The slow wave structure(SWS)of higher-order depressed magnetically insulated transmission line oscillator(HDMILO)is analyzed rigorously,and the electromagnetic field distribution is derived.High-frequency analysis res...The slow wave structure(SWS)of higher-order depressed magnetically insulated transmission line oscillator(HDMILO)is analyzed rigorously,and the electromagnetic field distribution is derived.High-frequency analysis results reveal that the degeneracy of two degenerate HEM!1 modes is removed by the slot in swS plate and the two degenerate modes split into two modes which polarize perpendicularly.Adjusting the azi-muthal position of the slots destroys longitudinal oscillation condition of higher-order modes.展开更多
This paper studies three types of coaxial slow wave structures （SWSs）： （1） with ripples on both the inner and outer conductors; （2） with ripples on the outer conductor and smooth on the inner one; and （3） wit...This paper studies three types of coaxial slow wave structures （SWSs）： （1） with ripples on both the inner and outer conductors; （2） with ripples on the outer conductor and smooth on the inner one; and （3） with ripples on the inner conductor and smooth on the outer one. The frequencies, coupling impedances, time growth rates and beam-wave interaction efficiencies of the three types of coaxial SWSs are obtained by theoretical analysis. Moreover, the relativistic Ccrenkov generators （RCGs） with the three types of coaxial SWSs are simulated with a fully electromagnetic particle- in-cell code, and the results verify the theoretical analysis. It is proved that the RCG with double-rippled coaxial SWS has the highest conversion efficiency and the shortest starting time.展开更多
An efficient numerical simulation technique is introduced to extract the propagation characteristics of a millimeter guided wave structure. The method is based on the application of the Krylov subspace model order red...An efficient numerical simulation technique is introduced to extract the propagation characteristics of a millimeter guided wave structure. The method is based on the application of the Krylov subspace model order reduction technique (Padé via Lanczos) to the compact finite difference frequency domain (FDFD) method. This new technique speeds up the solution by decreasing the originally larger system matrix into one lower order system matrix. Numerical experiments from several millimeter guided wave structures demonstrate the efficiency and accuracy of this algorithm.展开更多
The linear dispersion relation of a trapezoidally corrugated slow wave structure （TCSWS） is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency...The linear dispersion relation of a trapezoidally corrugated slow wave structure （TCSWS） is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency range. The dispersion relation is solved by utilizing the Rayleigh-Fourier method by expressing the radial function in terms of the Fourier series. A highly accurate synthetic technique is also applied to determine the complete dispersion characteristics from experimentally measured resonances （cold test）. Periodic structures resonate at specific frequencies when the terminals are shorted numerical calculation, synthetic technique and cold appropriately. The dispersion characteristics obtained from test are compared, and an excellent agreement is achieved.展开更多
The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and ...The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.展开更多
Backward wave oscillators （BWOs） driven by intense relativistic electron beams are very efficient means of producing high-power microwaves. However, the efficiency of conventional BWO is lower than 30%. An X-band ov...Backward wave oscillators （BWOs） driven by intense relativistic electron beams are very efficient means of producing high-power microwaves. However, the efficiency of conventional BWO is lower than 30%. An X-band oversized BWO with non-uniform slow wave structure is designed to improve RF output characteristics. In particle-in-cell simulation, a high power microwave with a power of 8.0 GW and efficiency of 40% is obtained, compared with that of 30% obtained in a conventional relativistic BWO.展开更多
In many cases of wave structure interactions,three-dimensional models are used to demonstrate real-life complex environ-ments in large domain scales.In the seakeeping context,predicting the motion responses in the int...In many cases of wave structure interactions,three-dimensional models are used to demonstrate real-life complex environ-ments in large domain scales.In the seakeeping context,predicting the motion responses in the interaction of a long body resembling a ship structure with regular waves is crucial and can be challenging.In this work,regular waves interacting with a rigid foating structure were simulated using the open-source code based on the weakly compressible smoothed par-ticle hydrodynamics(WCSPH)method,and optimal parameters were suggested for diferent wave environments.Vertical displacements were computed,and their response amplitude operators(RAOs)were found to be in good agreement with experimental,numerical,and analytical results.Discrepancies of numerical and experimental RAOs tended to increase at low wave frequencies,particularly at amidships and near the bow.In addition,the instantaneous wave contours of the sur-rounding model were examined to reveal the efects of localized waves along the structure and wave dissipation.The results indicated that the motion response from the WCSPH responds well at the highest frequency range(ω>5.235 rad/s).展开更多
