show that the numerical dispersion is decreased to a minimum extent, the accuracy high and diffracted waves abundant. It also shows that this method can be used for modeling wave propagation in complex media with the lateral variation of velocity.展开更多
Based on the mild slope equation that has heen deeomposed inlo three equations related to wave phase function, wave amplitude and wave approach angle, a refraction-diffraction model is developed. The finite difference...Based on the mild slope equation that has heen deeomposed inlo three equations related to wave phase function, wave amplitude and wave approach angle, a refraction-diffraction model is developed. The finite difference method has been selected as the solution method. The model results are compared with experimental results and the model is applied to coastal waters of the Fethiye Bay, whieh is located at the Mediterranean Sea of Turkey.展开更多
A numerical model for wave propagation in a harbour is verified by use of physical models. The extended time-dependent mild slope equation is employed as the governing equation, and the model is solved by use of ADI m...A numerical model for wave propagation in a harbour is verified by use of physical models. The extended time-dependent mild slope equation is employed as the governing equation, and the model is solved by use of ADI method containing the relaxation factor. Firstly, the reflection coefficient of waves in front of rubble-mound breakwaters under oblique incident waves is determined through physical model tests, and it is regarded as the basis for simulating partial reflection boundaries of the numerical model. Then model tests on refraction, diffraction and reflection of waves in a harbour are performed to measure wave height distribution. Comparative results between physical and numerical model tests show that the present numerical model can satisfactorily simulate the propagation of regular and irregular waves in a harbour with complex topography and boundary conditions.展开更多
This paper introduces a numerical model for studying the evolution of a periodic wave train, shoaling, and breaking in surf zone. The model can solve the Reynolds averaged Navier-Stokes （RANS） equations for a mean f...This paper introduces a numerical model for studying the evolution of a periodic wave train, shoaling, and breaking in surf zone. The model can solve the Reynolds averaged Navier-Stokes （RANS） equations for a mean flow, and the k-ε equations for turbulence kinetic energy k and turbulence dissipation rate ε. To track a free surface, the volume of fluid （VOF） function, satisfying the advection equation was introduced. In the numerical treatment, third-order upwind difference scheme was applied to the convection terms of the RANS equations in order to reduce the effect of numerical viscosity. The shoaling and breaking processes of a periodic wave train on gently sloping beaches were modeled. The computed wave heights of a sloping beach and the distribution of breaking wave pressure on a vertical wall were compared with laboratory data.展开更多
In the first part of the present paper we have explained why we manage to formulate another wave prediction model when so many of them, including the so-called third generation model, have already been in use. The win...In the first part of the present paper we have explained why we manage to formulate another wave prediction model when so many of them, including the so-called third generation model, have already been in use. The wind-wave part of the proposed model has also been given. Now we proceed to discuss the swell part,the implementation of the model as a prediction method,mumerical experiments done with ideal wind fields and hindcasts made in the Bohai Sea,in the neighboring seas adjacent to China and in the Northwest Pacific.展开更多
The wave-induced setup and circulation in a two dimensional horizontal(2DH)reef-lagoon-channel system is investigated by a non-hydrostatic model.The simulated results agree well with observations from the laboratory e...The wave-induced setup and circulation in a two dimensional horizontal(2DH)reef-lagoon-channel system is investigated by a non-hydrostatic model.The simulated results agree well with observations from the laboratory experiments,revealing that the model is valid in simulating wave transformation and currents over reefs.The effects of incident wave height,period,and reef flat water depth on the mean sea level and wave-driven currents are examined.Results show that the distributions of mean sea level and current velocities on the reef flat adjacent to the channel vary significantly from those in the area close to the side walls.From the wave averaged current field,an obvious alongshore flux flowing from the reef flat to the channel is captured.The flux from the reef flat composes the second source of the offshore rip current,while the first source is from the lagoon.A detailed momentum balance analysis shows that the alongshore current is mainly induced by the pressure gradient between the reef flat and the channel.In the lagoon,the momentum balances are between the pressure and radiation stress gradient,which drives flow towards the channel.Along the channel,the offshore current is mainly driven by the pressure gradient.展开更多
