The internal solitary wave(ISW)represents a frequent and severe oceanic dynamic phenomenon observed in the South China Sea,exposing marine structures to sudden loads.This paper examines the prediction model of interac...The internal solitary wave(ISW)represents a frequent and severe oceanic dynamic phenomenon observed in the South China Sea,exposing marine structures to sudden loads.This paper examines the prediction model of interaction loads between ISW and FPSO,accounting for varying attack angles and incorporating ISW theories.The research demonstrates that the horizontal and transverse forces on FPSO under internal solitary waves(ISWs)comprise wave pressure difference force and viscous force,while the vertical force primarily consists of vertical wave pressure difference force.The wave pressure difference force is determined using the Froude-Krylov equation.The viscous force is derived from the tangential particle velocity induced by ISW and the viscous coefficient.The viscous coefficient formula is obtained through regression analysis of experimental data with different ISW attack angles.The research reveals that the horizontal viscous coefficient C_(vx)decreases as Reynolds number(R_(e))increases,while the transverse viscous coefficient C_(vy)initially increases and subsequently decreases with the growth of the Keulegan-Carpenter number(KC).Moreover,changes in wave propagation direction significantly affect the extreme magnitudes of both horizontal and transverse forces,and simultaneously modify the transverse force orientation,while having minimal impact on the vertical force.Additionally,the forces increase with the ISW’s amplitude.For horizontal and transverse forces,a thinner upper fluid layer generates larger forces.Comparative analysis of experimental,numerical,and theoretical results indicates strong agreement between theoretical predictions and experimental and numerical outcomes.展开更多
Internal solitary waves(ISWs)have considerable energy to drive the mixing of water masses in the Sulu Sea.The propagation speed is one of the critical parameters in quantifying the energy budget of the ISWs.We collect...Internal solitary waves(ISWs)have considerable energy to drive the mixing of water masses in the Sulu Sea.The propagation speed is one of the critical parameters in quantifying the energy budget of the ISWs.We collected 1354 groups of ISWs’speeds from tandem satellite remote sensing images with temporal intervals shorter than 25 min and analyzed their spatial and multi-scale temporal variations in the Sulu Sea.We found that water depth plays an important role in modulating the spatial variation of wave speeds,which increase exponentially with water depth with a power of 0.26.Tidal currents,ocean stratification,background circulation,and climate affect the temporal variations of wave speeds from days to months or years.The fortnightly spring/neap tidal currents cause daily variations of wave speeds up to 40%by modulating the ISW amplitudes.In addition to the well-accepted results that monthly variations of wave speeds are related to density stratification,we found that enhanced stratification increases wave speeds,and the background circulation leads to a maximum decrease of 0.27 m/s in the linear counterparts of wave speed.Moreover,the averaged wave speed collected in October is lower than the corresponding linear one possibly due to some unknown dynamical processes or underestimation of background current.As for the interannual variations,we show that wave speed increases in La Niña years and decreases in El Niño years as a result of the climatic modulation on the depth of the maximum value of buoyancy frequency.展开更多
Optical remote sensing has been widely used to study internal solitary waves(ISWs).Wind speed has an important effect on ISW imaging of optical remote sensing.The light and dark bands of ISWs cannot be observed by opt...Optical remote sensing has been widely used to study internal solitary waves(ISWs).Wind speed has an important effect on ISW imaging of optical remote sensing.The light and dark bands of ISWs cannot be observed by optical remote sensing when the wind is too strong.The relationship between the characteristics of ISWs bands in optical remote sensing images and the wind speed is still unclear.The influence of wind speeds on the characteristics of the ISWs bands is investigated based on the physical simulation experiments with the wind speeds of 1.6,3.1,3.5,3.8,and 3.9 m/s.The experimental results show that when the wind speed is 3.9 m/s,the ISWs bands cannot be observed in optical remote sensing images with the stratification of h_(1)∶h_(2)=7∶58,ρ_(1)∶ρ_(2)=1∶1.04.When the wind speeds are 3.1,3.5,and 3.8 m/s,which is lower than 3.9 m/s,the ISWs bands can be obtained in the simulated optical remote sensing image.The location of the band’s dark and light extremum and the band’s peak-to-peak spacing are almost not affected by wind speed.More-significant wind speeds can cause a greater gray difference of the light-dark bands.This provided a scientific basis for further understanding of ISW optical remote sensing imaging.展开更多
