This study demonstrates the two different Rossby wave train（RWT） patterns related to the developing/decaying upper atmospheric heat source over the Tibetan Plateau（TPUHS） in boreal summer. The results show that th...This study demonstrates the two different Rossby wave train（RWT） patterns related to the developing/decaying upper atmospheric heat source over the Tibetan Plateau（TPUHS） in boreal summer. The results show that the summer TPUHS is dominated by quasi-biweekly variability, particularly from late July to mid-August when the subtropical jet steadily stays to the north of the TP. During the developing period of TPUHS events, the intensifying TPUHS corresponds to an anomalous upper-tropospheric high over the TP, which acts as the main source of a RWT that extends northeastward, via North China, the central Pacific and Alaska, to the northeastern Pacific region. This RWT breaks up while the anomalous high is temporarily replaced by an anomalous low due to the further deepened convective heating around the TPUHS peak. However, this anomalous low, though existing for only three to four days due to the counteracting dynamical effects of the persisting upper/lower divergence/convergence over the TP, acts as a new wave source to connect to an anomalous dynamical high over the Baikal region. Whilst the anomalous low is diminishing rapidly, this Baikal high becomes the main source of a new RWT, which develops eastward over the North Pacific region till around eight days after the TPUHS peak. Nevertheless, the anomaly centers along this decaying-TPUHS-related RWT mostly appear much weaker than those along the previous RWT.Therefore, their impacts on circulation and weather differ considerably from the developing to the decaying period of TPUHS events.展开更多
A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used ...A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.展开更多
This paper. details experiments undertaken in the UK Coastal Research Facility (CRF)at Hy draulies Research (HR), Wallingford, on transformation and run-up of wave trains. The purpose of these experiments is to provid...This paper. details experiments undertaken in the UK Coastal Research Facility (CRF)at Hy draulies Research (HR), Wallingford, on transformation and run-up of wave trains. The purpose of these experiments is to provide verification data for numerical models of wave transformation in shoaling. surf and swash zones. This is the kind of data ih:lt flume experiments are unable to provide, and is collected in the highly controlled environment of CRF where extrinsic factors present in the field are not an issue. The experiments concerning wave trains are undertaken by use of existing wave generation software, and the run-up measurements are made with large experimental run-up gauges.展开更多
This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional l...This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional linear variation the rays of quasi-stationary planetary wave may propagate along oblique lines and if the meridional variability of heat source has second order term the rays show distinct deformation as a great circular route. Additionally, the inhomogeneous distribution may cause lower frequency oscillations in mid- and low-latitudes. The combination of zonal and meridional wave numbers and distributive character of heat source may form an inverse mechanism of variational trend of generized wave energy, reflecting in some degree the physical process of transition between meridional and zonal flow patterns.展开更多
This study examines the wave trains at 500 hPa occurring in East Asian summer by using the Empirical Orthogonal Function (EOF) analysis as a diagnostic tool.The results are summarized as follows: (1) A wave train patt...This study examines the wave trains at 500 hPa occurring in East Asian summer by using the Empirical Orthogonal Function (EOF) analysis as a diagnostic tool.The results are summarized as follows: (1) A wave train pattern (OKJ pattern) originating from the upstream areas of the Sea of Okhotsk to the subtropical regions could display its strong signal in early and middle summer.The OKJ pattern is clearly recognized in the first EOF component in Eurasia.(2) The other wave train pattern originating from the Philippines via Japan to North America (the P-J pattern) shows quite strong signals in the whole summer.Although the P-J pattern is described as the second EOF component around the area from East Asia to Northeast Pacific Ocean,the variance contribution is the same as that of OKJ pattern in the first EOF component.(3) The composite analyses indicate that the OKJ and P-J wave trains could coexist to some extents.展开更多