A variable separation approach is proposed and extended to the （1＋1）-dimensional physics system. The variable separation solution of （1-F1）-dimensional Ito system is obtained. Some special types of solutions such...A variable separation approach is proposed and extended to the （1＋1）-dimensional physics system. The variable separation solution of （1-F1）-dimensional Ito system is obtained. Some special types of solutions such as non-propagating solitary wave solution, propagating solitary wave solution and looped soliton solution are found by selecting the arbitrary function appropriately.展开更多
The second Madden–Julian Oscillation（MJO）event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011（DYNAMO/CINDY2011）exhibi ted an...The second Madden–Julian Oscillation（MJO）event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011（DYNAMO/CINDY2011）exhibi ted an unusual double rainband structure.Using a wavenumber-frequency spectral filtering method,we unveil that this double rainband structure arises primarily from the Kelvin wave component.The zonal phase speed of the double rainbands is about 7.9 degree per day in the equatorial Indian Ocean,being in the range of convectively coupled Kelvin wave phase speeds.The convection and circulation anomalies associated with the Kelvin wave component are characterized by two anomalous convective cells,with low-level westerly（easterly）and high（low）pressure anomalies to the west（east）of the convective centers,and opposite wind and pressure anomalies in the upper troposphere.Such a zonal wind–pressure phase relationship is consistent with the equatorial free-wave dynamics.While the freeatmospheric circulation was dominated by the first baroclinic mode vertical structure,moisture and vertical motion in the boundary layer led the convection.The convection and circulation structures derived based on the conventional MJO filter show a different characteristic.For example,the phase speed is slower（about 5.9 degree per day）,and there were no double convective branches.This suggests that MJO generally involves multi-scales and it is incomplete to extract its signals by using the conventional filtering technique.展开更多
A numerical study of linear wave scattering over a floating platform has been simulated by an efficient numericalmodel in this letter.The non-hydrostatic model is used to simulate the free surface and the uneven botto...A numerical study of linear wave scattering over a floating platform has been simulated by an efficient numericalmodel in this letter.The non-hydrostatic model is used to simulate the free surface and the uneven bottom.For thesolid body modelling,the immersed boundary method(IBM)is implemented by introducing a virtual boundaryforce into the momentum equations to emulate the boundary conditions.This implementation enhances theability of the model to simulate interactions between waves and floating structures.A numerical case involvingwave interactions with a floating platform is studied to validate the numerical model.By simulating the wavepropagation,the numerical model captures the variation of the wave scattering very well,which verifies theperformance of the numerical model and the robust strategy of the IBM.展开更多
This paper proposes a structure combined by baffle and submerged breakwater （abbreviated to SCBSB in the following texts）. Such a combined structure is conducive to the water exchange in the harbor, and has strong c...This paper proposes a structure combined by baffle and submerged breakwater （abbreviated to SCBSB in the following texts）. Such a combined structure is conducive to the water exchange in the harbor, and has strong capability on wave dissipation. Our paper focuses on the discussion of two typical structures, i.e., the submerged baffle and rectangular breakwater combined with the upper baffle respectively, which are named as SCBSB 1 and SCBSB2 for short. The eigenfunction method corrected by experimental results is used to investigate the wave dissipation characteristics. It shows that the calculated results agree well with the experimental data and the minimum value of the wave transmission coefficient can be obtained when the distance between the front and rear structures is from 1/4 to 1/2 of the incident wave length.展开更多
Based on the matching conditions of different fluid regions, the eigenfunction expansion method is used to develop a theoretical formula for wave reflection in front of the perforated structure with a partially slit f...Based on the matching conditions of different fluid regions, the eigenfunction expansion method is used to develop a theoretical formula for wave reflection in front of the perforated structure with a partially slit front wall. The accuracy of the solution is verified by comparing the numerical results with experimental data. In addition, a new hydraulic design method is developed by derivation of the theoretical formula with respect to the porosity of the slit wall, and the results of this design method is drafted for harbour engineers to use.展开更多