The dynamic parameters for internal solitary waves(ISWs)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of ISWs.The spatiotemporal variations of the...The dynamic parameters for internal solitary waves(ISWs)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of ISWs.The spatiotemporal variations of the dynamic parameters of the ISWs in the northern South China Sea(SCS)were studied based on the reanalysis of long-term temperature and salinity datasets.The results for spectrum analysis show that there are definite geographical differences for the periodic variation of the parameters:in shallow water,all parameters vary with a wave period of one year,while in deep water wave components of the parameters at other frequencies exist.Using wavelet analysis,the wavelet power spectral densities in deep water exhibited an inter-annual variation pattern.For example,the wave component of the dispersion coefficient with a wave period of about half a year reached its power peak once every two years.Based on previous work,this inter-annual variation pattern was deduced to be caused by dynamic processes.In further work on the regulatory mechanisms,empirical orthogonal function(EOF)decomposition was performed.It was found that the modes of the dispersion coefficient have different geographical distributions,explaining the reason why the wave components in different frequencies appeared in different locations.The numerical simulation results confirm that the variations in the parameters of the ISWs derived from the eKdV equation could affect the waveforms significantly because of changes in the polarity of the ISWs.Therefore,the periodic variations of the dynamic parameters are related to the geographical location because of dynamic processes operating.展开更多
Internal solitary waves(ISW),characterized by large amplitude and long propagation distance,are widespread in global oceans.While remote sensing images have played an essential role in studying ISWs,they mainly exploi...Internal solitary waves(ISW),characterized by large amplitude and long propagation distance,are widespread in global oceans.While remote sensing images have played an essential role in studying ISWs,they mainly exploit two-dimensional image information.However,with the launch of the surface water ocean topography(SWOT)satellite on December 16,2022,a unique opportunity has emerged to capture wide-swath three-dimensional ISW-induced sea surface information.In this study,we examine ISWs in the Andaman Sea using data from the Ka-band Radar Interferometer(KaRIN),a crucial sensor onboard SWOT.KaRIN not only provides backscattering satellite images but also employs synthetic aperture interferometry techniques to retrieve wide-swath two-dimensional sea surface height measurements.Our observations in the Andaman Sea revealed the presence of ISWs characterized by dark-bright strips and surface elevation solitons.The surface soliton has an amplitude of 0.32 m,resulting in an estimation of ISW amplitude of approximately 60 m.In contrast to traditional two-dimensional satellite images or nadir-looking altimetry data,the SWOT mission’s capability to capture threedimensional sea surface information represents a significant advancement.This breakthrough holds substantial promise for ISW studies,particularly in the context of ISW amplitude inversion.展开更多
According to the established prediction model of internal solitary wave loads on FPSO in the previous work,the lumped mass model and the movement equations of finite displacement in time domain,the dynamic response mo...According to the established prediction model of internal solitary wave loads on FPSO in the previous work,the lumped mass model and the movement equations of finite displacement in time domain,the dynamic response model of interaction between internal solitary waves and FPSO with mooring lines were established.Through calculations and analysis,time histories of dynamic loads of FPSO exerted by internal solitary waves,FPSO’s motion and dynamic tension of mooring line were obtained.The effects of the horizontal pretension of mooring line,the amplitude of internal solitary wave and layer fluid depth on dynamic response behavior of FPSO were mastered.It was shown that the internal solitary waves had significant influence on FPSO,such as the large magnitude horizontal drift and a sudden tension increment.With internal solitary wave of −170 m amplitude in the ocean with upper and lower layer fluid depth ratio being 60:550,the dynamic loads reached 991.132 kN(horizontal force),18067.3 kN(vertical force)and−5042.92 kN·m(pitching moment).Maximum of FPSO’s horizontal drift was 117.56 m.Tension increment of upstream mooring line approached 401.48 kN and that of backflow mooring line was−140 kN.Moreover,the loads remained nearly constant with different pretension but increased obviously with the changing amplitude and layer fluid depth ratio.Tension increments of mooring lines also changed little with the pretension but increased rapidly when amplitude and layer fluid depth ratio increased.However,FPSO’s motion increased quickly with not only the horizontal pretension but also the amplitude of internal solitary wave and layer fluid depth ratio.展开更多
