The aim of the present study is to design a new fifth order system of Emden–Fowler equations and related four types of the model.The standard second order form of the Emden–Fowler has been used to obtain the new mod...The aim of the present study is to design a new fifth order system of Emden–Fowler equations and related four types of the model.The standard second order form of the Emden–Fowler has been used to obtain the new model.The shape factor that appear more than one time discussed in detail for every case of the designed model.The singularity atη=0 at one point or multiple points is also discussed at each type of the model.For validation and correctness of the new designed model,one example of each type based on system of fifth order Emden–Fowler equations are provided and numerical solutions of the designed equations of each type have been obtained by using variational iteration scheme.The comparison of the exact results and present numerical outcomes for solving one problem of each type is presented to check the accuracy of the designed model.展开更多
It has been evidenced that shallow gas hydrate resources are abundant in deep oceans worldwide.Their geological back-ground,occurrence,and other characteristics differ significantly from deep-seated hydrates.Because o...It has been evidenced that shallow gas hydrate resources are abundant in deep oceans worldwide.Their geological back-ground,occurrence,and other characteristics differ significantly from deep-seated hydrates.Because of the high risk of well construction and low production efficiency,they are difficult to be recovered by using conventional oil production methods.As a result,this paper proposes an alternative design based on a combination of radial drilling,heat injection,and backfilling methods.Multi-branch holes are used to penetrate shallow gas hydrate reservoirs to expand the depressurization area,and heat injection is utilized as a supplement to improve gas production.Geotechnical information collected from an investigation site close to the offshore production well in the South China Sea is used to assess the essential components of this plan,including well construction stability and gas production behavior.It demonstrates that the hydraulic fracturing of the 60mbsf overburden layer can be prevented by regulating the drilling fluid densities.However,the traditional well structure is unstable,and the suction anchor is advised for better mechanical performance.The gas produc-tion rate can be significantly increased by combining hot water injection and depressurization methods.Additionally,the suitable produc-tion equipment already in use is discussed.展开更多
Due to global warming, the general circulation, underlying surfaces characteristics, and geophysical and meteorological elements all show evident secular trends. This paper points out that when calculating the correla...Due to global warming, the general circulation, underlying surfaces characteristics, and geophysical and meteorological elements all show evident secular trends. This paper points out that when calculating the correlation of two variables containing their own obvious secular trends, the interannual correlation characteristics between the two variables may be distorted （overestimated or underestimated）. Numerical experiments in this paper show that if two variables have opposite secular trends, the correlation coefficient between the two variables is reduced （the positive correlation is underestimated, or the negative correlation is overestimated）; and if the two variables have the same sign of secular trends, the correlation coefficient between the two variables is increased （the positive correlation is overestimated, or the negative correlation is underestimated）. Numerical experiments also suggest that the effect of secular trends on the interannual correlation of the two variables is interchangeable, that is to say, as long as the values of the two trends are not changed, the two variables interchange their positions, and the effect of the secular trends on the interannual correlation coefficient of the two variables remains the same. If the two variables have the same-（opposite-） sign trends, the effect of secular trends on the interannal correlation coefficient is more （less） distinctive. A meteorological example is given.展开更多
