A physical model has been constructed to represent the condensate film pattern on a horizontal downward-facing surface with fins,which is based on visual observation in experiment,The results of analysis using this mo...A physical model has been constructed to represent the condensate film pattern on a horizontal downward-facing surface with fins,which is based on visual observation in experiment,The results of analysis using this model confirums the validity of the critical wave length formula obtained from Rayleigh-Taylor staility analysis .This formula may be used as a criterion to design horzontal downward-facing surfaces with fins that can best destabilize the condensate film,thus enhancing condensation heat transfer.展开更多
We simulated the temporal correlation of sound transmission using a two-dimensional advective frozen-ocean model with temperature data from a temperature sensor array on a propagation path in the South China Sea(SCS) ...We simulated the temporal correlation of sound transmission using a two-dimensional advective frozen-ocean model with temperature data from a temperature sensor array on a propagation path in the South China Sea(SCS) Experiment 2009,and investigated the relationships of temporal correlation length,source-receiver range,and maximal sound speed fluctuation mainly caused by the solitary internal waves.We found that the temporal correlation length is-1.2-power dependent on source-receiver range and-0.9-power dependent on maximal sound speed fluctuation.The empirical relationship is deduced from one-day environmental measurements in a limited area,needing more works and verification in the future with more acoustic data.But the relationship is useful in many applications in the area of SCS Experiment 2009.展开更多
The new distributions of the statistics of wave groups based on the maximum entropy principle are presented. The maximum entropy distributions appear to be superior to conventional distributions when applied to a limi...The new distributions of the statistics of wave groups based on the maximum entropy principle are presented. The maximum entropy distributions appear to be superior to conventional distributions when applied to a limited amount of information. Its applications to the wave group properties show the effectiveness of the maximum entropy distribution. FFF filtering method is employed to obtain the wave envelope fast and efficiently. Comparisons of both the maximum entropy distribution and the distribution of Longuet-Higgins （1984） with the laboratory wind-wave data show that the former gives a better fit.展开更多
According to the mechanism of sediment suspension under waves, namely, the main reason of sediment suspension changes from the turbulent mixing in the bottom boundary layer to the periodic motion of the water particle...According to the mechanism of sediment suspension under waves, namely, the main reason of sediment suspension changes from the turbulent mixing in the bottom boundary layer to the periodic motion of the water particle near the free water surface, a three-layer model of sediment concentration distribution due to waves is presented along the whole water depth based on the concept of the finite mixing length. 1he determination of the parameters in the model is discussed and an empirical formula is suggested. Comparisons between the calculated results and the measurements indicate that the resuits of the model agree well with the data from both the large and small scale flume experiments.展开更多
Three dimensional wave-induced mixing plays an important role in shallow water area. A quite direct approach through the Reynolds average upon characteristic length scale is proposed to parameterize the horizontal and...Three dimensional wave-induced mixing plays an important role in shallow water area. A quite direct approach through the Reynolds average upon characteristic length scale is proposed to parameterize the horizontal and vertical shallow water mixing. Comparison of finite depth case with infinite depth results indicates that the difference of the wave-induced mixing strength is evident. In the shallow water condition, the infinite water depth approximation overestimates the mixing strength in the lower layers. The nonzero horizontal wave-induced mixing presents anisotropic property near the shore. The Prandtl＇s mixing length theory underestimated the wave-induced mixing in the previous studies.展开更多
Wave energy spectrum in shallow water can be studied in wind wave channel in combination with irregular wave- maker. Fetch length is successfully extended and by 'Relay' method the corresponding spectrum patte...Wave energy spectrum in shallow water can be studied in wind wave channel in combination with irregular wave- maker. Fetch length is successfully extended and by 'Relay' method the corresponding spectrum pattern and the wind velocity scale are obtained.展开更多
Ship floating condition in regular waves is calculated. New equations controlling any ship＇s floating condition are proposed by use of the vector operation. This form is a nonlinear optimization problem which can be ...Ship floating condition in regular waves is calculated. New equations controlling any ship＇s floating condition are proposed by use of the vector operation. This form is a nonlinear optimization problem which can be solved using the penalty function method with constant coefficients. And the solving process is accelerated by dichotomy. During the solving process, the ship＇s displacement and buoyant centre have been calculated by the integration of the ship surface according to the waterline. The ship surface is described using an accumulative chord length theory in order to determine the displacement, the buoyancy center and the waterline. The draught forming the waterline at each station can be found out by calculating the intersection of the ship surface and the wave surface. The results of an example indicate that this method is exact and efficient. It can calculate the ship floating condition in regular waves as well as simplify the calculation and improve the computational efficiency and the precision of results.展开更多