In this paper, a numerical model of 2D weakly compressible smoothed particle hydrodynamics(WCSPH) is developed to simulate the interaction between waves and thin structures. A new color domain particle(CDP)technique i...In this paper, a numerical model of 2D weakly compressible smoothed particle hydrodynamics(WCSPH) is developed to simulate the interaction between waves and thin structures. A new color domain particle(CDP)technique is proposed to overcome difficulties of applying the ghost particle method to thin structures in dealing with solid boundaries. The new technique can deal with zero-thickness structures. To apply this enforcing technique, the computational fluid domain is divided into sub domains, i.e., boundary domains and internal domains. A color value is assigned to each particle, and contains the information of the domains in which the particle belongs to and the particles can interact with. A particle, nearby a thin boundary, is prevented from interacting with particles, which should not interact with on the other side of the structure. It is possible to model thin structures, or the structures with the thickness negligible with this technique. The proposed WCSPH module is validated for a still water tank, divided by a thin plate at the middle section, with different water levels in the subdomains, and is applied to simulate the interaction between regular waves and a perforated vertical plate. Finally, the computation is carried out for waves and submerged twin-horizontal plate interaction. It is shown that the numerical results agree well with experimental data in terms of the pressure distribution, pressure time series and wave transmission.展开更多
Wave absorbing structures have been widely applied in many countries. In the present paper, the wave heights in front of a vertical wave absorbing structure with rubble foundation as well as in the wave chamber of the...Wave absorbing structures have been widely applied in many countries. In the present paper, the wave heights in front of a vertical wave absorbing structure with rubble foundation as well as in the wave chamber of the structure are analysed using an approximative calculation method, and the dissipating effect of the structure is verified. On the basis of the results of regular waves, the relative wave heights of irregular waves in front of the wave absorbing structure as well as in the chamber have also been analysed.展开更多
Tengchong volcanic area is located near the impinging and underthrust margin of India and Eurasia plates. The volcanic activity is closely related to the tectonic environment. The deep structure characteristics are in...Tengchong volcanic area is located near the impinging and underthrust margin of India and Eurasia plates. The volcanic activity is closely related to the tectonic environment. The deep structure characteristics are inferred from the receiver function inversion with the teleseismic records in the paper. The results show that the low velocity zone is influenced by the NE-trending Dayingjiang fault. The S-wave low velocity structure occurs obviously in the southern part of the fault, but unobviously in its northern part. There are low velocity zones in the shallow po-sition, which coincides with the seismicity. It also demonstrates that the low velocity zone is directly related to the thermal activity in the volcanic area. Therefore, we consider that the volcano may be alive again.展开更多
The average upper mantle P wave velocity structure and lateral heterogeneity in the northern part of China and Mongolia are investigated by waveform inversion of broadband body waveform data recorded by CDSN and digit...The average upper mantle P wave velocity structure and lateral heterogeneity in the northern part of China and Mongolia are investigated by waveform inversion of broadband body waveform data recorded by CDSN and digital stations around China. The average model has a low P wave velocity lid (about 7.8～8.0 km·s -1 ) with thickness about 60 km, and two discontinuities with velocity jumps of 0.29 km·s -1 and 0.55 km·s -1 at depth of 410 km and 665 km respectively. In the Jungger basin, the P wave velocity of uppermost mantle is about 7.7 km·s -1 . The lid thickness (90～100 km) and velocity gradient (average gradient is greater than 0.005 5/s) are large. At the depth of 140 km the P wave velocity reaches to 8.2 km·s -1 . Near in Baikal, the lid is about 30 km thick with average P wave velocity of 8.00～8.05 km·s -1 .展开更多
In the backward propagation of acoustic waves, the direction of phase velocity is anti-parallel to that of group velocity. We propose a scheme to manipulate the backward propagation using a periodicM structure. The dy...In the backward propagation of acoustic waves, the direction of phase velocity is anti-parallel to that of group velocity. We propose a scheme to manipulate the backward propagation using a periodicM structure. The dynamic backward propagation process is further experimentally observed. It is demonstrated that the oblique incident plane wave moves backward when it travels through the periodical structure and the backward shift can be controlled within a certain range.展开更多