In this paper, the summer climate of 1991 in North China is simulated by using the high-resolution regional climate model (RegCM2) and the effects of the grassland desertification on summer drought in the central and ...In this paper, the summer climate of 1991 in North China is simulated by using the high-resolution regional climate model (RegCM2) and the effects of the grassland desertification on summer drought in the central and the northern parts of North China as well as Mongolia are studied. It shows that the regional climate model essentially catches the characteristics on distribution and seasonal variation of the precipitation that keep good agreement with the observation. The desertification makes precipitation in the central part of North China during its flood period decrease obviously in July. The border of the precipitation or the soil moisture reduction in the desertification region extends about one latitude southeastward and beyond the southeast edge of the desertification. Thus, vegetation in the border region approaches desertification further. However, there appears evident difference of variation of precipitation over the whole desertification region. The grassland desertification greatly changes the transfers of fluxes between land and atmosphere. The secondary circulation or secondary circulation cells in the desertification region are excited and as a result moisture transport is changed. The variation of flux transfers between land and atmosphere as well as the vertical motion of atmosphere is closely related to that of precipitation.展开更多
Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version ie (BOZ) and the other B1Z based on B0Z and heterogeneously-treated by' combined approach' , were co 'pled to the m...Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version ie (BOZ) and the other B1Z based on B0Z and heterogeneously-treated by' combined approach' , were co 'pled to the meso-scale model MM4, respectively. Through the calculations of equations from the companion paper, parameters representing land surface heterogeneity and suitable for the coupling models were found out. Three cases were simulated for heavy rainfalls during 36 hours, and the sensitivity of short-term weather modeling to the land surface heterogeneity was tested. Through the analysis of the simulations of the three heavy rainfalls, it was demonstrated that BIZ, compared with BOZ, could more realistically reflect the features of the land surface heterogeneity, therefore could more realistically reproduce the circulation and precipitation amount in the heavy rainfall processes of the three cases. This shows that even short-term weather is sensitive to the land surface heterogeneity, which is more obvious with time passing, and whose influence is more pronounced in the lower layer and gradually extends to the middle and upper layer. Through the analysis of these simulations with BlZ, it is suggested that the bulk effect of smaller-scale fluxes (i.e., the momentum, water vapor and sensible heat fluxes) near the s ig nificantly-heterogeneous land surface is to change the larger-scale (i.e., meso-scale) circulation, and then to influence the development of the low-level jets and precipitation. And also, the complexity of the land-atmosphere interaction was shown in these simulations.展开更多
A finite difference model for solving Navier Stokes viscous liquid sloshing-wave interaction with baffles in a tank. equations with turbulence taken into accotmt is used to investigate The volume-of-fluid and virtual ...A finite difference model for solving Navier Stokes viscous liquid sloshing-wave interaction with baffles in a tank. equations with turbulence taken into accotmt is used to investigate The volume-of-fluid and virtual boundary force methods are employed to simulate free surface flow interaction with structures. A liquid sloshing experimental apparatus was established to evaluate the accuracy of the proposed model, as well as to study nonlinear sloshing in a prismatic tank with the baffles. Damping effects of sloshing in a rectangular tank with bottom-mounted vertical baffles and vertical baffles touching the free surface are studied numerically and experimentally. Good agreement is obtained between the present numerical results and experimental data. The numerical results match well with the current experimental data for strong nonlinear sloshing with large free surface slopes. The reduction in sloshing-wave elevation and impact pressure induced by the bottom-mounted vertical baffle and the vertical baffle touching the free surface is estimated by varying the external excitation frequency and the location and height of the vertical baffle under horizontal excitation.展开更多
A method based on Giorgi (1997a, 1997b) and referred to as ’ combined approach’, which is a combi-nation of mosaic approach and analytical-statistical-dynamical approach, is proposed. Compared with those of other ap...A method based on Giorgi (1997a, 1997b) and referred to as ’ combined approach’, which is a combi-nation of mosaic approach and analytical-statistical-dynamical approach, is proposed. Compared with those of other approaches, the main advantage of the combined approach is that it not only can represent both interpatch and intrapatch variability, but also cost less computational time when the land surface heterogeneity is considered. Because the independent variable of probability density function (PDF) is ex-tended to the single valued function of basic meteorological characteristic quantities, which is much more universal, the analytical expressions of the characteristic quantities (e.g., drag coefficient, snow coverage, leaf surface aerodynamical