The approach to estimate the length of extended targets by using the bistatic high resolution range profile（ H RRP） is analyzed in this paper. The relationship between the bistatic H RRP and the monostatic H RRP of ...The approach to estimate the length of extended targets by using the bistatic high resolution range profile（ H RRP） is analyzed in this paper. The relationship between the bistatic H RRP and the monostatic H RRP of extended targets are investigated. It is demonstrated by simulations that the target length measured by the bistatic H RRP is more meaningful and accurate than that by the monostatic HRRP,though the monostatic H RRP has been well developed and widely used in target recognizing and classification. The estimation results of a cone shaped target are present and compared at the end of the paper. To assure the reliability of the simulation,the bistatic H RRP is obtained through the scattering field data calculated by a fullwave numerical method,FE-BI-MLFMA.展开更多
Correlation lengths of ultra-low-frequency(ULF)waves around Mars were computed for the first time,using data from MEX(electron density from 2004 to 2015)and MAVEN(electron density and magnetic field from 2014 to 2016)...Correlation lengths of ultra-low-frequency(ULF)waves around Mars were computed for the first time,using data from MEX(electron density from 2004 to 2015)and MAVEN(electron density and magnetic field from 2014 to 2016).Analysis of the MEX data found that,for the frequency range 8 to 50 mHz,correlation length in electron density varied between 13 and 17 seconds(temporal scale)and between 5.5×10^3 km and 6.8×10^3 km(spatial scale).For the MAVEN time interval,correlation length was found to vary between 11 and 16 seconds(temporal scale)and 2×10^3–4.5×10^3 km in spatial scale.In the magnetic field data,correlation lengths are observed to be between 8–15 seconds(temporal scale)and between 1×10^3 and 5×10^3 km(spatial scale)over the same frequency range.We observe that the cross sections of the plasma regions at the dayside of Mars are smaller than these correlation lengths in these regions in both analyses,where the correlation length derived from the MEX electron density data was between 5 and 25 times the size of the magnetosheath and the magnetic pile-up region(MPR),respectively.For MAVEN these ratios are about 4(magnetosheath)and 11(MPR)in electron density and between 1.5 and 5.5 for magnetic field data,respectively.These results indicate that waves at the magnetosheath/MPR can be related to oscillations in the upper ionosphere.In a local region,wave trains may cause resonance effects at the planetary ionopause,which consequently contributes to the enhanced ion escape from the atmosphere.展开更多
An experi ment was conducted to measure the breakup lengths of water jets with a high-speed video camera for Weber numbers from0 to about 1.1×103.The initial jet diameters are changed from0.3 mmto 1. 0 mm.The res...An experi ment was conducted to measure the breakup lengths of water jets with a high-speed video camera for Weber numbers from0 to about 1.1×103.The initial jet diameters are changed from0.3 mmto 1. 0 mm.The results indicate that at lowjet velocity the breakup lengths of the jets are increased linearly from 0 to a maxi mumvalue.At the Weber number about 20 the breakup length of the jet reaches its maxi mum value for different initial jet diameter.Acomputation based onthe dispersion equationis conducted to study the relationship between the growth rate of the jet surface wave and the maxi mumbreakup length.The computations showthat the maxi mumgrowth rate for the axisymmetric surface wave has a turning point at Weber number about 20,and that agrees well with the experi ments.展开更多
The basic parameters involved in current start-wave theoretical models such as density and velocity are difficult to obtain through traditional traffic detection devices. Thus it is hard to apply these theoretical mod...The basic parameters involved in current start-wave theoretical models such as density and velocity are difficult to obtain through traditional traffic detection devices. Thus it is hard to apply these theoretical models to the actual verification and prediction for real situation. Unmanned aerial vehicle( UAV),which can shoot aerial video and identify vehicles, roads and other objects, is introduced in this study as a new type of traffic information collection method to gather the real-time data of the necessary parameters. An improved start-wave velocity model is proposed,where the speed and density of traffic flow are converted into vehicle space headway,mean vehicle length and other auxiliary parameters which can be recognized from aerial video or other means. A UAV was used for video shooting at intersections in a flight experiment in order to verify the accuracy of the calculated start-wave velocity.The mean absolute error rate between the calculated velocity and the actual velocity is 2. 277%. Moreover, the improved start-wave velocity model showed much better accuracy than the traditional start-wave velocity model. The results indicate that the improved model is accurate enough to be used for model calibration and validation in signal timing optimization.展开更多
文摘A physical model has been constructed to represent the condensate film pattern on a horizontal downward-facing surface with fins,which is based on visual observation in experiment,The results of analysis using this model confirums the validity of the critical wave length formula obtained from Rayleigh-Taylor staility analysis .This formula may be used as a criterion to design horzontal downward-facing surfaces with fins that can best destabilize the condensate film,thus enhancing condensation heat transfer.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX1-YW-12-02)the National Natural Science Foundation of China (Nos.10974218,10734100)
文摘We simulated the temporal correlation of sound transmission using a two-dimensional advective frozen-ocean model with temperature data from a temperature sensor array on a propagation path in the South China Sea(SCS) Experiment 2009,and investigated the relationships of temporal correlation length,source-receiver range,and maximal sound speed fluctuation mainly caused by the solitary internal waves.We found that the temporal correlation length is-1.2-power dependent on source-receiver range and-0.9-power dependent on maximal sound speed fluctuation.The empirical relationship is deduced from one-day environmental measurements in a limited area,needing more works and verification in the future with more acoustic data.But the relationship is useful in many applications in the area of SCS Experiment 2009.