Extreme waves,owing to their enormous impact energy,wide range of action,and strong destructive capacity,generate considerable impact forces that lead to the vibration and damage of offshore photovoltaic and other mar...Extreme waves,owing to their enormous impact energy,wide range of action,and strong destructive capacity,generate considerable impact forces that lead to the vibration and damage of offshore photovoltaic and other marine structures.The generated cracks when waves impact photovoltaic panels affect their power generation efficiency and service life,but research on wave-impacted elastic photovoltaic panels is still lacking.In this work,a two-way fluid-solid coupling numerical method was used to predict the hydroelastic response of photovoltaic panels under different wave conditions.First,an analysis of the impact loading on the photovoltaic panel was presented,including the normal impact force and peak pressure under different wave conditions.The hydroelastic response of the photovoltaic panel to impact,in terms of the displacement of the photovoltaic panel and the stress of the solar cells,was subsequently analyzed and discussed.Finally,the peak stress in the silicon panels was compared with the mechanical strength of the silicon panels,revealing the cracking risk of the PV panels under different sea states.The results showed that the impact force was the main cause of cracks in the photovoltaic panels,which can easily result in damage caused by stress concentrations at their corners,where the stress in the silicon panels was the largest.The peak stress of the photovoltaic panel under the sea state of Grade 6-1 can reach 78.93 MPa,which exceeds the mechanical strength of silicon panels;therefore,there is a larger risk of internal cracking.展开更多
The localization factor is used to describe the band structures for P wave propagating normally in the nanoscaled nearly periodic layered phononic crystals. The localization factor is calculated by the transfer matrix...The localization factor is used to describe the band structures for P wave propagating normally in the nanoscaled nearly periodic layered phononic crystals. The localization factor is calculated by the transfer matrix method based on the nonlocal elastic continuum theory.Three kinds of nearly periodic arrangements are concerned, i.e., random disorder, quasiperiodicity and defects. The influences of randomly disordered degree of the sub-layer＇s thickness and mass density, the arrangement of quasi-periodicity and the location of defect on the band structures and cut-off frequency are analyzed in detail.展开更多
The existence of a global smooth solution for the initial value problem of generalized Kuramoto-Sivashinsky type equations have been obtained. Similarty siolutions and the structure of the traveling waves solution for...The existence of a global smooth solution for the initial value problem of generalized Kuramoto-Sivashinsky type equations have been obtained. Similarty siolutions and the structure of the traveling waves solution for the generalized KS equations are discussed and analysed by using the qualitative theory of ODE and Lie's infinitesimal transformation respectively.展开更多
文摘The slow wave structure(SWS)of higher-order depressed magnetically insulated transmission line oscillator(HDMILO)is analyzed rigorously,and the electromagnetic field distribution is derived.High-frequency analysis results reveal that the degeneracy of two degenerate HEM!1 modes is removed by the slot in swS plate and the two degenerate modes split into two modes which polarize perpendicularly.Adjusting the azi-muthal position of the slots destroys longitudinal oscillation condition of higher-order modes.
文摘This paper studies three types of coaxial slow wave structures （SWSs）： （1） with ripples on both the inner and outer conductors; （2） with ripples on the outer conductor and smooth on the inner one; and （3） with ripples on the inner conductor and smooth on the outer one. The frequencies, coupling impedances, time growth rates and beam-wave interaction efficiencies of the three types of coaxial SWSs are obtained by theoretical analysis. Moreover, the relativistic Ccrenkov generators （RCGs） with the three types of coaxial SWSs are simulated with a fully electromagnetic particle- in-cell code, and the results verify the theoretical analysis. It is proved that the RCG with double-rippled coaxial SWS has the highest conversion efficiency and the shortest starting time.
文摘An efficient numerical simulation technique is introduced to extract the propagation characteristics of a millimeter guided wave structure. The method is based on the application of the Krylov subspace model order reduction technique (Padé via Lanczos) to the compact finite difference frequency domain (FDFD) method. This new technique speeds up the solution by decreasing the originally larger system matrix into one lower order system matrix. Numerical experiments from several millimeter guided wave structures demonstrate the efficiency and accuracy of this algorithm.
文摘The linear dispersion relation of a trapezoidally corrugated slow wave structure （TCSWS） is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency range. The dispersion relation is solved by utilizing the Rayleigh-Fourier method by expressing the radial function in terms of the Fourier series. A highly accurate synthetic technique is also applied to determine the complete dispersion characteristics from experimentally measured resonances （cold test）. Periodic structures resonate at specific frequencies when the terminals are shorted numerical calculation, synthetic technique and cold appropriately. The dispersion characteristics obtained from test are compared, and an excellent agreement is achieved.