In real sea states,damage incidents on offshore floating structures are not due to the whole time series of wave elevation characterized as statistical one but due to few extreme waves or wave groups in irregular wave...In real sea states,damage incidents on offshore floating structures are not due to the whole time series of wave elevation characterized as statistical one but due to few extreme waves or wave groups in irregular wave train.So,using CFD tools to precisely simulate predetermined irregular wave train will lay sound basis for understanding the local characteristic of the flow field and impact loads on offshore floating structures when damage incidents occur.In this article,the generation of single extreme wave is investigated in a numerical wave tank.First,experimental irregular wave train is decomposed into certain number of small-amplitude waves.The Fourier series expansion is performed to determine the amplitude and initial phase angle of each wave component.A hydrodynamic transfer function is used to calculate the amplitude of wave-maker motion associated with each wave component.Then superposition is carried out on all of the wave-maker motion components to get the final wave-maker motion.With the wave-maker motion as input,simulation of the single extreme irregular wave train is modeled successfully.Then the method is applied to simulating a much more complicated irregular wave train.Once again main features of the complicated irregular wave train are reproduced compared with experiment carried out in the new deepwater experimental basin at Shanghai Jiao Tong University.In the simulation,dynamic mesh method is enabled to model the piston-type wave-maker,the Volume Of Fluid（VOF） method is employed to capture the free surface and a dissipation zone is introduced to deal with wave reflection.展开更多
Based on the 500-hPa geopotential height, surface air temperature, and China summer rain-belt type data from 1978 to 2002, the spatial spectrum function sets which well represent the variation of large scale atmospher...Based on the 500-hPa geopotential height, surface air temperature, and China summer rain-belt type data from 1978 to 2002, the spatial spectrum function sets which well represent the variation of large scale atmospheric circulations were obtained using the least square method. A mechanism for the interannual variation of the East Asia-Pacific teleconnection （EAP） wave train in early summer was identified with the low-order spectral method and the hypothesis-test method. The results indicate that, when nonlinear wave- wave and wave-flow interactions on large scale are stronger in the inner dynamic process of the atmosphere, there are obvious nonlinear features in the evolution of the atmospheric circulation, and the EAP exhibits a negative-positive-negative （＂- ＋ -＂） spatial distribution in low to high latitudes in early summer. The corresponding EAP index is positive, which leads to a northward shift of the western Pacific subtropical high （WPSH） and the China rain-belt is located in the Huaihe River valley and its north in summer. On the contrary, when nonlinear wave-wave and wave-flow interactions on large scale are weaker, there appears a linear feature in the evolution of the atmospheric circulation, and the EAP shows a positive-negative-positive （＂＋ - ＋＂） spatial distribution in low to high latitudes. The corresponding EAP index is negative, which inhibits the WPSH against moving northward, and the China rain-belt is located in the Huaihe and Yangtze River valleys and their south.展开更多
The synoptic-scale wave train is a dominant pattern of the synoptic variability over the tropical western Pacific and usually affects the extreme weather over South China and Southeast Asia.Whether it could extend its...The synoptic-scale wave train is a dominant pattern of the synoptic variability over the tropical western Pacific and usually affects the extreme weather over South China and Southeast Asia.Whether it could extend its influence and contribute to the Henan extreme rainfall in July 2021 still needs to be unraveled.We found that during the Henan extreme rainfall days a positively synoptic-scale vorticity disturbance dominated Henan province,China,which was embedded in the synoptic-scale wave train that originated from the western North Pacific.Moreover,the propagating pathway of this synoptic-scale wave train located northward and was likely modulated by the latitudinal location change of the monsoon trough over the western North Pacific.A northernmost displacement of the monsoon trough in July 2021(∼23.2°N)would facilitate the synoptic-scale wave train to propagate farther northwestward via shifting the related barotropic conversion northward.Therefore,the synoptic-scale wave train from the tropics could reach Henan,provide the necessary lifting forcing,and supply abundant water vapor associated with the anomalous southerly for the occurrence of Henan extreme rainfall event.The results implicate that the pre-existing synoptic-scale wave train regulated by the location of the monsoon trough may be a potential precursor for heavy rainfalls in northern Central China.展开更多
