Numerical wave tanks are widely-acknowledged tools in studying waves and wave-structure interactions. They can generate waves under realistic scales and offers more information on the fluid field. However, most numeri...Numerical wave tanks are widely-acknowledged tools in studying waves and wave-structure interactions. They can generate waves under realistic scales and offers more information on the fluid field. However, most numerical wave tanks suffer from issues known as the numerical dissipation and numerical dispersion. The former causes wave energy to be slowly dissipated and the latter shifts wave frequencies during wave propagation. This paper proposes a simple method of depressing numerical dissipation effects on the basis of solving Euler equations using the finite difference method(FDM). The wave propagation solutions are solved analytically taking into account the influence of the damping terms. The main idea of the method is to append a source term to the momentum equation, whose strength is determined by how strong the numerical damping effect is. The method is verified by successfully depressing numerical effects during the simulation of regular linear waves, Stokes waves and irregular waves. By applying the method, wave energy is able to be close to its initial value after long distance of travel.展开更多
Simulation of elastic wave propagation has important applications in many areas such as inverse problemand geophysical exploration.In this paper,stability conditions for wave simulation in 3-D anisotropic media with t...Simulation of elastic wave propagation has important applications in many areas such as inverse problemand geophysical exploration.In this paper,stability conditions for wave simulation in 3-D anisotropic media with the pseudospectral method are investigated.They can be expressed explicitly by elasticity constants which are easy to be applied in computations.The 3-Dwave simulation for two typical anisotropic media,transversely isotropic media and orthorhombic media,are carried out.The results demonstrate some satisfactory behaviors of the pseudospectral method.展开更多
The complexity of near surface intensifies the diversity of seismic wave fields,which makes study on near surface wavefields important in many aspects.The strong absorption of low velocity layer can affect the resolut...The complexity of near surface intensifies the diversity of seismic wave fields,which makes study on near surface wavefields important in many aspects.The strong absorption of low velocity layer can affect the resolution of seismic data,and free boundary can cause surface wave.Considering the above problems, we focus on the Rayleigh wavefields simulation using finite-difference wave equation of higher-order staggered grids and PML boundary conditions.Free boundary,buried source and overlying low velocity layer are taken into consideration and point explosion source is adopted.Through some numerical simulation with different parameters,we quantitatively analyze relationship between wave intensity and source depth,as well as the energy variation with propagation and obtain some practical knowledge and conclusions.展开更多
The ocean wave climate has a variety of applications in Naval defence.However,a long-term and reliable wave climate for the Indian Seas(The Arabian Sea and The Bay of Bengal)over a desired grid resolution could not be...The ocean wave climate has a variety of applications in Naval defence.However,a long-term and reliable wave climate for the Indian Seas(The Arabian Sea and The Bay of Bengal)over a desired grid resolution could not be established so far due to several constraints.In this study,an attempt was made for the simulation of wave climate for the Indian Seas using the third-generation wave model(3g-WAM)developed by WAMDI group.The 3g-WAM as such was implemented at NPOL for research applications.The specific importance of this investigation was that,the model utilized a“mean climatic year of winds”estimated using historical wind measurements following statistical and probabilistic approaches as the winds which were considered for this purpose were widely scattered in space and time.Model computations were carried out only for the deep waters with current refraction.The gridded outputs of various wave parameters were stored at each grid point and the spectral outputs were stored at selected locations.Monthly,seasonal and annual distributions of significant wave parameters were obtained by post-processing some of the model outputs.A qualitative validation of simulated wave height and period parameters were also carried out by comparing with the observed data.The study revealed that the results of the wave climate simulation were quite promising and they can be utilized for various operational and ocean engineering applications.Therefore,this study will be a useful reference/demonstration for conducting such experiments in the areas where wind as well as wave measurements are insufficient.展开更多
In 3D frequency domain seismic forward and inversion calculation,the huge amount of calculation and storage is one of the main factors that restrict the processing speed and calculation efficiency.The frequency domain...In 3D frequency domain seismic forward and inversion calculation,the huge amount of calculation and storage is one of the main factors that restrict the processing speed and calculation efficiency.The frequency domain finite-difference forward simulation algorithm based on the acoustic wave equation establishes a large bandwidth complex matrix according to the discretized acoustic wave equation,and then the frequency domain wave field value is obtained by solving the matrix equation.In this study,the predecessor's optimized five-point method is extended to a 3D seven-point finite-difference scheme,and then a perfectly matched layer absorbing boundary condition(PML)is added to establish the corresponding matrix equation.In order to solve the complex matrix,we transform it to the equivalent real number domain to expand the solvable range of the matrix,and establish two objective functions to transform the matrix solving problem into an optimization problem that can be solved using gradient methods,and then use conjugate gradient algorithm to solve the problem.Previous studies have shown that in the conjugate gradient algorithm,the product of the matrix and the vector is the main factor that affects the calculation efficiency.Therefore,this study proposes a method that transform bandwidth matrix and vector product problem into some equivalent vector and vector product algorithm,thereby reducing the amount of calculation and storage.展开更多