An investigation into the prediction method for internal solitary waves(ISWs)loads on the columns and caissons of the semi-submersible platform found on three kinds of internal solitary wave theories and the modified ...An investigation into the prediction method for internal solitary waves(ISWs)loads on the columns and caissons of the semi-submersible platform found on three kinds of internal solitary wave theories and the modified Morison Equation is described.The characteristics of loads exerted on the semi-submersible platform model caused by the ISWs have been observed experimentally,and the inertial and drag coefficients in Morison Equation are determined by analyzing the forces of experiments.From the results,it is of interest to find that Reynolds number,KC number and layer thickness ratio have a considerable influence on the coefficients.The direction of incoming waves,how-ever,is almost devoid of effects on the coefficients.The drag coefficient of columns varies as an exponential function of Reynolds number,and inertia coefficient of columns is a power function related to KC number.Meanwhile,the drag coefficient of caissons is approximately constant in terms of regression analysis of experimental data.The results from different experimental conditions reveal that the inertia coefficient of caissons appears to be exponential correlated with upper layer depths.展开更多
Internal solitary waves （ISWs） are frequently observed in the area between Dongsha Island （DI） and Taiwan Island. However, there have been few in-situ observations southwest of DI. To improve our knowledge of ISWs...Internal solitary waves （ISWs） are frequently observed in the area between Dongsha Island （DI） and Taiwan Island. However, there have been few in-situ observations southwest of DI. To improve our knowledge of ISWs in this area, we observed the ISWs over the continental shelf （115.4°E, 20.3°N） from Aug. 29 to Oct. 10, 2011 with temperature sensors and an acoustic Doppler current profiler （ADCP）. The observations showed that the a fully developed ISW produced a current whose maximum westward velocity was 0.92 rrds and maximum northward velocity was 0.47 m/s. During the 41-day observation period the ISWs appeared for three periods with about 7-day gaps between each period. During each day, two types of ISWs were observed. The first type of wave arrived regularly diurnally at the same time each day, with a similar pattern to that of the type-a wave identified by Ramp et al. （2004）. The second type arrived about 12 h after the first type and was delayed about 1 hour each day; this wave type was related to the type-b wave. Thus, our observations confirmed that both type-a and type-b waves can reach the area southwest of the DI. Moreover, the waves observed by the mooring propagated toward the directions of 270°-315° clockwise from true north, indicating obvious refraction from uneven topography around DI.展开更多
基金supported by JUST Start-up Fund for Science Research,the Jiangsu Natural Science Foundation(Grant No.BK20210885).
文摘The internal solitary wave(ISW)represents a frequent and severe oceanic dynamic phenomenon observed in the South China Sea,exposing marine structures to sudden loads.This paper examines the prediction model of interaction loads between ISW and FPSO,accounting for varying attack angles and incorporating ISW theories.The research demonstrates that the horizontal and transverse forces on FPSO under internal solitary waves(ISWs)comprise wave pressure difference force and viscous force,while the vertical force primarily consists of vertical wave pressure difference force.The wave pressure difference force is determined using the Froude-Krylov equation.The viscous force is derived from the tangential particle velocity induced by ISW and the viscous coefficient.The viscous coefficient formula is obtained through regression analysis of experimental data with different ISW attack angles.The research reveals that the horizontal viscous coefficient C_(vx)decreases as Reynolds number(R_(e))increases,while the transverse viscous coefficient C_(vy)initially increases and subsequently decreases with the growth of the Keulegan-Carpenter number(KC).Moreover,changes in wave propagation direction significantly affect the extreme magnitudes of both horizontal and transverse forces,and simultaneously modify the transverse force orientation,while having minimal impact on the vertical force.Additionally,the forces increase with the ISW’s amplitude.For horizontal and transverse forces,a thinner upper fluid layer generates larger forces.Comparative analysis of experimental,numerical,and theoretical results indicates strong agreement between theoretical predictions and experimental and numerical outcomes.