The change of summertime synoptic-scale wave train(SWT) activity over the western North Pacific(WNP) since1950 was investigated based on the NCEP–NCAR reanalysis data. It is found that the intensity of SWT has a risi...The change of summertime synoptic-scale wave train(SWT) activity over the western North Pacific(WNP) since1950 was investigated based on the NCEP–NCAR reanalysis data. It is found that the intensity of SWT has a rising trend, while its structure and phase propagation characteristics remain unchanged. Environmental factors responsible for the rising trend are investigated. By separating the whole period into three warming phases(P1: 1950–1958, P2:1978–1986, and P3: 2006–2014), we found that even though the vertical velocity shows a rising trend, the background low-level vorticity over the monsoon trough region increases from P1 to P2 but decreases from P2 to P3, and so is the low-level barotropic energy conversion(CK). Thus, just the environmental dynamic factor could not explain the continuous rising SWT trend. On the other hand, thermodynamic factor, such as the sea surface temperature(SST), moisture, and atmospheric instability, shows a clear step-by-step increasing trend. A non-dimensional synoptic activity index(SAI) that combines the dynamic and thermodynamic factors is then proposed. This index well captures the observed long-term trend of the SWT intensity.展开更多
Using three-dimensional, unsteady N-S equations and k-ε turbulence model, the effect of ambient wind on the pressure wave generated by a high-speed train entering a tunnel was studied via numerical simulation. Pressu...Using three-dimensional, unsteady N-S equations and k-ε turbulence model, the effect of ambient wind on the pressure wave generated by a high-speed train entering a tunnel was studied via numerical simulation. Pressure changes of the train surface and tunnel wall were obtained as well as the flow field around the train. Results show that when the train runs downwind, the pressure change is smaller than that generated when there is no wind. When the train runs upwind, the pressure change is larger. The pressure change is more sensitive in the upwind condition than in the downwind condition. Compared with no wind condition, when the wind velocity is 10 m/s and 30 m/s, the pressure amplitude on the train head is reduced by 2.8% and 10.5%, respectively. The wall pressure amplitude at 400 m away from the tunnel entrance is reduced by 2.4% and 13.5%, respectively. When the wind velocity is-10 m/s and-30 m/s, the pressure amplitude on the train head increases by 3.0% and 17.7%, respectively. The wall pressure amplitude at 400 m away from the tunnel entrance increases by 3.6% and 18.6%, respectively. The pressure waveform slightly changes under ambient wind due to the influence of ambient wind on the pressure wave propagation speed.展开更多
The evolution and transition of planar wave trains propagating through defects(obstacles) in an excitable medium are studied. When the frequency of the planar wave trains is increased, three different dynamical regime...The evolution and transition of planar wave trains propagating through defects(obstacles) in an excitable medium are studied. When the frequency of the planar wave trains is increased, three different dynamical regimes,namely fusion, "V" waves, and spiral waves, are observed in turn and the underlying mechanism is discussed. The dynamics is concerned with the shapes of the defects. Circle, triangle, and rectangle defects with different sizes are considered. The increase of pacing frequency broadens the fan-shaped broken region in the behind of a rectangle defect.The increase of width of a triangle defect leads to breakup of wave trains easier while the change of height shows opposite effect, which is presented in a phase diagram. Dynamical comparison on defects with different shapes indicates that the decrease of the defect width along the propagation of wave trains makes the fan-shaped region and the minimal frequency for breakup of spiral both increased.展开更多
Potential tsunami generated in the Okinawa Trench or the Manila Trench may attack the southeast coast of China. The continental shelves with extremely gentle slope in the China Seas affect the evolvement of tsunami wa...Potential tsunami generated in the Okinawa Trench or the Manila Trench may attack the southeast coast of China. The continental shelves with extremely gentle slope in the China Seas affect the evolvement of tsunami waves. In this paper, we carry out the simulation of tsunami propagation based on the fully nonlinear and highly dispersive Boussinesq model, which could describe the nonlinearity and dispersion of water waves quite well. So the undulation characters could be well presented. In terms of the real topographies of the East China Sea and the South China Sea, we take some typical profiles to simulate the hypothetical tsunamis generated in the Okinawa Trench and the Manila Trench. Different waveforms in the near shore regions are obtained. The N-shape tsunami waves will evolve into long wave trains, undular bores or solitons near the coastal area. The numerical results of the near shore waveform provide essential conditions for the further studies of tsunami runup and inundation.展开更多