Due to the inference of the uneven shallow water seabed and the surrounding islands,the wind-generated waves around or in a reef lagoon are rather complicated,and critical to the safety of floating structures deployed...Due to the inference of the uneven shallow water seabed and the surrounding islands,the wind-generated waves around or in a reef lagoon are rather complicated,and critical to the safety of floating structures deployed near islands or inside a lagoon.This paper aims to find a feasible analysis tool for the wave simulations near islands and reefs.The proposed three methods of grid techniques of WAVEWATCH III(WW3)are assessed by using on-site measured data which was collected and accumulated for about 5 years since August 2014 by a wave observation system deployed inside and outside a reef lagoon in South China Sea.In the assessments,the wave statistics including the correlation coefficients,root mean square errors,and their variances are used to quantify the precisions of the simulation results of the significant wave heights,mean wave periods,and peak wave directions at two sites.Among the three methods,the Multi-scale Zone and Multi-scale grid Technique(MZMGT)established on unstructured triangular grids exhibits better results in terms of the accuracy and CPU cost.In addition,the bimodal feature of wave spectra was observed at both sites of the reef lagoon in different typhoon events.The wave characteristics inside the reef lagoon and open sea are also analyzed.展开更多
Despite their importance in the ocean environment,the key physical processes in wind-wave interactions are poorly understood.Using a solver developed for undulatory boundaries,we perform numerical simulations of the w...Despite their importance in the ocean environment,the key physical processes in wind-wave interactions are poorly understood.Using a solver developed for undulatory boundaries,we perform numerical simulations of the wind-wave system under various sea conditions,including wind over monochromatic waves,early wind-wave generation,and wind over a broadband wave field.Our results show that the wave direction and wave age can significantly change the distribution of streamwise vorticity in the wind field.Different wave patterns are observed in the process of wind-wave generation.In a broadband wave field,the wave growth rate due to wind input is found to depend on the wave steepness.展开更多
基金The National Natural Science Foundation of China under contract No.51609101 and 51909103the Natural Science Foundation of Fujian Province of China under contract Nos 2017J01701,2017J05085 and 2018J05090the Outstanding Young University Scientific Research Talents Cultivation Plan of Fujian Province of China
文摘Numerical wave tanks are widely-acknowledged tools in studying waves and wave-structure interactions. They can generate waves under realistic scales and offers more information on the fluid field. However, most numerical wave tanks suffer from issues known as the numerical dissipation and numerical dispersion. The former causes wave energy to be slowly dissipated and the latter shifts wave frequencies during wave propagation. This paper proposes a simple method of depressing numerical dissipation effects on the basis of solving Euler equations using the finite difference method(FDM). The wave propagation solutions are solved analytically taking into account the influence of the damping terms. The main idea of the method is to append a source term to the momentum equation, whose strength is determined by how strong the numerical damping effect is. The method is verified by successfully depressing numerical effects during the simulation of regular linear waves, Stokes waves and irregular waves. By applying the method, wave energy is able to be close to its initial value after long distance of travel.
基金supported by the 973 State Key Project under the grant No.2010 CB731505supported by the key national natural science foundation of China under the grant No.10431030the Chair foundation of State Key Laboratory of Scientific and Engineering Computing(LSEC).
文摘Simulation of elastic wave propagation has important applications in many areas such as inverse problemand geophysical exploration.In this paper,stability conditions for wave simulation in 3-D anisotropic media with the pseudospectral method are investigated.They can be expressed explicitly by elasticity constants which are easy to be applied in computations.The 3-Dwave simulation for two typical anisotropic media,transversely isotropic media and orthorhombic media,are carried out.The results demonstrate some satisfactory behaviors of the pseudospectral method.
基金support of the Major National Science and Technology Projects(No.2011ZX05006-002)the Fundamental Research Funds for the Central Universities of China(No.09CX04009A)
文摘The complexity of near surface intensifies the diversity of seismic wave fields,which makes study on near surface wavefields important in many aspects.The strong absorption of low velocity layer can affect the resolution of seismic data,and free boundary can cause surface wave.Considering the above problems, we focus on the Rayleigh wavefields simulation using finite-difference wave equation of higher-order staggered grids and PML boundary conditions.Free boundary,buried source and overlying low velocity layer are taken into consideration and point explosion source is adopted.Through some numerical simulation with different parameters,we quantitatively analyze relationship between wave intensity and source depth,as well as the energy variation with propagation and obtain some practical knowledge and conclusions.