基金Supported by the National Natural Science Foundation of China(Nos.U23A2032,42006193)supported by the Hainan Provincial Excellent Talent Team Project(Space Observation of Deep-sea)。
文摘Internal solitary waves(ISWs)have considerable energy to drive the mixing of water masses in the Sulu Sea.The propagation speed is one of the critical parameters in quantifying the energy budget of the ISWs.We collected 1354 groups of ISWs’speeds from tandem satellite remote sensing images with temporal intervals shorter than 25 min and analyzed their spatial and multi-scale temporal variations in the Sulu Sea.We found that water depth plays an important role in modulating the spatial variation of wave speeds,which increase exponentially with water depth with a power of 0.26.Tidal currents,ocean stratification,background circulation,and climate affect the temporal variations of wave speeds from days to months or years.The fortnightly spring/neap tidal currents cause daily variations of wave speeds up to 40%by modulating the ISW amplitudes.In addition to the well-accepted results that monthly variations of wave speeds are related to density stratification,we found that enhanced stratification increases wave speeds,and the background circulation leads to a maximum decrease of 0.27 m/s in the linear counterparts of wave speed.Moreover,the averaged wave speed collected in October is lower than the corresponding linear one possibly due to some unknown dynamical processes or underestimation of background current.As for the interannual variations,we show that wave speed increases in La Niña years and decreases in El Niño years as a result of the climatic modulation on the depth of the maximum value of buoyancy frequency.
基金Supported by the National Natural Science Foundation of China(Nos.61871353,42006164)。
文摘Optical remote sensing has been widely used to study internal solitary waves(ISWs).Wind speed has an important effect on ISW imaging of optical remote sensing.The light and dark bands of ISWs cannot be observed by optical remote sensing when the wind is too strong.The relationship between the characteristics of ISWs bands in optical remote sensing images and the wind speed is still unclear.The influence of wind speeds on the characteristics of the ISWs bands is investigated based on the physical simulation experiments with the wind speeds of 1.6,3.1,3.5,3.8,and 3.9 m/s.The experimental results show that when the wind speed is 3.9 m/s,the ISWs bands cannot be observed in optical remote sensing images with the stratification of h_(1)∶h_(2)=7∶58,ρ_(1)∶ρ_(2)=1∶1.04.When the wind speeds are 3.1,3.5,and 3.8 m/s,which is lower than 3.9 m/s,the ISWs bands can be obtained in the simulated optical remote sensing image.The location of the band’s dark and light extremum and the band’s peak-to-peak spacing are almost not affected by wind speed.More-significant wind speeds can cause a greater gray difference of the light-dark bands.This provided a scientific basis for further understanding of ISW optical remote sensing imaging.
基金Supported by the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2023JJ10053)the National Natural Science Foundation of China(No.42276205)。
文摘The dynamic parameters for internal solitary waves(ISWs)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of ISWs.The spatiotemporal variations of the dynamic parameters of the ISWs in the northern South China Sea(SCS)were studied based on the reanalysis of long-term temperature and salinity datasets.The results for spectrum analysis show that there are definite geographical differences for the periodic variation of the parameters:in shallow water,all parameters vary with a wave period of one year,while in deep water wave components of the parameters at other frequencies exist.Using wavelet analysis,the wavelet power spectral densities in deep water exhibited an inter-annual variation pattern.For example,the wave component of the dispersion coefficient with a wave period of about half a year reached its power peak once every two years.Based on previous work,this inter-annual variation pattern was deduced to be caused by dynamic processes.In further work on the regulatory mechanisms,empirical orthogonal function(EOF)decomposition was performed.It was found that the modes of the dispersion coefficient have different geographical distributions,explaining the reason why the wave components in different frequencies appeared in different locations.The numerical simulation results confirm that the variations in the parameters of the ISWs derived from the eKdV equation could affect the waveforms significantly because of changes in the polarity of the ISWs.Therefore,the periodic variations of the dynamic parameters are related to the geographical location because of dynamic processes operating.
基金Supported by the National Key Research and Development Program of China(No.2022YFE0204600)the National Natural Science Foundation for Young Scientists of China(No.41906157)。
文摘Internal solitary waves(ISW),characterized by large amplitude and long propagation distance,are widespread in global oceans.While remote sensing images have played an essential role in studying ISWs,they mainly exploit two-dimensional image information.However,with the launch of the surface water ocean topography(SWOT)satellite on December 16,2022,a unique opportunity has emerged to capture wide-swath three-dimensional ISW-induced sea surface information.In this study,we examine ISWs in the Andaman Sea using data from the Ka-band Radar Interferometer(KaRIN),a crucial sensor onboard SWOT.KaRIN not only provides backscattering satellite images but also employs synthetic aperture interferometry techniques to retrieve wide-swath two-dimensional sea surface height measurements.Our observations in the Andaman Sea revealed the presence of ISWs characterized by dark-bright strips and surface elevation solitons.The surface soliton has an amplitude of 0.32 m,resulting in an estimation of ISW amplitude of approximately 60 m.In contrast to traditional two-dimensional satellite images or nadir-looking altimetry data,the SWOT mission’s capability to capture threedimensional sea surface information represents a significant advancement.This breakthrough holds substantial promise for ISW studies,particularly in the context of ISW amplitude inversion.