resistance) affected by roughness length are derived , when the roughness length(and / or the zero plane displacement) heterogeneity has been mainly taken into account with the approach. On the basis of the rule which the PDF parameters should follow, we choose a function y of the roughness length z 0 as the PDF independent variable, and set different values of the two parameters width ratio αn and height ratio γ of PDF (here a linear, symmetric PDF is applied) for sensitivity experiments, from which some conclusions can be drawn, e.g., relevant characteristic terms show different sensitivities to the heterogeneous characteristic (i.e., roughness length), which suggests that we should consider the heterogeneities of the more sensitive terms in our model instead of the heterogeneities of the rest, and which also implies that when the land surface scheme is coupled into the global or regional atmospheric model, sensitivity tests against the distribution of the heterogeneous characteristic are very necessary; when the parameter αn is close to zero, little heterogeneity is represented, and αn differs with cases, which have an upper limit of about 0.6; in the reasonable range of αn, a peak-like distribution of roughness length can be depicted by a small value of γ, etc.. Key words Representation of land surface heterogeneity - “ Combined approach” - Numerical experiment This work was supported by the National Sciences Foundation of China, Grant No.49875005 and the State Key Project (973) G19990434 (03).展开更多
This paper further explores the estimating and expressing of dynamic balance constraints using statistical methods in GRAPES-3DVAR(Version GM). Unlike the single-level scheme which only considers the coupling between ...This paper further explores the estimating and expressing of dynamic balance constraints using statistical methods in GRAPES-3DVAR(Version GM). Unlike the single-level scheme which only considers the coupling between mass and wind at one level, the multi-level scheme considers the coupling between their vertical profiles and calculates the balanced mass field at each layer using the rotational wind at all model levels. A reformed ridge regression method is used in the new scheme to avoid the multicollinearity problem and reduce the noises caused by unbalanced mesoscale disturbances. The results of numerical experiments show that the new scheme can get more reasonable vertical mass field, reduce the magnitude of the adjustment by the initialization, and improve the potential temperature analysis performance. Furthermore, the results of forecast verification in January(winter) and July(summer) both confirm that the new scheme can significantly improve the temperature forecast accuracy and bring slight positive effects to the pressure and wind forecast.展开更多
This paper puts forward a new rock fragmentation loading method of dual-cutter head combined dynamic and static loads. By applying the numerical simulation software - RFPA2D, we have done numerical experiment about th...This paper puts forward a new rock fragmentation loading method of dual-cutter head combined dynamic and static loads. By applying the numerical simulation software - RFPA2D, we have done numerical experiment about the sihstone＇ s crushing effect by dynamic load on single cutter head without confining pressure, dynamic load on single cut- ter head with confining pressure 10 MPa and different dual-cutter heads spacing by combined dynamic and static loads with confining pressure 10 MPa. Experimental results show that the confining pressure can obviously affect the rock frag- mentation effect. Combined dynamic and static loads can greatly improve the rock fragmentation effect. There exists an optimal spacing of dual-cutter head that can make the rock fragmentation achieve the desired effect. Through analyzing the acoustic emission accumulative energy and quantity, the authors make a conclusion that the optimum spacing is 30 mm.展开更多
Tropical cyclones(TCs) Lionrock,Kompasu,and Namtheun were formed successively within 40 hours in 2010.Over the next several days afterwards,these TCs exhibited unusual movements which made operational prediction diffi...Tropical cyclones(TCs) Lionrock,Kompasu,and Namtheun were formed successively within 40 hours in 2010.Over the next several days afterwards,these TCs exhibited unusual movements which made operational prediction difficult.Verifications are performed on the forecasts of the tracks of these TCs with six operational models,including three global and three regional models.Results showed that the trends of TC tracks could be reproduced by these models,whereas trajectory turning points and landfall locations were not simulated effectively.The special track of Lionrock should be associated with its direct interaction with Namtheun,according to a conceptual model of binary TC interaction.By contrast,the relation between Kompasu and Namtheun satisfied the criteria for a semi-direct interaction.Numerical experiments based on the Global and Regional Assimilation and Prediction System-Tropical Cyclone forecast Model(GRAPES-TCM) further confirmed the effect of Namtheun on the unusual tracks of Lionrock and Kompasu.Finally,the physical mechanism of binary TC interaction was preliminarily proposed.展开更多