An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model （FEM） based Boussinesq equations is ap...An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model （FEM） based Boussinesq equations is applied for the numerical wave simulation, and a 2D piston-type wavemaker is used for the physical wave generation. An innovative scheme combining fourth-order Lagrange interpolation and Runge-Kutta scheme is described for solving the coupling equation. A Transfer function modulation method is presented to minimize the errors induced from the hydrodynamic invalidity of the coupling model and/or the mechanical capability of the wavemaker in area where nonlinearities or dispersion predominate. The overall performance and applicability of the coupling model has been experimentally validated by accounting for both regular and irregular waves and varying bathymetry. Experimental results show that the proposed numerical scheme and transfer function modulation method are efficient for the data transfer from the numerical model to the physical model up to a deterministic level.展开更多
The cold wave weather process in Jiujiang in the early spring of February 2020 was analyzed.The results show that the establishment of blocking high near Lake Baikal and the rapid southward of cold air after accumulat...The cold wave weather process in Jiujiang in the early spring of February 2020 was analyzed.The results show that the establishment of blocking high near Lake Baikal and the rapid southward of cold air after accumulation resulted in the cold wave weather accompanied by strong cooling,hale and rain(snow)weather in Jiujiang.Before the cold wave broke out,the ground warmed up significantly,which was also one of thermal conditions for this cold wave weather.Water vapor conditions were abundant at middle and low levels;at 850 hPa,temperature dropped by 12-14℃during February 14-15,and-4℃isotherm appeared in the southern part of central Jiangxi,which is a favorable condition for rain(snow)in most areas of Jiujiang.展开更多
On the basis of the new type Boussinesq equations （Madsen et al., 2002）, a set of equations explicitly including the effects of currents on waves are derived. A numerical implementation of the present equations in o...On the basis of the new type Boussinesq equations （Madsen et al., 2002）, a set of equations explicitly including the effects of currents on waves are derived. A numerical implementation of the present equations in one dimension is described. The numerical model is tested for wave propagation in a wave flume of uniform depth with current present. The present numerical results are compared with those of other researchers. It is validated that the present numerical model can reasonably reflect the nonlinear influences of currents on waves. Moreover, the effects of inputting different incident boundary conditions on the calculated results are studied.展开更多
文摘The LAGFD-WAM wave model is a third generation wave model. In the present paper the physical aspect of the model was shown in great detail including energy spectrum balance equation, complicated characteristics equations and source functions.
基金financially supported by the National Natural Science Foundation of China(Grant No.11372184)the National Basic Research Program of China(973 Program,Grant Nos.2015CB251203-3 and 2013CB036103)
文摘Scale effect of ISWs loads on Floating Production Storage and Offloading(FPSO) is studied in this paper. The application conditions of KdV, eKdV and MCC ISWs theories are used in the numerical method. The depthaveraged velocities induced by ISWs are used for the velocity-inlet boundary. Three scale ratio numerical models λ=1, 20 and 300 were selected, which the scale ratio is the size ratio of numerical models to the experimental model.The comparisons between the numerical and former experimental results are performed to verify the feasibility of numerical method. The comparisons between the numerical and simplified theoretical results are performed to discuss the applicability of the simplified theoretical model summarized from the load experiments. Firstly, the numerical results of λ=1 numerical model showed a good agreement with former experimental and simplified theoretical results. It is feasible to simulate the ISWs loads on FPSO by the numerical method. Secondly, the comparisons between the results of three scale ratio numerical models and experimental results indicated that the scale ratios have more significant influence on the experimental horizontal forces than the vertical forces. The scale effect of horizontal forces mainly results from the different viscosity effects associated with the model’s dimension.Finally, through the comparisons between the numerical and simplified theoretical results for three scale ratio models, the simplified theoretical model of the pressure difference and friction forces exerted by ISWs on FPSO is applied for large-scale or full-scale FPSO.
基金Supported by the National Eighty-Five-Year Project D09920109 and Chinese Academy of Sciences and State Education Commission
文摘This paper pnesents a third gneration shallow Whter disode spedtal wave nbotal medeIYE-WAM based on the spedtal action balance equation. The mode accounts for all edevan effectsof currents on waves, incuding tmpotally and spatialy varying depth and current inded refraction,sttalning and fequency shift and also explidtly takeS into aanunt all source terms, speclally adePth-limited breaking dheipation. In addition, an energy forcing scheme is propond and applied to themode’s open boundaries to areUn for the propagution of sedIs into the study spstem The upwinddiffeIenng scheme and a standard hybrid diffdrencing scheme for the propagaion terrn and a simpleEuler method for the source teme are employed.
基金the National Natural Science Foundation of China(Grant Nos.52371289 and 51979192).