基金supported by JUST start-up fund for science research,the Jiangsu Natural Science Foundation(Grant No.BK20210885).
文摘According to the established prediction model of internal solitary wave loads on FPSO in the previous work,the lumped mass model and the movement equations of finite displacement in time domain,the dynamic response model of interaction between internal solitary waves and FPSO with mooring lines were established.Through calculations and analysis,time histories of dynamic loads of FPSO exerted by internal solitary waves,FPSO’s motion and dynamic tension of mooring line were obtained.The effects of the horizontal pretension of mooring line,the amplitude of internal solitary wave and layer fluid depth on dynamic response behavior of FPSO were mastered.It was shown that the internal solitary waves had significant influence on FPSO,such as the large magnitude horizontal drift and a sudden tension increment.With internal solitary wave of −170 m amplitude in the ocean with upper and lower layer fluid depth ratio being 60:550,the dynamic loads reached 991.132 kN(horizontal force),18067.3 kN(vertical force)and−5042.92 kN·m(pitching moment).Maximum of FPSO’s horizontal drift was 117.56 m.Tension increment of upstream mooring line approached 401.48 kN and that of backflow mooring line was−140 kN.Moreover,the loads remained nearly constant with different pretension but increased obviously with the changing amplitude and layer fluid depth ratio.Tension increments of mooring lines also changed little with the pretension but increased rapidly when amplitude and layer fluid depth ratio increased.However,FPSO’s motion increased quickly with not only the horizontal pretension but also the amplitude of internal solitary wave and layer fluid depth ratio.
基金This study was financially supported by the National Natural Science Foundation of China(Grant Nos.11802176 and 11802301).
文摘An investigation into the prediction method for internal solitary waves(ISWs)loads on the columns and caissons of the semi-submersible platform found on three kinds of internal solitary wave theories and the modified Morison Equation is described.The characteristics of loads exerted on the semi-submersible platform model caused by the ISWs have been observed experimentally,and the inertial and drag coefficients in Morison Equation are determined by analyzing the forces of experiments.From the results,it is of interest to find that Reynolds number,KC number and layer thickness ratio have a considerable influence on the coefficients.The direction of incoming waves,how-ever,is almost devoid of effects on the coefficients.The drag coefficient of columns varies as an exponential function of Reynolds number,and inertia coefficient of columns is a power function related to KC number.Meanwhile,the drag coefficient of caissons is approximately constant in terms of regression analysis of experimental data.The results from different experimental conditions reveal that the inertia coefficient of caissons appears to be exponential correlated with upper layer depths.
基金Supported by the National Natural Science Foundation of China(Nos.41030855,U1133001,41376027)National High Technology Research and Development Program of China(863 Program)(No.2013AA09A502)
文摘Internal solitary waves （ISWs） are frequently observed in the area between Dongsha Island （DI） and Taiwan Island. However, there have been few in-situ observations southwest of DI. To improve our knowledge of ISWs in this area, we observed the ISWs over the continental shelf （115.4°E, 20.3°N） from Aug. 29 to Oct. 10, 2011 with temperature sensors and an acoustic Doppler current profiler （ADCP）. The observations showed that the a fully developed ISW produced a current whose maximum westward velocity was 0.92 rrds and maximum northward velocity was 0.47 m/s. During the 41-day observation period the ISWs appeared for three periods with about 7-day gaps between each period. During each day, two types of ISWs were observed. The first type of wave arrived regularly diurnally at the same time each day, with a similar pattern to that of the type-a wave identified by Ramp et al. （2004）. The second type arrived about 12 h after the first type and was delayed about 1 hour each day; this wave type was related to the type-b wave. Thus, our observations confirmed that both type-a and type-b waves can reach the area southwest of the DI. Moreover, the waves observed by the mooring propagated toward the directions of 270°-315° clockwise from true north, indicating obvious refraction from uneven topography around DI.