In order to improve and enhance the numerical modeling methods and its application on debris flow problems,a preliminary study has been proposed in accordance with the corrected water-sediment numerical model on the p...In order to improve and enhance the numerical modeling methods and its application on debris flow problems,a preliminary study has been proposed in accordance with the corrected water-sediment numerical model on the premise of revised resistance and sediment capacity equations.Firstly,an overview the recent re- search achievements on numerical simulation of debris flow has been conducted,the results shown that a gener- al numerical model for debris flow can not be existed at all because the complex rheol...展开更多
A new remote sensing method is described to determine the vertical distribution and total content of atmospheric ozone. The method combines surface infrared, satellite infrared and ultraviolet channels. The width of t...A new remote sensing method is described to determine the vertical distribution and total content of atmospheric ozone. The method combines surface infrared, satellite infrared and ultraviolet channels. The width of the infrared channels is 0.01 cm-1, less than Lorentz half-width at the earth's surface, rather than the present width, because these channels can obtain information about variations in the ozone profile below the profile main-peak. The numerical experiments show that the method has a satisfactory precision in determining total ozone content, just about I percent error, and vertical distribution from the earth to 65 km space. In addition, some semi-analysis functions lor calculating backscattered ultraviolet and a relaxation equation are described in this paper.展开更多
This research applies experimental measurements and NUBEAM,ONETWO and TRANSP modules to investigate the shine-through(ST)loss ratio and beam heating percentage of neutral beam injection on EAST.Measurements and simula...This research applies experimental measurements and NUBEAM,ONETWO and TRANSP modules to investigate the shine-through(ST)loss ratio and beam heating percentage of neutral beam injection on EAST.Measurements and simulations confirm that the ST loss ratio increases linearly with beam energy,and decreases exponentially with plasma density.Moreover,using the multi-step fitting method,we present analytical quantitative expressions of ST loss ratio and beam heating percentage,which are valuable for the high parameter long-pulse experiments of EAST.展开更多
As is known, high-level radioactive waste （HLW） is commonly heat-emitting. Heat output from HLWwilldissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical（THMC） processes. In hi...As is known, high-level radioactive waste （HLW） is commonly heat-emitting. Heat output from HLWwilldissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical（THMC） processes. In highly consolidated clayey rocks, thermal effects are particularly significantbecause of their very low permeability and water-saturated state. Thermal impact on the integrity of thegeological barriers is of most importance with regard to the long-term safety of repositories. This studyfocuses on numerical analysis of thermal effects on hydro-mechanical properties of clayey rock using acoupled thermo-mechanical multiphase flow （TH2M） model which is implemented in the finite elementprogramme OpenGeoSys （OGS）. The material properties of the numerical model are characterised by atransversal isotropic elastic model based on Hooke＇s law, a non-isothermal multiphase flow model basedon van Genuchten function and Darcy＇s law, and a transversal isotropic heat transport model based onFourier＇s law. In the numerical approaches, special attention has been paid to the thermal expansion ofthree different phases： gas, fluid and solid, which could induce changes in pore pressure and porosity.Furthermore, the strong swelling and shrinkage behaviours of clayey material are also considered in thepresent model. The model has been applied to simulate a laboratory heating experiment on claystone.The numerical model gives a satisfactory representation of the observed material behaviour in thelaboratory experiment. The comparison of the calculated results with the laboratory findings verifies thatthe simulation with the present numerical model could provide a deeper understanding of the observedeffects. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