文摘A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for both bedload and suspended load sediment transport under combined waves and current conditions.The investigation examines the influence of several key parameters,including the rotation angle of sand waves relative to the main current,tidal current velocity amplitude,residual current,water depth,wave height,wave period,and wave direction,on sand wave evolution.The growth rate and migration rate of sand waves decrease as their rotation angle increases.For rotation angles smaller than 15°,sand wave evolution can be effectively simulated by a vertical 2D model with an error within 10%.The numerical results demonstrate that variations in tidal current velocity amplitude or residual current affect both vertical growth and horizontal migration of sand waves.As tidal current velocity amplitude and residual current increase,the growth rate initially rises to a maximum before decreasing.The migration rate shows a consistent increase with increasing tidal current amplitude and residual current.Under combined waves and current,both growth and migration rates decrease as water depth increases.With increasing wave height and period,the growth rate and migration rate initially rise to maximum values before declining,while showing a consistent increase with wave height and period.The change rate of sand waves reaches its maximum when wave propagation aligns parallel to tidal currents,and reaches its minimum when wave propagation is perpendicular to the currents.This phenomenon can be explained by the fluctuation of total bed shear stress relative to the angle of interaction between waves and current.
文摘With different structural forms of ventilation pipes have various attenuation effects on incident shock waves while meeting ventilation requirements.The attenuation mechanism and the propagation law of shock waves in ventilation pipes of different structures are investigated by experiments and numerical simulations.Furthermore,for the same structure,the effects of peak pressure and positive pressure time on the attenuation rate are discussed.It is found that the attenuation rate increases with the incident shock wave pressure,and the shock wave attenuation rate tends to reach its limiting value k for the same structure and reasonably short positive pressure time.Under the same conditions,the attenuation rate is calculated using the pressure of the shock wave as follows:diffusion chamber pipe,branch pipe and selfconsumption pipe;the attenuation rate per unit volume is calculated as follows:self-consumption pipe,branch pipe and diffusion chamber pipe.In addition,an easy method is provided to calculate the attenuation rate of the shock wave in single and multi-stage ventilation pipes.Corresponding parameters are provided for various structures,and the margin of error between the formulae and experimental results is within 10%,which is significant for engineering applications.
基金"333"Project Scientific Research Foundation of Jiangsu ProvinceScience Fundation of Hohai University(3853)
文摘The history of forecasting wind waves by wave energy conservation equation Is briefly described. Several currently used wave numerical models for shallow water based on different wave theories are discussed. Wave energy conservation models for the simulation of shallow water waves are introduced, with emphasis placed on the SWAN model, which takes use of the most advanced wave research achievements and has been applied to several theoretical and field conditions. The characteristics and applicability of the model, the finite difference numerical scheme of the action balance equation and its source terms computing methods are described in detail. The model has been verified with the propagation refraction numerical experiments for waves propagating in following and opposing currents; finally, the model is applied to the Haian Gulf area to simulate the wave height and wave period field there, and the results are compared with observed data.
基金Trans-Century Training program Fund for the Talent,Ministry of Education of China
文摘A composite model, which is the combination of Boussinesq equations and Volume of Fluid (VOF) method, has been developed for 2-D time-domain computations of nonlinear waves in a large region. The whole computational region Omega is divided into two subregions. In the near-field around a structure, Omega(2), the flow is governed by 2-D Reynolds Averaged Navier-Stokes equations with a turbulence closure model of k-epsilon equations and numerically solved by the improved VOF method; whereas in the subregion Omega(1) (Omega(1) = Omega - Omega(2)) the flow is governed by one-D Boussinesq equations and numerically solved with the predictor-corrector algorithm. The velocity and the wave surface elevation are matched on the common boundary of the two subregions. Numerical tests have been conducted for the case of wave propagation and interaction with a wave barrier. It is shown that the composite model can help perform efficient computation of nonlinear waves in a large region with the complicated flow fields near structures taken into account.
文摘In this paper the parameterizational approach of nonlinear source function and the implicit scheme of the model are discussed in detail. The matching problem is solved between time and space steps using the characteristics inlaid scheme with very strong physical meaning. The computational comparison in typical winds shows some improvements to the WAM model. That the hindcast results of the model for typhoon cases are in good agreement with real data illustrates its applicability to wave forecast and engineering study.