基金The project supported by Natioual Natural Science Foundation of China under Grant Nos. 1057508 and 10302018 and the Natural Science Foundation of Zhejiang Province of China under Grant No. Y605056The authors would like to thank Prof. Sen-Yue Lou for helpful discussions.
基金This work was financially supported by the National Natural Science Foundation of China (Grant No50479028)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No20060423009)
文摘The new distributions of the statistics of wave groups based on the maximum entropy principle are presented. The maximum entropy distributions appear to be superior to conventional distributions when applied to a limited amount of information. Its applications to the wave group properties show the effectiveness of the maximum entropy distribution. FFF filtering method is employed to obtain the wave envelope fast and efficiently. Comparisons of both the maximum entropy distribution and the distribution of Longuet-Higgins （1984） with the laboratory wind-wave data show that the former gives a better fit.
基金Foundation item： Supported by the National Natural Science Foundation of China under Grant No. 51109032, and the National Natural Science Foundation of China under Grant No. 50921001.
文摘伪椭圆沉箱结构上的不规则的波浪力量的试验性的调查被介绍。不规则的波浪从 1.19 s 与二重要波浪高度，和光谱高峰时期范围基于 Jonswap 光谱被产生到 1.81 s。相对多重沉箱的中心线的事件波浪方向从 0 敢琠敨搠獥慰物漠吗？
基金supported by the National Natural Science Foundation of China (Grant No.50279029)
文摘According to the mechanism of sediment suspension under waves, namely, the main reason of sediment suspension changes from the turbulent mixing in the bottom boundary layer to the periodic motion of the water particle near the free water surface, a three-layer model of sediment concentration distribution due to waves is presented along the whole water depth based on the concept of the finite mixing length. 1he determination of the parameters in the model is discussed and an empirical formula is suggested. Comparisons between the calculated results and the measurements indicate that the resuits of the model agree well with the data from both the large and small scale flume experiments.
基金supported by the national young scientist fund of China under contract under contract No 40206003special fund for fundamental scientific research under contract (No 2007G15)
文摘Three dimensional wave-induced mixing plays an important role in shallow water area. A quite direct approach through the Reynolds average upon characteristic length scale is proposed to parameterize the horizontal and vertical shallow water mixing. Comparison of finite depth case with infinite depth results indicates that the difference of the wave-induced mixing strength is evident. In the shallow water condition, the infinite water depth approximation overestimates the mixing strength in the lower layers. The nonzero horizontal wave-induced mixing presents anisotropic property near the shore. The Prandtl＇s mixing length theory underestimated the wave-induced mixing in the previous studies.
文摘Wave energy spectrum in shallow water can be studied in wind wave channel in combination with irregular wave- maker. Fetch length is successfully extended and by 'Relay' method the corresponding spectrum pattern and the wind velocity scale are obtained.
基金financially supported by the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51321065)the Research Fund of State Key Laboratory of Ocean Engineering of Shanghai Jiao Tong University(Grant No.1104)
文摘Ship floating condition in regular waves is calculated. New equations controlling any ship＇s floating condition are proposed by use of the vector operation. This form is a nonlinear optimization problem which can be solved using the penalty function method with constant coefficients. And the solving process is accelerated by dichotomy. During the solving process, the ship＇s displacement and buoyant centre have been calculated by the integration of the ship surface according to the waterline. The ship surface is described using an accumulative chord length theory in order to determine the displacement, the buoyancy center and the waterline. The draught forming the waterline at each station can be found out by calculating the intersection of the ship surface and the wave surface. The results of an example indicate that this method is exact and efficient. It can calculate the ship floating condition in regular waves as well as simplify the calculation and improve the computational efficiency and the precision of results.