Vertical axis tidal current turbine is a promising device to extract energy from ocean current. One of the important components of the turbine is the connecting arm, which can bring about a significant effect on the p...Vertical axis tidal current turbine is a promising device to extract energy from ocean current. One of the important components of the turbine is the connecting arm, which can bring about a significant effect on the pressure distribution along the span of the turbine blade, herein we call it 3D effect. However, so far the effect is rarely reported in the research, moreover, in numerical simulation. In the present study, a 3D numerical model of the turbine with the connecting arm was developed by using FLUENT software compiling the UDF（User Defined Function） command. The simulation results show that the pressure distribution along the span of blade with the connecting arm model is significantly different from those without the connecting arm. To facilitate the validation of numerical model, the laboratory experiment has been carried out by using three different types of NACA aerofoil connecting arm and circle section connecting arm. And results show that the turbine with NACA0012 connecting arm has the best start-up performance which is 0.346 m/s and the peak point of power conversion coefficient is around 0.33. A further study has been performed and a conclusion is drawn that the aerofoil and thickness of connecting arm are the most important factors on the power conversion coefficient of the vertical axis tidal current turbine.展开更多
In this paper, based on heavy rain numerical forecast model AREM(Advanced Regional Eta Model), two different initialization schemes, LAPS and GRAPES-3DVAR, are used to run assimilation experiments of AREM-LAPS and ARE...In this paper, based on heavy rain numerical forecast model AREM(Advanced Regional Eta Model), two different initialization schemes, LAPS and GRAPES-3DVAR, are used to run assimilation experiments of AREM-LAPS and AREM-3DVAR with the same data source(NCEP forecast field, surface data and radio-soundings) during the period from 21 May to 30 July 2008 to investigate the effect of the two initialization schemes on the rainfall simulation. The result suggests that:(1) the forecast TS score by the AREM-LAPS is higher than that by the AREM-3DVAR for rainfall in different areas, at different valid time and with different intensity, especially for the heavy rain, rainstorm and extremely heavy rain;(2) the AREM-3DVAR can generally simulate the average rainfall distribution, but the forecast area is smaller and rainfall intensity is weaker than the observation, while the AREM-LAPS significantly improves the forecast;(3) the AREM-LAPS gives a better forecast for the south-north shift of rainfall bands and the rainfall intensity variation than the AREM-3DVAR;(4) the AREM-LAPS can give a better reproduction for the daily change in the mean-rainfall-rate of the main rain band, and rainfall intensity changes in the eastern part of Southwest China, the coastal area in South China, the middle-lower valleys of Yangtze river, the Valleys of Huaihe river, and Shandong peninsula, with the rainfall intensity roughly close to the observation, while the rainfall intensity simulated by the AREM-3DVAR is clearly weaker than the observation, especially in the eastern part of Southwest China; and(5) the comparison verification between the AREM-LAPS and AREM-3DVAR for more than 10 typical rainfall processes in the summer of 2008 indicates that the AREM-LAPS gives a much better forecast than AREM-3DVAR in rain-band area, rainfall location and intensity, and in particular, the rainfall intensity forecast is improved obviously.展开更多
The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.Th...The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM.The monsoon indexes for East Asian summer monsoon and land-sea thermal difference,which characterize the intensity of the EASM,show an obvious increase during the onset period of the EASM.Moreover,the land-sea thermal difference is more sensitive to warmer SST.Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China,South China Sea,and the Western Pacific Ocean to the east of the Philippines.While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China,precipitation increases notably in northern China,the South China Sea,the East China Sea,the Yellow Sea,and the Western Pacific to the east of the Philippines.North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent.The surface air temperature shows a warming trend.The warming in the entire troposphere between 30oN and 50oN increases the land-sea thermal contrast,which plays an important role in the enhancement of the EASM.Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension.展开更多
This paper proposed several new types of finite-difference methods for the shallow water equation in absolute coordinate system and put forward an effective two-step predictor-corrector method, a compact and iterative...This paper proposed several new types of finite-difference methods for the shallow water equation in absolute coordinate system and put forward an effective two-step predictor-corrector method, a compact and iterative algorithm for five diagonal matrix. Then the iterative method was used for a multi-grid procedure for shallow water equation. A t last, an initial-boundary value problem was considered, and the numerical results show that the linear sinusoidal wave would successively evolve into conoidal wave.展开更多
