Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity.However,the path that the rays travel along in media with irregular interfaces is not cl...Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity.However,the path that the rays travel along in media with irregular interfaces is not clear.Here we study the problem by simulation using a new approach of the spectral-element method with some overlapped elements（SEMO） that can accurately evaluate waves traveling along an irregular interface.Consequently,the head waves are separated from interface waves by a time window.Thus,their energy and arrival time changes can be analyzed independently.These analyses demonstrate that,contrary to the case for head waves propagating along a flat interface,there are two mechanisms for head waves traveling along an irregular interface：a refraction mechanism and transmission mechanism.That is,the head waves may be refracted waves propagating along the interface or transmitted waves induced by the waves propagating in the higher-velocity media.Such knowledge will be helpful in constructing a more accurate inversion method,such as head wave travel-time tomography,and in obtaining a more accurate model of subsurface structure which is very important for understanding the formation mechanism of some special areas,such as the Tibetan Plateau.展开更多
This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves....This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.展开更多
Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR1...Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR108 and KCS in 120 degree regular oblique wave conditions. WISDAM has the capability of handling 6DOF （six degrees of freedom） in ship motions. Finite volume method with structured and overlapping grid system is employed. The flow variables are described in staggered manner, i.e., velocity components arc defined at the face center while pressure is at the cell center. Computational results agree favorably well with existing towing tank results especially for ship motions. Computational results also show that ship with bulbous bow experience higher hydrodynamic loads on bow section.展开更多
A method of studying the contributions of leaky modes to the wave field is presented based on the analysis of the Riemann surface structure of the characteristic function, and the sensitivities of con- tributions to v...A method of studying the contributions of leaky modes to the wave field is presented based on the analysis of the Riemann surface structure of the characteristic function, and the sensitivities of con- tributions to various factors of interest are examimed. Numerical results show that their contributions to the compressional head wave are related to the distributions of complex poles on (-1, -1) and (0, -1) Riemann sheets on the frequency-wavenumber (ω - k) plane. For fast formations, their contributions are small, while for slow formations with large Poisson’s ratio, their contributions are large because of those complex poles with small imaginary parts near the compressional vertical branch cut. The decaying factor of the contributions of leaky modes is approximately proportional to 1/distance2.展开更多
This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading.In the model,the formulas that estimate a ship’s added resistance due to waves attacking from different heading ang...This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading.In the model,the formulas that estimate a ship’s added resistance due to waves attacking from different heading angles have been further developed.A correction factor is proposed to consider the nonlinear effect due to large waves in power estimation.The formulas are developed and verified by model tests of 5 ships in regular waves with various heading angles.The full-scale measurements from three different types of ships,i.e.,a PCTC,a container ship,and a chemical tanker,are used to validate the proposed model for speed loss prediction in irregular waves.The effect of the improved model for speed loss prediction on a ship’s voyage optimization is also investigated.The results indicate that a ship’s voyage optimization solutions can be significantly affected by the prediction accuracy of speed loss caused by waves.展开更多
A general solution of the Boussinesq equation is presented which solves the problem of interaction of any number of right-going and left-going solitary waves.The solution relies on the exact solu- tion of Gardner,Gree...A general solution of the Boussinesq equation is presented which solves the problem of interaction of any number of right-going and left-going solitary waves.The solution relies on the exact solu- tion of Gardner,Greene,Kruskal,and Miura(1967),and has the same degree of accuracy as that solution, but has a wider scope of application.It is much simpler than,but as accurate as,Hirota's exact solu- tion(1973)of the Boussinesq equation,to which the present solution is compared for the simplest case of two solitary waves in head-on collision.展开更多
In this paper,using the reductive perturbation method combined with the PLK method and two-parameter expansions,we treat the problem of head-on collision between two solitary waves described by the generalized Kortewe...In this paper,using the reductive perturbation method combined with the PLK method and two-parameter expansions,we treat the problem of head-on collision between two solitary waves described by the generalized Korteweg-de Vries equation (the gKdV equation) and obtain its second-order approximate solution.The results show that after the collision,the gKdV solitary waves preserve their profiles and during the collision,the maximum amplitute is the linear superposition of two maximum amplitudes of the impinging solitary waves.展开更多