At 13：46 on March 11, 2011（Beijing time）, an earthquake of Mw=9.0 occurred in Japan. By comparing the tsunami data from Guanhekou marine station with other tsunami wave observation gathered from southeast coastal a...At 13：46 on March 11, 2011（Beijing time）, an earthquake of Mw=9.0 occurred in Japan. By comparing the tsunami data from Guanhekou marine station with other tsunami wave observation gathered from southeast coastal area of China, it was evident that, only in Guanhekou, the position of the maximum wave height appeared in the middle part rather than in the front of the tsunami wave train. A numerical model of tsunami propagation based on 2-D nonlinear shallow water equations was built to study the impact range and main causes of the special tsunami waveform discovered in Jiangsu coastal area. The results showed that nearly three-quarters of the Jiangsu coastal area, mainly comprised the part north of the radial sand ridges, reached its maximum tsunami wave height in the middle part of the wave train. The main cause of the special waveform was the special underwater topography condition of the Yellow Sea and the East China Sea area, which influenced the tsunami propagation and waveform significantly. Although land boundary reflection brought an effect on the position of the maximum wave height to a certain extent, as the limits of the incident waveform and distances between the observation points and shore, it was not the dominant influence factor of the special waveform. Coriolis force＇s impact on the tsunami waves was so weak that it was not the main cause for the special phenomenon in Jiangsu coastal area. The study reminds us that the most destructive wave might not appear in the first one in tsunami wave train.展开更多
基金jointly supported by the National Science Foundation of China(Grant Nos.91437105,41575041 and 41430533)the China Meteorological Administration Special Public Welfare Research Fund(Grant No.GYHY201406001)
文摘This study demonstrates the two different Rossby wave train（RWT） patterns related to the developing/decaying upper atmospheric heat source over the Tibetan Plateau（TPUHS） in boreal summer. The results show that the summer TPUHS is dominated by quasi-biweekly variability, particularly from late July to mid-August when the subtropical jet steadily stays to the north of the TP. During the developing period of TPUHS events, the intensifying TPUHS corresponds to an anomalous upper-tropospheric high over the TP, which acts as the main source of a RWT that extends northeastward, via North China, the central Pacific and Alaska, to the northeastern Pacific region. This RWT breaks up while the anomalous high is temporarily replaced by an anomalous low due to the further deepened convective heating around the TPUHS peak. However, this anomalous low, though existing for only three to four days due to the counteracting dynamical effects of the persisting upper/lower divergence/convergence over the TP, acts as a new wave source to connect to an anomalous dynamical high over the Baikal region. Whilst the anomalous low is diminishing rapidly, this Baikal high becomes the main source of a new RWT, which develops eastward over the North Pacific region till around eight days after the TPUHS peak. Nevertheless, the anomaly centers along this decaying-TPUHS-related RWT mostly appear much weaker than those along the previous RWT.Therefore, their impacts on circulation and weather differ considerably from the developing to the decaying period of TPUHS events.
文摘A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.
基金This project was supported by the Flood and Coastal Defense Commission of UK(FD0204)the National Natural Science Foundation of China(59809001)
文摘This paper. details experiments undertaken in the UK Coastal Research Facility (CRF)at Hy draulies Research (HR), Wallingford, on transformation and run-up of wave trains. The purpose of these experiments is to provide verification data for numerical models of wave transformation in shoaling. surf and swash zones. This is the kind of data ih:lt flume experiments are unable to provide, and is collected in the highly controlled environment of CRF where extrinsic factors present in the field are not an issue. The experiments concerning wave trains are undertaken by use of existing wave generation software, and the run-up measurements are made with large experimental run-up gauges.