In this paper,the effect of water and air fluids on the behavior of a planing catamaran in calm water was studied separately in calm water by using experimental and numerical methods.Experiments were conducted in a to...In this paper,the effect of water and air fluids on the behavior of a planing catamaran in calm water was studied separately in calm water by using experimental and numerical methods.Experiments were conducted in a towing tank over the Froude number range of 0.49–2.9 with two degrees of freedom.The model vessel displacement of 5.3 kg was implemented in experimental tests.Craft behavior was evaluated at the displacements of 5.3,4.6,and 4 kg by using the numerical method.The numerical simulation results for the hull’s resistance force were validated with similar experimental data.The fluid volume model was applied to simulate two-phase flow.The SST k-ωturbulence model was used to investigate the effect of turbulence on the catamaran.The results showed that in the planing mode,the contribution of air to pressure resistance increased by 55%,40%,and 60%at the mentioned displacements,whereas the contribution of air to friction resistance was less than 15%on average.The contribution of the air to the total lift force at the abovementioned displacements exceeded 70%,60%,and 50%in the planing mode but was less than 10%in the displacement mode.At the displacements of 5.3 and 4 kg,the area under the effect of maximum pressure moved around the center of gravity and caused porpoising longitudinal instability at the Froude numbers of 2.9 and 2.4,respectively.However,at the displacement of 4.6 kg,this effect did not occur,and the vessel maintained its stability.展开更多
A numerical experiment on the formation and decay process of a mesolow on the plain east to the Taihang Mountains has been conducted. The dynamical effect of the special topography of the Taihang Mountains and the Yan...A numerical experiment on the formation and decay process of a mesolow on the plain east to the Taihang Mountains has been conducted. The dynamical effect of the special topography of the Taihang Mountains and the Yanshan Mountains on the formation of the mesolow is very important. Namely, the difference of the heating between the Taihang Mountains and the North China plain plays an important role in the formation and decay of the mesolow.展开更多
文摘The aim of the present study is to design a new fifth order system of Emden–Fowler equations and related four types of the model.The standard second order form of the Emden–Fowler has been used to obtain the new model.The shape factor that appear more than one time discussed in detail for every case of the designed model.The singularity atη=0 at one point or multiple points is also discussed at each type of the model.For validation and correctness of the new designed model,one example of each type based on system of fifth order Emden–Fowler equations are provided and numerical solutions of the designed equations of each type have been obtained by using variational iteration scheme.The comparison of the exact results and present numerical outcomes for solving one problem of each type is presented to check the accuracy of the designed model.
基金financially supported by the Natural Science Foundation of Shandong Province(No.ZR202011030013)the National Natural Science Foundation of China(No.41976205)+1 种基金the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2021QNLM020002)the China Geological Survey Program(No.DD20221704).
文摘It has been evidenced that shallow gas hydrate resources are abundant in deep oceans worldwide.Their geological back-ground,occurrence,and other characteristics differ significantly from deep-seated hydrates.Because of the high risk of well construction and low production efficiency,they are difficult to be recovered by using conventional oil production methods.As a result,this paper proposes an alternative design based on a combination of radial drilling,heat injection,and backfilling methods.Multi-branch holes are used to penetrate shallow gas hydrate reservoirs to expand the depressurization area,and heat injection is utilized as a supplement to improve gas production.Geotechnical information collected from an investigation site close to the offshore production well in the South China Sea is used to assess the essential components of this plan,including well construction stability and gas production behavior.It demonstrates that the hydraulic fracturing of the 60mbsf overburden layer can be prevented by regulating the drilling fluid densities.However,the traditional well structure is unstable,and the suction anchor is advised for better mechanical performance.The gas produc-tion rate can be significantly increased by combining hot water injection and depressurization methods.Additionally,the suitable produc-tion equipment already in use is discussed.