The reflected field of pulsed cylindrical waves from a liquid-solid interface is studied by the numerical method and the experimental method. The reflected field is calculated and shown in gray pictures. The calculate...The reflected field of pulsed cylindrical waves from a liquid-solid interface is studied by the numerical method and the experimental method. The reflected field is calculated and shown in gray pictures. The calculated incident angles θn (n=1, 2, 3, ...) of a series of minimums (or nulls) on the reflected wavefront are presented. The measured angle of the minimum from Schlieren photograph is consistent with that by calculation. The appearance of minimums is explained by the interference between the reflected wave and the head wave, and by the radiated dissipation of the head wave. The leading phase angle of the head wave to the reflected wave is proved to be about 3π/4 by the numerical calculation.展开更多
In this paper, based on the equations presented in [2], the head-on collision between two solitary waves described by the modified KdV equation (the mKdVequation, for short) is investigated by using the reductive pert...In this paper, based on the equations presented in [2], the head-on collision between two solitary waves described by the modified KdV equation (the mKdVequation, for short) is investigated by using the reductive perturbation method combined with the PLK method. These waves propagate at the interface of a two-fluid system, in which the density ratio of the two fluids equals the square of the depth ratio of the fluids. The second order perturbation solution is obtained. It is found that in the case of disregarding the nonuniform phase shift, the solitary waves preserve their original profiles after collision, which agrees with Fornberg and Whitham's numerical result of overtaking collision[6] whereas after considering the nonuniform phase shift, the wave profiles may deform after collision.展开更多
Head-on collision between two hydroelastic solitary waves propagating at the surface of an incompressible and ideal fluid covered by a thin ice sheet is analytically studied by means of a singular perturbation method....Head-on collision between two hydroelastic solitary waves propagating at the surface of an incompressible and ideal fluid covered by a thin ice sheet is analytically studied by means of a singular perturbation method. The ice sheet is represented by the Plotnikov-Toland model with the help of the special Cosserat theory of hyperelastic shells and the Kirchhoff-Love plate theory,which yields the nonlinear and conservative expression for the bending forces. The shallow water assumption is taken for the fluid motion with the Boussinesq approximation. The resulting governing equations are solved asymptotically with the aid of the Poincaré-Lighthill-Kuo method,and the solutions up to the third order are explicitly presented. It is observed that solitary waves after collision do not change their shapes and amplitudes. The wave profile is symmetric before collision, and it becomes, after collision, unsymmetric and titled backward in the direction of wave propagation. The wave profile significantly reduces due to greater impacts of elastic plate and surface tension. A graphical comparison is presented with published results, and the graphical comparison between linear and nonlinear elastic plate models is also shown as a special case of our study.展开更多
Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave lin...Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave line source embedded in the solid is presented.During the derivation,the wave fields in the fluid layer and the semi-infinite solid are firstly constructed by using the generalized ray method and the fluid-solid interface reflection and transmission coefficients.Then,the analytical solution in the transformed domain is obtained by superposing these wave fields,and the analytical solution in the time domain by applying the analytical inverse Laplace transform method.The the head wave generation conditions and arrival times at the fluid-solid interface are derived through this solution.Through the use of numerical examples,the analytical solution is proved right and the impacts of the sloping angle on the hydrodynamic pressure in the sea,the seismic wave propagation in the seabed,the head wave,and the Scholte wave at the seawater-seabed interface are also addressed.展开更多
Deep structure and material properties of faults can be understood by observing and simulating the particular phase in a fault fracture zone. This paper reviews the development of fault-zone seismic waves in the seism...Deep structure and material properties of faults can be understood by observing and simulating the particular phase in a fault fracture zone. This paper reviews the development of fault-zone seismic waves in the seismological domain. The present research status of fault-zone head wave and trapped wave are summarized systematically. Based on recent progress in this field,the paper discusses the prospect on the utilization of seismic wave in fault structure research.展开更多