文摘The ocean wave climate has a variety of applications in Naval defence.However,a long-term and reliable wave climate for the Indian Seas(The Arabian Sea and The Bay of Bengal)over a desired grid resolution could not be established so far due to several constraints.In this study,an attempt was made for the simulation of wave climate for the Indian Seas using the third-generation wave model(3g-WAM)developed by WAMDI group.The 3g-WAM as such was implemented at NPOL for research applications.The specific importance of this investigation was that,the model utilized a“mean climatic year of winds”estimated using historical wind measurements following statistical and probabilistic approaches as the winds which were considered for this purpose were widely scattered in space and time.Model computations were carried out only for the deep waters with current refraction.The gridded outputs of various wave parameters were stored at each grid point and the spectral outputs were stored at selected locations.Monthly,seasonal and annual distributions of significant wave parameters were obtained by post-processing some of the model outputs.A qualitative validation of simulated wave height and period parameters were also carried out by comparing with the observed data.The study revealed that the results of the wave climate simulation were quite promising and they can be utilized for various operational and ocean engineering applications.Therefore,this study will be a useful reference/demonstration for conducting such experiments in the areas where wind as well as wave measurements are insufficient.
基金supported by the National Natural Science Foundation of China(Project U1901602&41790465)Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0203)+2 种基金Shenzhen Key Laboratory of Deep Offshore Oil and Gas Exploration Technology(Grant No.ZDSYS20190902093007855)Shenzhen Science and Technology Program(Grant No.KQTD20170810111725321)the leading talents of Guangdong province program(Grant No.2016LJ06N652).
文摘In 3D frequency domain seismic forward and inversion calculation,the huge amount of calculation and storage is one of the main factors that restrict the processing speed and calculation efficiency.The frequency domain finite-difference forward simulation algorithm based on the acoustic wave equation establishes a large bandwidth complex matrix according to the discretized acoustic wave equation,and then the frequency domain wave field value is obtained by solving the matrix equation.In this study,the predecessor's optimized five-point method is extended to a 3D seven-point finite-difference scheme,and then a perfectly matched layer absorbing boundary condition(PML)is added to establish the corresponding matrix equation.In order to solve the complex matrix,we transform it to the equivalent real number domain to expand the solvable range of the matrix,and establish two objective functions to transform the matrix solving problem into an optimization problem that can be solved using gradient methods,and then use conjugate gradient algorithm to solve the problem.Previous studies have shown that in the conjugate gradient algorithm,the product of the matrix and the vector is the main factor that affects the calculation efficiency.Therefore,this study proposes a method that transform bandwidth matrix and vector product problem into some equivalent vector and vector product algorithm,thereby reducing the amount of calculation and storage.
基金supported by the Ministry of Industry and Information Technology(Grant Nos.[2016]22,[2019]357)supported by the Ministry of Science and Technology(Grant No.2013CB36100)+3 种基金the National Key Research and Development Programof China(Grant No.2017YFB0202701)the Jiangsu Province Science Foundation for Youths(Grant No.BK20190151)the Natural Science Foundation of Hunan Province(Grant No.2019JJ50633)the Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)(Grant No.ZJW-2019-08).
文摘Due to the inference of the uneven shallow water seabed and the surrounding islands,the wind-generated waves around or in a reef lagoon are rather complicated,and critical to the safety of floating structures deployed near islands or inside a lagoon.This paper aims to find a feasible analysis tool for the wave simulations near islands and reefs.The proposed three methods of grid techniques of WAVEWATCH III(WW3)are assessed by using on-site measured data which was collected and accumulated for about 5 years since August 2014 by a wave observation system deployed inside and outside a reef lagoon in South China Sea.In the assessments,the wave statistics including the correlation coefficients,root mean square errors,and their variances are used to quantify the precisions of the simulation results of the significant wave heights,mean wave periods,and peak wave directions at two sites.Among the three methods,the Multi-scale Zone and Multi-scale grid Technique(MZMGT)established on unstructured triangular grids exhibits better results in terms of the accuracy and CPU cost.In addition,the bimodal feature of wave spectra was observed at both sites of the reef lagoon in different typhoon events.The wave characteristics inside the reef lagoon and open sea are also analyzed.
文摘Despite their importance in the ocean environment,the key physical processes in wind-wave interactions are poorly understood.Using a solver developed for undulatory boundaries,we perform numerical simulations of the wind-wave system under various sea conditions,including wind over monochromatic waves,early wind-wave generation,and wind over a broadband wave field.Our results show that the wave direction and wave age can significantly change the distribution of streamwise vorticity in the wind field.Different wave patterns are observed in the process of wind-wave generation.In a broadband wave field,the wave growth rate due to wind input is found to depend on the wave steepness.