文摘This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional linear variation the rays of quasi-stationary planetary wave may propagate along oblique lines and if the meridional variability of heat source has second order term the rays show distinct deformation as a great circular route. Additionally, the inhomogeneous distribution may cause lower frequency oscillations in mid- and low-latitudes. The combination of zonal and meridional wave numbers and distributive character of heat source may form an inverse mechanism of variational trend of generized wave energy, reflecting in some degree the physical process of transition between meridional and zonal flow patterns.
基金China-Japan intergovernmental cooperation program of the JICA (2009LASWZF04)Program of Ministry of Science and Technology of China (2009DFB20540)
文摘This study examines the wave trains at 500 hPa occurring in East Asian summer by using the Empirical Orthogonal Function (EOF) analysis as a diagnostic tool.The results are summarized as follows: (1) A wave train pattern (OKJ pattern) originating from the upstream areas of the Sea of Okhotsk to the subtropical regions could display its strong signal in early and middle summer.The OKJ pattern is clearly recognized in the first EOF component in Eurasia.(2) The other wave train pattern originating from the Philippines via Japan to North America (the P-J pattern) shows quite strong signals in the whole summer.Although the P-J pattern is described as the second EOF component around the area from East Asia to Northeast Pacific Ocean,the variance contribution is the same as that of OKJ pattern in the first EOF component.(3) The composite analyses indicate that the OKJ and P-J wave trains could coexist to some extents.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences [grant number XDA17010105]the National Natural Science Foundation of China [grant numbers 91437105,41430533,and 41575041]the Key Research Program of Frontier Sciences [grant number QYZDY-SSW-DQC018]
基金supported by the National High Technology Research and Development Program of China (863 Program,Grant No. 2006AA09A107)the National Natural Science Foundation of China (Grant No. 50709079)
文摘In real sea states,damage incidents on offshore floating structures are not due to the whole time series of wave elevation characterized as statistical one but due to few extreme waves or wave groups in irregular wave train.So,using CFD tools to precisely simulate predetermined irregular wave train will lay sound basis for understanding the local characteristic of the flow field and impact loads on offshore floating structures when damage incidents occur.In this article,the generation of single extreme wave is investigated in a numerical wave tank.First,experimental irregular wave train is decomposed into certain number of small-amplitude waves.The Fourier series expansion is performed to determine the amplitude and initial phase angle of each wave component.A hydrodynamic transfer function is used to calculate the amplitude of wave-maker motion associated with each wave component.Then superposition is carried out on all of the wave-maker motion components to get the final wave-maker motion.With the wave-maker motion as input,simulation of the single extreme irregular wave train is modeled successfully.Then the method is applied to simulating a much more complicated irregular wave train.Once again main features of the complicated irregular wave train are reproduced compared with experiment carried out in the new deepwater experimental basin at Shanghai Jiao Tong University.In the simulation,dynamic mesh method is enabled to model the piston-type wave-maker,the Volume Of Fluid（VOF） method is employed to capture the free surface and a dissipation zone is introduced to deal with wave reflection.
基金the National Natural Science Foundation of China under Grant Nos.40875054 and U0933603the Natural Science Foundation of Yunnan Province under Grant No.2009CC002.
文摘Based on the 500-hPa geopotential height, surface air temperature, and China summer rain-belt type data from 1978 to 2002, the spatial spectrum function sets which well represent the variation of large scale atmospheric circulations were obtained using the least square method. A mechanism for the interannual variation of the East Asia-Pacific teleconnection （EAP） wave train in early summer was identified with the low-order spectral method and the hypothesis-test method. The results indicate that, when nonlinear wave- wave and wave-flow interactions on large scale are stronger in the inner dynamic process of the atmosphere, there are obvious nonlinear features in the evolution of the atmospheric circulation, and the EAP exhibits a negative-positive-negative （＂- ＋ -＂） spatial distribution in low to high latitudes in early summer. The corresponding EAP index is positive, which leads to a northward shift of the western Pacific subtropical high （WPSH） and the China rain-belt is located in the Huaihe River valley and its north in summer. On the contrary, when nonlinear wave-wave and wave-flow interactions on large scale are weaker, there appears a linear feature in the evolution of the atmospheric circulation, and the EAP shows a positive-negative-positive （＂＋ - ＋＂） spatial distribution in low to high latitudes. The corresponding EAP index is negative, which inhibits the WPSH against moving northward, and the China rain-belt is located in the Huaihe and Yangtze River valleys and their south.