基金supported by the National Natural Science Foundation of China(Nos.U20A2069,62376234 and 123B2037)the Advanced Aero-Power Innovation Workstation,China(No.HKCX2024-01-017)。
文摘The selection of an appropriate basic detonation wave flow field is crucial for improving the performance and geometric design of standing detonation vehicles.This paper employs a detailed chemical reaction model and solves the unsteady axisymmetric Euler equation to study the characteristics of the Axisymmetric Inward Turning Curved Detonation Wave(AIT-CDW)flow field and the parameters affecting the stability of the wave system structure of AIT-CDW flow field.The numerical results demonstrate a radial compression effect in the AIT-CDW flow field.This effect causes the detonation wave to have a shorter initiation length than oblique detonation wave flow field and the detonation wave angle to gradually increase with the flow direction postdetonation.The AIT-CDW flow field is confined space,making it prone to normal detonation waves when the detonation wave reflects from the wall.This phenomenon is detrimental to the stability of the wave system structure in the flow field.It has been observed that increasing the center body radius and decreasing the fuel equivalent ratio can effectively reduce the height of the normal detonation wave or even eliminate it.Additionally,a well-designed generatrix shape of the center body can enhance airflow,reduce choked flow,and promote the stability of the wave structure in the flow field.
文摘Backward wave oscillators （BWOs） driven by intense relativistic electron beams are very efficient means of producing high-power microwaves. However, the efficiency of conventional BWO is lower than 30%. An X-band oversized BWO with non-uniform slow wave structure is designed to improve RF output characteristics. In particle-in-cell simulation, a high power microwave with a power of 8.0 GW and efficiency of 40% is obtained, compared with that of 30% obtained in a conventional relativistic BWO.
基金the Ministry of Higher Education(MOHE)of Malaysia under the Long Term Research Grant Scheme(LRGS)No.LRGS21-001–0005 and LRGS/1/2020/UMT/01/1/4.
文摘In many cases of wave structure interactions,three-dimensional models are used to demonstrate real-life complex environ-ments in large domain scales.In the seakeeping context,predicting the motion responses in the interaction of a long body resembling a ship structure with regular waves is crucial and can be challenging.In this work,regular waves interacting with a rigid foating structure were simulated using the open-source code based on the weakly compressible smoothed par-ticle hydrodynamics(WCSPH)method,and optimal parameters were suggested for diferent wave environments.Vertical displacements were computed,and their response amplitude operators(RAOs)were found to be in good agreement with experimental,numerical,and analytical results.Discrepancies of numerical and experimental RAOs tended to increase at low wave frequencies,particularly at amidships and near the bow.In addition,the instantaneous wave contours of the sur-rounding model were examined to reveal the efects of localized waves along the structure and wave dissipation.The results indicated that the motion response from the WCSPH responds well at the highest frequency range(ω>5.235 rad/s).
文摘A variable separation approach is proposed and extended to the （1＋1）-dimensional physics system. The variable separation solution of （1-F1）-dimensional Ito system is obtained. Some special types of solutions such as non-propagating solitary wave solution, propagating solitary wave solution and looped soliton solution are found by selecting the arbitrary function appropriately.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2015CB453200)National Natural Science Foundation of China(41475084,41630423,41575052,and 41375095)+7 种基金US National Science Foundation(AGS-1643297)US Office of Naval Research(N00014-16-12260)US Naval Research Laboratory(N00173-16-1-G906)Jiangsu Natural Science Foundation Key Project(BK20150062)of ChinaJiangsu Shuang-Chuang Team Fund(R2014SCT001)of ChinaSOEST contribution number 9819IPRC contribution number 1211ESMC number 126
文摘The second Madden–Julian Oscillation（MJO）event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011（DYNAMO/CINDY2011）exhibi ted an unusual double rainband structure.Using a wavenumber-frequency spectral filtering method,we unveil that this double rainband structure arises primarily from the Kelvin wave component.The zonal phase speed of the double rainbands is about 7.9 degree per day in the equatorial Indian Ocean,being in the range of convectively coupled Kelvin wave phase speeds.The convection and circulation anomalies associated with the Kelvin wave component are characterized by two anomalous convective cells,with low-level westerly（easterly）and high（low）pressure anomalies to the west（east）of the convective centers,and opposite wind and pressure anomalies in the upper troposphere.Such a zonal wind–pressure phase relationship is consistent with the equatorial free-wave dynamics.While the freeatmospheric circulation was dominated by the first baroclinic mode vertical structure,moisture and vertical motion in the boundary layer led the convection.The convection and circulation structures derived based on the conventional MJO filter show a different characteristic.For example,the phase speed is slower（about 5.9 degree per day）,and there were no double convective branches.This suggests that MJO generally involves multi-scales and it is incomplete to extract its signals by using the conventional filtering technique.