文摘The authors make an endeavor to explain why a new hybrid wave model is here proposed when several such models have already been in operation and the so- called third generation wave modej is proving attractive. This part of the paper is devoted to the wind wave model. Both deep and shallow water models have been developed, the former being actually a special case of the latter when water depth is great. The deep water model is exceptionally simple in form. Significant wave height is the only prognostic variable. In comparison with the usual methods to compute the energy input and dissipations empirically or by 'tuning', the proposed model has the merit that the effects of all source terms are combined into one term which is computed through empirical growth relations for significant waves, these relations being, relatively speaking, easier and more reliable to obtain than those for the source terms in the spectral energy balance equation. The discrete part of the model and the implementation of the model as a whole will be discussed in the second part of the present paper.
基金supported by the National Natural Science Foundation of China(Grants No.51239001,51179015,and 51509023)the Open Research Foundation of the Key Laboratory of the Pearl River Estuarine Dynamics and Associated Process Regulation,the Ministry of Water Resources(Grant No.2018KJ03)+1 种基金the Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province(Grant No.2017SS04)the Key Laboratory of Technology for Safeguarding of Maritime Rights and Interests and Application,State Oceanic Administration(Grant No.SCS1606)
文摘The simulating waves nearshore(SWAN) model has typically been designed for wave simulations in near-shore regions. In this study, the model's applicability to the simulation of typhoon waves in the South China Sea(SCS) was evaluated. A blended wind field, consisting of an interior domain based on Fujita's model and an exterior domain based on Takahashi's model, was used as the driving wind field. The waves driven by Typhoon Kai-tak over the SCS that occurred in 2012 were selected for the numerical simulation research. Sensitivity analyses of time step, grid resolution, and angle resolution were performed in order to obtain optimal model settings. Through sensitivity analyses, it can be found that the time step has a large influence on the results, while grid resolution and angle resolution have a little effect on the results.
文摘In the present study a numerical model developed by Lynett and Liu （2002） is modified to include density difference in a stratified two-layer fluid in a three-dimensional internal wave domain. The internal solitary wave （ISW） in the model is assumed to be weakly nonlinear and weakly dispersive, and the viscosity effects at all boundaries are ignored. The governing equations based on the Navier-Stokes and Euler equations are solved for internal solitary wave propagation over variable seabed topography. Theoretical formulations are established, from which analytical solutions are obtained, in addition to numerical results. Wave profiles from previous experimental studies are compared with the numerical results from the present analytical solutions. Numerical models developed on the basis of the present analytical solutions are better than those developed by Lynett and Liu （2002）. The results of numerical modeling agree well with the experimental data.
文摘This article provides the application of the high-order, staggered-grid, finite-difference scheme to model elastic wave propagation in 3-D isotropic media. Here, we use second-order, tempo- ral- and high-order spatial finite-difference formulations with a staggered grid for discretization of the 3-D elastic wave equations of motion. The set of absorbing boundary conditions based on paraxial approximations of 3-D elastic wave equations are applied to the numerical boundaries. The trial re- sults for the salt model show that the numerical dispersion is decreased to a minimum extent, the accuracy high and diffracted waves abundant. It also shows that this method can be used for modeling wave propagation in complex media with the lateral variation of velocity.
文摘Based on the mild slope equation that has heen deeomposed inlo three equations related to wave phase function, wave amplitude and wave approach angle, a refraction-diffraction model is developed. The finite difference method has been selected as the solution method. The model results are compared with experimental results and the model is applied to coastal waters of the Fethiye Bay, whieh is located at the Mediterranean Sea of Turkey.
文摘A numerical model for wave propagation in a harbour is verified by use of physical models. The extended time-dependent mild slope equation is employed as the governing equation, and the model is solved by use of ADI method containing the relaxation factor. Firstly, the reflection coefficient of waves in front of rubble-mound breakwaters under oblique incident waves is determined through physical model tests, and it is regarded as the basis for simulating partial reflection boundaries of the numerical model. Then model tests on refraction, diffraction and reflection of waves in a harbour are performed to measure wave height distribution. Comparative results between physical and numerical model tests show that the present numerical model can satisfactorily simulate the propagation of regular and irregular waves in a harbour with complex topography and boundary conditions.
基金Supported by the High-Tech Research and Development Program of China (863 Program, No. 2001AA633070 2003AA604040)the National Natural Science Foundation of China (No. 40476015).