基金National Natural Science Foundation of China(41875087,42030601 and 42105017)Applied Technology Research Fund of CMA·Henan Key Laboratory of Agrometeorological Support and Applied Technique(KQ202160).
文摘The synoptic-scale wave train is a dominant pattern of the synoptic variability over the tropical western Pacific and usually affects the extreme weather over South China and Southeast Asia.Whether it could extend its influence and contribute to the Henan extreme rainfall in July 2021 still needs to be unraveled.We found that during the Henan extreme rainfall days a positively synoptic-scale vorticity disturbance dominated Henan province,China,which was embedded in the synoptic-scale wave train that originated from the western North Pacific.Moreover,the propagating pathway of this synoptic-scale wave train located northward and was likely modulated by the latitudinal location change of the monsoon trough over the western North Pacific.A northernmost displacement of the monsoon trough in July 2021(∼23.2°N)would facilitate the synoptic-scale wave train to propagate farther northwestward via shifting the related barotropic conversion northward.Therefore,the synoptic-scale wave train from the tropics could reach Henan,provide the necessary lifting forcing,and supply abundant water vapor associated with the anomalous southerly for the occurrence of Henan extreme rainfall event.The results implicate that the pre-existing synoptic-scale wave train regulated by the location of the monsoon trough may be a potential precursor for heavy rainfalls in northern Central China.
基金Supported by the National Key Research and Development Program of China(2017YFA0603802)National Natural Science Foundation of China(41630423 and 41875069)+1 种基金US National Oceanic and Atmospheric Adminsitration(NA18OAR4310298)US National Science Foundation(AGS-2006553)。
文摘The change of summertime synoptic-scale wave train(SWT) activity over the western North Pacific(WNP) since1950 was investigated based on the NCEP–NCAR reanalysis data. It is found that the intensity of SWT has a rising trend, while its structure and phase propagation characteristics remain unchanged. Environmental factors responsible for the rising trend are investigated. By separating the whole period into three warming phases(P1: 1950–1958, P2:1978–1986, and P3: 2006–2014), we found that even though the vertical velocity shows a rising trend, the background low-level vorticity over the monsoon trough region increases from P1 to P2 but decreases from P2 to P3, and so is the low-level barotropic energy conversion(CK). Thus, just the environmental dynamic factor could not explain the continuous rising SWT trend. On the other hand, thermodynamic factor, such as the sea surface temperature(SST), moisture, and atmospheric instability, shows a clear step-by-step increasing trend. A non-dimensional synoptic activity index(SAI) that combines the dynamic and thermodynamic factors is then proposed. This index well captures the observed long-term trend of the SWT intensity.
基金Projects(U1134203,51575538)supported by the National Natural Science Foundation of ChinaProject(2014T001-A)supported by the Technological Research and Development Program of China Railways CorporationProject(2015ZZTS210)supported by the Fundamental Research Funds for the Central South Universities of China
文摘Using three-dimensional, unsteady N-S equations and k-ε turbulence model, the effect of ambient wind on the pressure wave generated by a high-speed train entering a tunnel was studied via numerical simulation. Pressure changes of the train surface and tunnel wall were obtained as well as the flow field around the train. Results show that when the train runs downwind, the pressure change is smaller than that generated when there is no wind. When the train runs upwind, the pressure change is larger. The pressure change is more sensitive in the upwind condition than in the downwind condition. Compared with no wind condition, when the wind velocity is 10 m/s and 30 m/s, the pressure amplitude on the train head is reduced by 2.8% and 10.5%, respectively. The wall pressure amplitude at 400 m away from the tunnel entrance is reduced by 2.4% and 13.5%, respectively. When the wind velocity is-10 m/s and-30 m/s, the pressure amplitude on the train head increases by 3.0% and 17.7%, respectively. The wall pressure amplitude at 400 m away from the tunnel entrance increases by 3.6% and 18.6%, respectively. The pressure waveform slightly changes under ambient wind due to the influence of ambient wind on the pressure wave propagation speed.