文摘Due to global warming, the general circulation, underlying surfaces characteristics, and geophysical and meteorological elements all show evident secular trends. This paper points out that when calculating the correlation of two variables containing their own obvious secular trends, the interannual correlation characteristics between the two variables may be distorted （overestimated or underestimated）. Numerical experiments in this paper show that if two variables have opposite secular trends, the correlation coefficient between the two variables is reduced （the positive correlation is underestimated, or the negative correlation is overestimated）; and if the two variables have the same sign of secular trends, the correlation coefficient between the two variables is increased （the positive correlation is overestimated, or the negative correlation is underestimated）. Numerical experiments also suggest that the effect of secular trends on the interannual correlation of the two variables is interchangeable, that is to say, as long as the values of the two trends are not changed, the two variables interchange their positions, and the effect of the secular trends on the interannual correlation coefficient of the two variables remains the same. If the two variables have the same-（opposite-） sign trends, the effect of secular trends on the interannal correlation coefficient is more （less） distinctive. A meteorological example is given.
文摘In this paper, the summer climate of 1991 in North China is simulated by using the high-resolution regional climate model (RegCM2) and the effects of the grassland desertification on summer drought in the central and the northern parts of North China as well as Mongolia are studied. It shows that the regional climate model essentially catches the characteristics on distribution and seasonal variation of the precipitation that keep good agreement with the observation. The desertification makes precipitation in the central part of North China during its flood period decrease obviously in July. The border of the precipitation or the soil moisture reduction in the desertification region extends about one latitude southeastward and beyond the southeast edge of the desertification. Thus, vegetation in the border region approaches desertification further. However, there appears evident difference of variation of precipitation over the whole desertification region. The grassland desertification greatly changes the transfers of fluxes between land and atmosphere. The secondary circulation or secondary circulation cells in the desertification region are excited and as a result moisture transport is changed. The variation of flux transfers between land and atmosphere as well as the vertical motion of atmosphere is closely related to that of precipitation.
基金the NKBRSF Project! G 1999043400 the CNSF Project! 49735180.
文摘Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version ie (BOZ) and the other B1Z based on B0Z and heterogeneously-treated by' combined approach' , were co 'pled to the meso-scale model MM4, respectively. Through the calculations of equations from the companion paper, parameters representing land surface heterogeneity and suitable for the coupling models were found out. Three cases were simulated for heavy rainfalls during 36 hours, and the sensitivity of short-term weather modeling to the land surface heterogeneity was tested. Through the analysis of the simulations of the three heavy rainfalls, it was demonstrated that BIZ, compared with BOZ, could more realistically reflect the features of the land surface heterogeneity, therefore could more realistically reproduce the circulation and precipitation amount in the heavy rainfall processes of the three cases. This shows that even short-term weather is sensitive to the land surface heterogeneity, which is more obvious with time passing, and whose influence is more pronounced in the lower layer and gradually extends to the middle and upper layer. Through the analysis of these simulations with BlZ, it is suggested that the bulk effect of smaller-scale fluxes (i.e., the momentum, water vapor and sensible heat fluxes) near the s ig nificantly-heterogeneous land surface is to change the larger-scale (i.e., meso-scale) circulation, and then to influence the development of the low-level jets and precipitation. And also, the complexity of the land-atmosphere interaction was shown in these simulations.
基金supported by the National Natural Science Foundation of China(Nos.51679079 and 51209080)the Fundamental Research Funds for the Central Universities(No.2014B17314)+3 种基金the Program for Excellent Innovative Talents of Hohai Universitythe Open Fund of State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University(HESS-1703)the Open Fund Program of Key Laboratory of Water & Sediment Science and Water Hazard Prevention,Changsha University of Science & Technology(2015SS03)the 111 Project(B12032)
文摘A finite difference model for solving Navier Stokes viscous liquid sloshing-wave interaction with baffles in a tank. equations with turbulence taken into accotmt is used to investigate The volume-of-fluid and virtual boundary force methods are employed to simulate free surface flow interaction with structures. A liquid sloshing experimental apparatus was established to evaluate the accuracy of the proposed model, as well as to study nonlinear sloshing in a prismatic tank with the baffles. Damping effects of sloshing in a rectangular tank with bottom-mounted vertical baffles and vertical baffles touching the free surface are studied numerically and experimentally. Good agreement is obtained between the present numerical results and experimental data. The numerical results match well with the current experimental data for strong nonlinear sloshing with large free surface slopes. The reduction in sloshing-wave elevation and impact pressure induced by the bottom-mounted vertical baffle and the vertical baffle touching the free surface is estimated by varying the external excitation frequency and the location and height of the vertical baffle under horizontal excitation.