文摘This paper introduces a numerical model for studying the evolution of a periodic wave train, shoaling, and breaking in surf zone. The model can solve the Reynolds averaged Navier-Stokes （RANS） equations for a mean flow, and the k-ε equations for turbulence kinetic energy k and turbulence dissipation rate ε. To track a free surface, the volume of fluid （VOF） function, satisfying the advection equation was introduced. In the numerical treatment, third-order upwind difference scheme was applied to the convection terms of the RANS equations in order to reduce the effect of numerical viscosity. The shoaling and breaking processes of a periodic wave train on gently sloping beaches were modeled. The computed wave heights of a sloping beach and the distribution of breaking wave pressure on a vertical wall were compared with laboratory data.
文摘In the first part of the present paper we have explained why we manage to formulate another wave prediction model when so many of them, including the so-called third generation model, have already been in use. The wind-wave part of the proposed model has also been given. Now we proceed to discuss the swell part,the implementation of the model as a prediction method,mumerical experiments done with ideal wind fields and hindcasts made in the Bohai Sea,in the neighboring seas adjacent to China and in the Northwest Pacific.
基金The Key Project of NSFC-Shangdong Joint Research Funding under contract No.U1906230the Fundamental Research Funds for the Central Universities under contract No.B200202064+1 种基金the National Natural Science Foundation of China under contract Nos 41930538 and 51879096Marine Science and Technology Innovation Project of Jiangsu Province under contract No.HY2018-15。
文摘The wave-induced setup and circulation in a two dimensional horizontal(2DH)reef-lagoon-channel system is investigated by a non-hydrostatic model.The simulated results agree well with observations from the laboratory experiments,revealing that the model is valid in simulating wave transformation and currents over reefs.The effects of incident wave height,period,and reef flat water depth on the mean sea level and wave-driven currents are examined.Results show that the distributions of mean sea level and current velocities on the reef flat adjacent to the channel vary significantly from those in the area close to the side walls.From the wave averaged current field,an obvious alongshore flux flowing from the reef flat to the channel is captured.The flux from the reef flat composes the second source of the offshore rip current,while the first source is from the lagoon.A detailed momentum balance analysis shows that the alongshore current is mainly induced by the pressure gradient between the reef flat and the channel.In the lagoon,the momentum balances are between the pressure and radiation stress gradient,which drives flow towards the channel.Along the channel,the offshore current is mainly driven by the pressure gradient.
基金supported by the National Natural Science Foundation of China(Grant Nos.51079023 and 51221961)the National Basic Research Program of China(973 Program,Grant Nos.2013CB036101 and 2011CB013703)
文摘An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model （FEM） based Boussinesq equations is applied for the numerical wave simulation, and a 2D piston-type wavemaker is used for the physical wave generation. An innovative scheme combining fourth-order Lagrange interpolation and Runge-Kutta scheme is described for solving the coupling equation. A Transfer function modulation method is presented to minimize the errors induced from the hydrodynamic invalidity of the coupling model and/or the mechanical capability of the wavemaker in area where nonlinearities or dispersion predominate. The overall performance and applicability of the coupling model has been experimentally validated by accounting for both regular and irregular waves and varying bathymetry. Experimental results show that the proposed numerical scheme and transfer function modulation method are efficient for the data transfer from the numerical model to the physical model up to a deterministic level.
文摘The cold wave weather process in Jiujiang in the early spring of February 2020 was analyzed.The results show that the establishment of blocking high near Lake Baikal and the rapid southward of cold air after accumulation resulted in the cold wave weather accompanied by strong cooling,hale and rain(snow)weather in Jiujiang.Before the cold wave broke out,the ground warmed up significantly,which was also one of thermal conditions for this cold wave weather.Water vapor conditions were abundant at middle and low levels;at 850 hPa,temperature dropped by 12-14℃during February 14-15,and-4℃isotherm appeared in the southern part of central Jiangxi,which is a favorable condition for rain(snow)in most areas of Jiujiang.
基金supported by the National Natural Science Foundation of China (Grant No.40676053)theNational High Technology Research and Development Program of China (863 Program,Grant No.2006AA09A107)the Science and Technology Committee of Shanghai (Grant Nos.08DZ1203005 and 07DZ22027)
文摘On the basis of the new type Boussinesq equations （Madsen et al., 2002）, a set of equations explicitly including the effects of currents on waves are derived. A numerical implementation of the present equations in one dimension is described. The numerical model is tested for wave propagation in a wave flume of uniform depth with current present. The present numerical results are compared with those of other researchers. It is validated that the present numerical model can reasonably reflect the nonlinear influences of currents on waves. Moreover, the effects of inputting different incident boundary conditions on the calculated results are studied.