基金supported by Shanghai 2021“Science and Technology Innovation Action Plan”:Scientific and Technological Projects for Social Development(Grant No.21DZ1202701).
文摘A numerical study of linear wave scattering over a floating platform has been simulated by an efficient numericalmodel in this letter.The non-hydrostatic model is used to simulate the free surface and the uneven bottom.For thesolid body modelling,the immersed boundary method(IBM)is implemented by introducing a virtual boundaryforce into the momentum equations to emulate the boundary conditions.This implementation enhances theability of the model to simulate interactions between waves and floating structures.A numerical case involvingwave interactions with a floating platform is studied to validate the numerical model.By simulating the wavepropagation,the numerical model captures the variation of the wave scattering very well,which verifies theperformance of the numerical model and the robust strategy of the IBM.
基金financially supported by the National Key R&D Program of China(Grant No.2017YFC0405402)
文摘This paper proposes a structure combined by baffle and submerged breakwater （abbreviated to SCBSB in the following texts）. Such a combined structure is conducive to the water exchange in the harbor, and has strong capability on wave dissipation. Our paper focuses on the discussion of two typical structures, i.e., the submerged baffle and rectangular breakwater combined with the upper baffle respectively, which are named as SCBSB 1 and SCBSB2 for short. The eigenfunction method corrected by experimental results is used to investigate the wave dissipation characteristics. It shows that the calculated results agree well with the experimental data and the minimum value of the wave transmission coefficient can be obtained when the distance between the front and rear structures is from 1/4 to 1/2 of the incident wave length.
文摘Based on the matching conditions of different fluid regions, the eigenfunction expansion method is used to develop a theoretical formula for wave reflection in front of the perforated structure with a partially slit front wall. The accuracy of the solution is verified by comparing the numerical results with experimental data. In addition, a new hydraulic design method is developed by derivation of the theoretical formula with respect to the porosity of the slit wall, and the results of this design method is drafted for harbour engineers to use.
基金financially supported by the National Research and Development Program of China(Grant No.2016YFC1401405)the National Natural Science Foundation of China(Grant No.51779038)the Public Science and Technology Research Funds Projects of Ocean(Grant No.201405025-1)
文摘In this paper, a numerical model of 2D weakly compressible smoothed particle hydrodynamics(WCSPH) is developed to simulate the interaction between waves and thin structures. A new color domain particle(CDP)technique is proposed to overcome difficulties of applying the ghost particle method to thin structures in dealing with solid boundaries. The new technique can deal with zero-thickness structures. To apply this enforcing technique, the computational fluid domain is divided into sub domains, i.e., boundary domains and internal domains. A color value is assigned to each particle, and contains the information of the domains in which the particle belongs to and the particles can interact with. A particle, nearby a thin boundary, is prevented from interacting with particles, which should not interact with on the other side of the structure. It is possible to model thin structures, or the structures with the thickness negligible with this technique. The proposed WCSPH module is validated for a still water tank, divided by a thin plate at the middle section, with different water levels in the subdomains, and is applied to simulate the interaction between regular waves and a perforated vertical plate. Finally, the computation is carried out for waves and submerged twin-horizontal plate interaction. It is shown that the numerical results agree well with experimental data in terms of the pressure distribution, pressure time series and wave transmission.
文摘Wave absorbing structures have been widely applied in many countries. In the present paper, the wave heights in front of a vertical wave absorbing structure with rubble foundation as well as in the wave chamber of the structure are analysed using an approximative calculation method, and the dissipating effect of the structure is verified. On the basis of the results of regular waves, the relative wave heights of irregular waves in front of the wave absorbing structure as well as in the chamber have also been analysed.