A devastating MW 7.7 earthquake struck near Mandalay,Myanmar,on March 28,2025,causing extensive damage and casualties across Myanmar and neighboring regions.The 2025 event occurred in a well-recognized seismic gap alo...A devastating MW 7.7 earthquake struck near Mandalay,Myanmar,on March 28,2025,causing extensive damage and casualties across Myanmar and neighboring regions.The 2025 event occurred in a well-recognized seismic gap along the Sagaing Fault.Here we focus on the mainshock rupture properties based on backprojection of teleseismic P waves and early aftershock locations,analysis of near-field seismic recordings for the mainshock initiation,and remotely triggered seismicity following the MW 7.7 mainshock.We find that the~500 km mainshock rupture can be revealed by both rapid back-projection of teleseismic P waves from multiple broadband arrays and early aftershock locations within about 3 h from the Thai Meteorological Department(TMD)catalog.The rupture speed went supershear in the southward propagation after the initial bilateral subshear ruptures,as expected for large strike-slip earthquakes of such sizes.Clear fault zone head waves that are reflected along a bimaterial fault interface are observed at the only near-fault station GE.NPW on the slower side about 2.6 km away from the Sagaing fault,consistent with the preferred direction of a supershear rupture propagating to the south.In addition,aftershocks from the regional TMD catalog appear to be located mostly to the east of the mainshock rupture.While we cannot completely rule out mis-locations from the one-sided station distribution,these off-fault seismicity could also be explained by reactivations of subsidiary faults within the Shan Plateau,or an eastward dipping of the mainshock rupture plane.Although no immediate foreshocks were found from several nearby stations,we identify one sub-event with magnitude~6 at the beginning of the mainshock with a slightly different focal mechanism about 20–30 km south of the hypocenter determined by the United States Geological Survey(USGS).The mainshock also occurred when the tidal stresses reached its maximum on the right-lateral strike-slip fault,likely indicating that the timing of the mainshock is modulated by the solid earth tides.We find a significant increase of seismic activity near the Thailand/Myanmar border,in multiple(geothermally active)regions of Yunnan province in Southwest China,as well as the Xingfengjian reservoir in the Guangdong province in South China.Because static stress changes from the mainshock are small but negative near the Thailand/Myanmar border,the occurrence of microseismicity in this and other regions can be mainly explained by remote triggering from dynamic stress changes of the mainshock rupture.Our analyses demonstrate the importance of rapid analysis on openly available seismic data and catalog to better understand the rupture properties and triggered seismicity following large earthquakes.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.40874027,90715020,and 90915012)the Institute of Geophysics of the China Earthquake Administration (Grant No.DQJB07B06)Special Public Welfare Industry (Grant Nos.20070804 and 200808008)
文摘Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity.However,the path that the rays travel along in media with irregular interfaces is not clear.Here we study the problem by simulation using a new approach of the spectral-element method with some overlapped elements（SEMO） that can accurately evaluate waves traveling along an irregular interface.Consequently,the head waves are separated from interface waves by a time window.Thus,their energy and arrival time changes can be analyzed independently.These analyses demonstrate that,contrary to the case for head waves propagating along a flat interface,there are two mechanisms for head waves traveling along an irregular interface：a refraction mechanism and transmission mechanism.That is,the head waves may be refracted waves propagating along the interface or transmitted waves induced by the waves propagating in the higher-velocity media.Such knowledge will be helpful in constructing a more accurate inversion method,such as head wave travel-time tomography,and in obtaining a more accurate model of subsurface structure which is very important for understanding the formation mechanism of some special areas,such as the Tibetan Plateau.
文摘This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.
文摘Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR108 and KCS in 120 degree regular oblique wave conditions. WISDAM has the capability of handling 6DOF （six degrees of freedom） in ship motions. Finite volume method with structured and overlapping grid system is employed. The flow variables are described in staggered manner, i.e., velocity components arc defined at the face center while pressure is at the cell center. Computational results agree favorably well with existing towing tank results especially for ship motions. Computational results also show that ship with bulbous bow experience higher hydrodynamic loads on bow section.
基金Supported by the National Natural Science Foundation of China (Grant No. 10534040)
文摘A method of studying the contributions of leaky modes to the wave field is presented based on the analysis of the Riemann surface structure of the characteristic function, and the sensitivities of con- tributions to various factors of interest are examimed. Numerical results show that their contributions to the compressional head wave are related to the distributions of complex poles on (-1, -1) and (0, -1) Riemann sheets on the frequency-wavenumber (ω - k) plane. For fast formations, their contributions are small, while for slow formations with large Poisson’s ratio, their contributions are large because of those complex poles with small imaginary parts near the compressional vertical branch cut. The decaying factor of the contributions of leaky modes is approximately proportional to 1/distance2.