基金Supported by the National Natural Science Fundation of China(61001192)
文摘The approach to estimate the length of extended targets by using the bistatic high resolution range profile（ H RRP） is analyzed in this paper. The relationship between the bistatic H RRP and the monostatic H RRP of extended targets are investigated. It is demonstrated by simulations that the target length measured by the bistatic H RRP is more meaningful and accurate than that by the monostatic HRRP,though the monostatic H RRP has been well developed and widely used in target recognizing and classification. The estimation results of a cone shaped target are present and compared at the end of the paper. To assure the reliability of the simulation,the bistatic H RRP is obtained through the scattering field data calculated by a fullwave numerical method,FE-BI-MLFMA.
基金FAPESP agency for support (projects 2016/10794-2 and 2017/00516-8)FAPESP (2018/21657-1) agencies+1 种基金supported by FAPEG (grant no. 201210267000905)CNPq (grants no. 302330/2015-1),CNPq (project CNPq/PQ 302583/20157)
文摘Correlation lengths of ultra-low-frequency(ULF)waves around Mars were computed for the first time,using data from MEX(electron density from 2004 to 2015)and MAVEN(electron density and magnetic field from 2014 to 2016).Analysis of the MEX data found that,for the frequency range 8 to 50 mHz,correlation length in electron density varied between 13 and 17 seconds(temporal scale)and between 5.5×10^3 km and 6.8×10^3 km(spatial scale).For the MAVEN time interval,correlation length was found to vary between 11 and 16 seconds(temporal scale)and 2×10^3–4.5×10^3 km in spatial scale.In the magnetic field data,correlation lengths are observed to be between 8–15 seconds(temporal scale)and between 1×10^3 and 5×10^3 km(spatial scale)over the same frequency range.We observe that the cross sections of the plasma regions at the dayside of Mars are smaller than these correlation lengths in these regions in both analyses,where the correlation length derived from the MEX electron density data was between 5 and 25 times the size of the magnetosheath and the magnetic pile-up region(MPR),respectively.For MAVEN these ratios are about 4(magnetosheath)and 11(MPR)in electron density and between 1.5 and 5.5 for magnetic field data,respectively.These results indicate that waves at the magnetosheath/MPR can be related to oscillations in the upper ionosphere.In a local region,wave trains may cause resonance effects at the planetary ionopause,which consequently contributes to the enhanced ion escape from the atmosphere.
文摘An experi ment was conducted to measure the breakup lengths of water jets with a high-speed video camera for Weber numbers from0 to about 1.1×103.The initial jet diameters are changed from0.3 mmto 1. 0 mm.The results indicate that at lowjet velocity the breakup lengths of the jets are increased linearly from 0 to a maxi mumvalue.At the Weber number about 20 the breakup length of the jet reaches its maxi mum value for different initial jet diameter.Acomputation based onthe dispersion equationis conducted to study the relationship between the growth rate of the jet surface wave and the maxi mumbreakup length.The computations showthat the maxi mumgrowth rate for the axisymmetric surface wave has a turning point at Weber number about 20,and that agrees well with the experi ments.
基金National High Technology Research and Development Program of China(No.2009AA11Z220)
文摘The basic parameters involved in current start-wave theoretical models such as density and velocity are difficult to obtain through traditional traffic detection devices. Thus it is hard to apply these theoretical models to the actual verification and prediction for real situation. Unmanned aerial vehicle( UAV),which can shoot aerial video and identify vehicles, roads and other objects, is introduced in this study as a new type of traffic information collection method to gather the real-time data of the necessary parameters. An improved start-wave velocity model is proposed,where the speed and density of traffic flow are converted into vehicle space headway,mean vehicle length and other auxiliary parameters which can be recognized from aerial video or other means. A UAV was used for video shooting at intersections in a flight experiment in order to verify the accuracy of the calculated start-wave velocity.The mean absolute error rate between the calculated velocity and the actual velocity is 2. 277%. Moreover, the improved start-wave velocity model showed much better accuracy than the traditional start-wave velocity model. The results indicate that the improved model is accurate enough to be used for model calibration and validation in signal timing optimization.