文摘Tengchong volcanic area is located near the impinging and underthrust margin of India and Eurasia plates. The volcanic activity is closely related to the tectonic environment. The deep structure characteristics are inferred from the receiver function inversion with the teleseismic records in the paper. The results show that the low velocity zone is influenced by the NE-trending Dayingjiang fault. The S-wave low velocity structure occurs obviously in the southern part of the fault, but unobviously in its northern part. There are low velocity zones in the shallow po-sition, which coincides with the seismicity. It also demonstrates that the low velocity zone is directly related to the thermal activity in the volcanic area. Therefore, we consider that the volcano may be alive again.
文摘The average upper mantle P wave velocity structure and lateral heterogeneity in the northern part of China and Mongolia are investigated by waveform inversion of broadband body waveform data recorded by CDSN and digital stations around China. The average model has a low P wave velocity lid (about 7.8～8.0 km·s -1 ) with thickness about 60 km, and two discontinuities with velocity jumps of 0.29 km·s -1 and 0.55 km·s -1 at depth of 410 km and 665 km respectively. In the Jungger basin, the P wave velocity of uppermost mantle is about 7.7 km·s -1 . The lid thickness (90～100 km) and velocity gradient (average gradient is greater than 0.005 5/s) are large. At the depth of 140 km the P wave velocity reaches to 8.2 km·s -1 . Near in Baikal, the lid is about 30 km thick with average P wave velocity of 8.00～8.05 km·s -1 .
基金Supported by the National Natural Science Foundation of China under Grant Nos 11404245 and 11374231the National High-Tech Research and Development Program of China under Grant No 2012AA022606+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20130091130004the National Key Scientific Instrument and Equipment Development Project of China under Grant No 2012YQ15021306
文摘In the backward propagation of acoustic waves, the direction of phase velocity is anti-parallel to that of group velocity. We propose a scheme to manipulate the backward propagation using a periodicM structure. The dynamic backward propagation process is further experimentally observed. It is demonstrated that the oblique incident plane wave moves backward when it travels through the periodical structure and the backward shift can be controlled within a certain range.
基金financially supported by the National Natural Science Foundation of China(Grant No.52371265).
文摘Extreme waves,owing to their enormous impact energy,wide range of action,and strong destructive capacity,generate considerable impact forces that lead to the vibration and damage of offshore photovoltaic and other marine structures.The generated cracks when waves impact photovoltaic panels affect their power generation efficiency and service life,but research on wave-impacted elastic photovoltaic panels is still lacking.In this work,a two-way fluid-solid coupling numerical method was used to predict the hydroelastic response of photovoltaic panels under different wave conditions.First,an analysis of the impact loading on the photovoltaic panel was presented,including the normal impact force and peak pressure under different wave conditions.The hydroelastic response of the photovoltaic panel to impact,in terms of the displacement of the photovoltaic panel and the stress of the solar cells,was subsequently analyzed and discussed.Finally,the peak stress in the silicon panels was compared with the mechanical strength of the silicon panels,revealing the cracking risk of the PV panels under different sea states.The results showed that the impact force was the main cause of cracks in the photovoltaic panels,which can easily result in damage caused by stress concentrations at their corners,where the stress in the silicon panels was the largest.The peak stress of the photovoltaic panel under the sea state of Grade 6-1 can reach 78.93 MPa,which exceeds the mechanical strength of silicon panels;therefore,there is a larger risk of internal cracking.
基金support by the National Science Foundation under Grant no. 11272043
文摘The localization factor is used to describe the band structures for P wave propagating normally in the nanoscaled nearly periodic layered phononic crystals. The localization factor is calculated by the transfer matrix method based on the nonlocal elastic continuum theory.Three kinds of nearly periodic arrangements are concerned, i.e., random disorder, quasiperiodicity and defects. The influences of randomly disordered degree of the sub-layer＇s thickness and mass density, the arrangement of quasi-periodicity and the location of defect on the band structures and cut-off frequency are analyzed in detail.
文摘The existence of a global smooth solution for the initial value problem of generalized Kuramoto-Sivashinsky type equations have been obtained. Similarty siolutions and the structure of the traveling waves solution for the generalized KS equations are discussed and analysed by using the qualitative theory of ODE and Lie's infinitesimal transformation respectively.