基金Open access funding provided by Chalmers University of Technology.The authors acknowledge the financial support from the European Commission(Horizon 2020)project EcoSail(Grant Number 820593)We are also grateful to the support from the Swedish Foundation for International Cooperation in Research and Higher Education(CH2016-6673)+1 种基金National Natural Science Foundation of China(NSFC-51779202)The second author thanks the funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie(Grant Number 754412)and VGR MoRE2020.
文摘This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading.In the model,the formulas that estimate a ship’s added resistance due to waves attacking from different heading angles have been further developed.A correction factor is proposed to consider the nonlinear effect due to large waves in power estimation.The formulas are developed and verified by model tests of 5 ships in regular waves with various heading angles.The full-scale measurements from three different types of ships,i.e.,a PCTC,a container ship,and a chemical tanker,are used to validate the proposed model for speed loss prediction in irregular waves.The effect of the improved model for speed loss prediction on a ship’s voyage optimization is also investigated.The results indicate that a ship’s voyage optimization solutions can be significantly affected by the prediction accuracy of speed loss caused by waves.
文摘A general solution of the Boussinesq equation is presented which solves the problem of interaction of any number of right-going and left-going solitary waves.The solution relies on the exact solu- tion of Gardner,Greene,Kruskal,and Miura(1967),and has the same degree of accuracy as that solution, but has a wider scope of application.It is much simpler than,but as accurate as,Hirota's exact solu- tion(1973)of the Boussinesq equation,to which the present solution is compared for the simplest case of two solitary waves in head-on collision.
文摘In this paper,using the reductive perturbation method combined with the PLK method and two-parameter expansions,we treat the problem of head-on collision between two solitary waves described by the generalized Korteweg-de Vries equation (the gKdV equation) and obtain its second-order approximate solution.The results show that after the collision,the gKdV solitary waves preserve their profiles and during the collision,the maximum amplitute is the linear superposition of two maximum amplitudes of the impinging solitary waves.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 19604008 and 10074039).
文摘The reflected field of pulsed cylindrical waves from a liquid-solid interface is studied by the numerical method and the experimental method. The reflected field is calculated and shown in gray pictures. The calculated incident angles θn (n=1, 2, 3, ...) of a series of minimums (or nulls) on the reflected wavefront are presented. The measured angle of the minimum from Schlieren photograph is consistent with that by calculation. The appearance of minimums is explained by the interference between the reflected wave and the head wave, and by the radiated dissipation of the head wave. The leading phase angle of the head wave to the reflected wave is proved to be about 3π/4 by the numerical calculation.
文摘In this paper, based on the equations presented in [2], the head-on collision between two solitary waves described by the modified KdV equation (the mKdVequation, for short) is investigated by using the reductive perturbation method combined with the PLK method. These waves propagate at the interface of a two-fluid system, in which the density ratio of the two fluids equals the square of the depth ratio of the fluids. The second order perturbation solution is obtained. It is found that in the case of disregarding the nonuniform phase shift, the solitary waves preserve their original profiles after collision, which agrees with Fornberg and Whitham's numerical result of overtaking collision[6] whereas after considering the nonuniform phase shift, the wave profiles may deform after collision.
基金sponsored by the National Natural Science Foundation of China (No. 11472166)
文摘Head-on collision between two hydroelastic solitary waves propagating at the surface of an incompressible and ideal fluid covered by a thin ice sheet is analytically studied by means of a singular perturbation method. The ice sheet is represented by the Plotnikov-Toland model with the help of the special Cosserat theory of hyperelastic shells and the Kirchhoff-Love plate theory,which yields the nonlinear and conservative expression for the bending forces. The shallow water assumption is taken for the fluid motion with the Boussinesq approximation. The resulting governing equations are solved asymptotically with the aid of the Poincaré-Lighthill-Kuo method,and the solutions up to the third order are explicitly presented. It is observed that solitary waves after collision do not change their shapes and amplitudes. The wave profile is symmetric before collision, and it becomes, after collision, unsymmetric and titled backward in the direction of wave propagation. The wave profile significantly reduces due to greater impacts of elastic plate and surface tension. A graphical comparison is presented with published results, and the graphical comparison between linear and nonlinear elastic plate models is also shown as a special case of our study.