基金Supported by the Natural Science Foundation of Zhejiang Province under Grant Nos.LQ14A050003 and LR17A050001Zhejiang Province Commonweal Projects under Grant No.GK180906288001China Scholarship Council under Grant No.201708330401
文摘The evolution and transition of planar wave trains propagating through defects(obstacles) in an excitable medium are studied. When the frequency of the planar wave trains is increased, three different dynamical regimes,namely fusion, "V" waves, and spiral waves, are observed in turn and the underlying mechanism is discussed. The dynamics is concerned with the shapes of the defects. Circle, triangle, and rectangle defects with different sizes are considered. The increase of pacing frequency broadens the fan-shaped broken region in the behind of a rectangle defect.The increase of width of a triangle defect leads to breakup of wave trains easier while the change of height shows opposite effect, which is presented in a phase diagram. Dynamical comparison on defects with different shapes indicates that the decrease of the defect width along the propagation of wave trains makes the fan-shaped region and the minimal frequency for breakup of spiral both increased.
基金supported by the National Natural Science Foundation of China (11202130 )the Doctoral Program Foundation of Higher Education (20060248046)
文摘Potential tsunami generated in the Okinawa Trench or the Manila Trench may attack the southeast coast of China. The continental shelves with extremely gentle slope in the China Seas affect the evolvement of tsunami waves. In this paper, we carry out the simulation of tsunami propagation based on the fully nonlinear and highly dispersive Boussinesq model, which could describe the nonlinearity and dispersion of water waves quite well. So the undulation characters could be well presented. In terms of the real topographies of the East China Sea and the South China Sea, we take some typical profiles to simulate the hypothetical tsunamis generated in the Okinawa Trench and the Manila Trench. Different waveforms in the near shore regions are obtained. The N-shape tsunami waves will evolve into long wave trains, undular bores or solitons near the coastal area. The numerical results of the near shore waveform provide essential conditions for the further studies of tsunami runup and inundation.
基金financially supported by the Fundamental Research Funds for the Central Universities,Hohai University(Grant No.2011B06014)the Fundamental Research Funds for the Central Public Welfare Research Institutes,Nanjing Hydraulic Research Institute(Grant No.YN912001)+2 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK2012411)the National Science & Technology Pillar Program(Grant No.2012BAB03B01)the Cultivation of Jiangsu Province Graduate Innovation Project(Grant No.KYZZ_0151)
文摘At 13：46 on March 11, 2011（Beijing time）, an earthquake of Mw=9.0 occurred in Japan. By comparing the tsunami data from Guanhekou marine station with other tsunami wave observation gathered from southeast coastal area of China, it was evident that, only in Guanhekou, the position of the maximum wave height appeared in the middle part rather than in the front of the tsunami wave train. A numerical model of tsunami propagation based on 2-D nonlinear shallow water equations was built to study the impact range and main causes of the special tsunami waveform discovered in Jiangsu coastal area. The results showed that nearly three-quarters of the Jiangsu coastal area, mainly comprised the part north of the radial sand ridges, reached its maximum tsunami wave height in the middle part of the wave train. The main cause of the special waveform was the special underwater topography condition of the Yellow Sea and the East China Sea area, which influenced the tsunami propagation and waveform significantly. Although land boundary reflection brought an effect on the position of the maximum wave height to a certain extent, as the limits of the incident waveform and distances between the observation points and shore, it was not the dominant influence factor of the special waveform. Coriolis force＇s impact on the tsunami waves was so weak that it was not the main cause for the special phenomenon in Jiangsu coastal area. The study reminds us that the most destructive wave might not appear in the first one in tsunami wave train.