基金financially supported by the National Key R&D Program of China (Grant No.2021YFC3100700)the National Natural Science Foundation of China (Grant Nos.U2039209 and 41874067)the Natural Science Foundation of Heilongjiang Province,China (Grant No.YQ2021D010)。
文摘Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave line source embedded in the solid is presented.During the derivation,the wave fields in the fluid layer and the semi-infinite solid are firstly constructed by using the generalized ray method and the fluid-solid interface reflection and transmission coefficients.Then,the analytical solution in the transformed domain is obtained by superposing these wave fields,and the analytical solution in the time domain by applying the analytical inverse Laplace transform method.The the head wave generation conditions and arrival times at the fluid-solid interface are derived through this solution.Through the use of numerical examples,the analytical solution is proved right and the impacts of the sloping angle on the hydrodynamic pressure in the sea,the seismic wave propagation in the seabed,the head wave,and the Scholte wave at the seawater-seabed interface are also addressed.
基金sponsored by the Foundation of China Scholarship Council,the"Earthquake Science Talents Training Program"of China Earthquake Administration,the Sub-project of National Key Technology R&D Program(1012BAK19804-01-05)the Natural Science Foundation of Shandong Province(ZR2012DQ006),China
文摘Deep structure and material properties of faults can be understood by observing and simulating the particular phase in a fault fracture zone. This paper reviews the development of fault-zone seismic waves in the seismological domain. The present research status of fault-zone head wave and trapped wave are summarized systematically. Based on recent progress in this field,the paper discusses the prospect on the utilization of seismic wave in fault structure research.
基金supported by the National Nonprofit Fundamental Research Grant of China, Institute of Geology, China Earthquake Administration (grant number IGCEA2504)partially supported by National Science Foundation Grant RISE-2425889+1 种基金supported by Earthquake Prediction Open Fund, China Earthquake Administration (Grant No. XH25006D)supported by the International Partnership Program of Chinese Academy of Sciences (Grant No. 164GJHZ2023006MI)
文摘A devastating MW 7.7 earthquake struck near Mandalay,Myanmar,on March 28,2025,causing extensive damage and casualties across Myanmar and neighboring regions.The 2025 event occurred in a well-recognized seismic gap along the Sagaing Fault.Here we focus on the mainshock rupture properties based on backprojection of teleseismic P waves and early aftershock locations,analysis of near-field seismic recordings for the mainshock initiation,and remotely triggered seismicity following the MW 7.7 mainshock.We find that the~500 km mainshock rupture can be revealed by both rapid back-projection of teleseismic P waves from multiple broadband arrays and early aftershock locations within about 3 h from the Thai Meteorological Department(TMD)catalog.The rupture speed went supershear in the southward propagation after the initial bilateral subshear ruptures,as expected for large strike-slip earthquakes of such sizes.Clear fault zone head waves that are reflected along a bimaterial fault interface are observed at the only near-fault station GE.NPW on the slower side about 2.6 km away from the Sagaing fault,consistent with the preferred direction of a supershear rupture propagating to the south.In addition,aftershocks from the regional TMD catalog appear to be located mostly to the east of the mainshock rupture.While we cannot completely rule out mis-locations from the one-sided station distribution,these off-fault seismicity could also be explained by reactivations of subsidiary faults within the Shan Plateau,or an eastward dipping of the mainshock rupture plane.Although no immediate foreshocks were found from several nearby stations,we identify one sub-event with magnitude~6 at the beginning of the mainshock with a slightly different focal mechanism about 20–30 km south of the hypocenter determined by the United States Geological Survey(USGS).The mainshock also occurred when the tidal stresses reached its maximum on the right-lateral strike-slip fault,likely indicating that the timing of the mainshock is modulated by the solid earth tides.We find a significant increase of seismic activity near the Thailand/Myanmar border,in multiple(geothermally active)regions of Yunnan province in Southwest China,as well as the Xingfengjian reservoir in the Guangdong province in South China.Because static stress changes from the mainshock are small but negative near the Thailand/Myanmar border,the occurrence of microseismicity in this and other regions can be mainly explained by remote triggering from dynamic stress changes of the mainshock rupture.Our analyses demonstrate the importance of rapid analysis on openly available seismic data and catalog to better understand the rupture properties and triggered seismicity following large earthquakes.