文摘A method based on Giorgi (1997a, 1997b) and referred to as ’ combined approach’, which is a combi-nation of mosaic approach and analytical-statistical-dynamical approach, is proposed. Compared with those of other approaches, the main advantage of the combined approach is that it not only can represent both interpatch and intrapatch variability, but also cost less computational time when the land surface heterogeneity is considered. Because the independent variable of probability density function (PDF) is ex-tended to the single valued function of basic meteorological characteristic quantities, which is much more universal, the analytical expressions of the characteristic quantities (e.g., drag coefficient, snow coverage, leaf surface aerodynamical resistance) affected by roughness length are derived , when the roughness length(and / or the zero plane displacement) heterogeneity has been mainly taken into account with the approach. On the basis of the rule which the PDF parameters should follow, we choose a function y of the roughness length z 0 as the PDF independent variable, and set different values of the two parameters width ratio αn and height ratio γ of PDF (here a linear, symmetric PDF is applied) for sensitivity experiments, from which some conclusions can be drawn, e.g., relevant characteristic terms show different sensitivities to the heterogeneous characteristic (i.e., roughness length), which suggests that we should consider the heterogeneities of the more sensitive terms in our model instead of the heterogeneities of the rest, and which also implies that when the land surface scheme is coupled into the global or regional atmospheric model, sensitivity tests against the distribution of the heterogeneous characteristic are very necessary; when the parameter αn is close to zero, little heterogeneity is represented, and αn differs with cases, which have an upper limit of about 0.6; in the reasonable range of αn, a peak-like distribution of roughness length can be depicted by a small value of γ, etc.. Key words Representation of land surface heterogeneity - “ Combined approach” - Numerical experiment This work was supported by the National Sciences Foundation of China, Grant No.49875005 and the State Key Project (973) G19990434 (03).
基金China Special Fund for Meteorological Research in the Public Interest(GYHY201106008,GYHY201506003)China Meteorological Administration Special Fund for the Development of Numerical Weather Prediction(GRAPES)Research Innovation Program for College Graduates of Jiangsu Province(CXZZ13_0497)
文摘This paper further explores the estimating and expressing of dynamic balance constraints using statistical methods in GRAPES-3DVAR(Version GM). Unlike the single-level scheme which only considers the coupling between mass and wind at one level, the multi-level scheme considers the coupling between their vertical profiles and calculates the balanced mass field at each layer using the rotational wind at all model levels. A reformed ridge regression method is used in the new scheme to avoid the multicollinearity problem and reduce the noises caused by unbalanced mesoscale disturbances. The results of numerical experiments show that the new scheme can get more reasonable vertical mass field, reduce the magnitude of the adjustment by the initialization, and improve the potential temperature analysis performance. Furthermore, the results of forecast verification in January(winter) and July(summer) both confirm that the new scheme can significantly improve the temperature forecast accuracy and bring slight positive effects to the pressure and wind forecast.
基金National Science Foundation of China (No.50974059No.50934006)
文摘This paper puts forward a new rock fragmentation loading method of dual-cutter head combined dynamic and static loads. By applying the numerical simulation software - RFPA2D, we have done numerical experiment about the sihstone＇ s crushing effect by dynamic load on single cutter head without confining pressure, dynamic load on single cut- ter head with confining pressure 10 MPa and different dual-cutter heads spacing by combined dynamic and static loads with confining pressure 10 MPa. Experimental results show that the confining pressure can obviously affect the rock frag- mentation effect. Combined dynamic and static loads can greatly improve the rock fragmentation effect. There exists an optimal spacing of dual-cutter head that can make the rock fragmentation achieve the desired effect. Through analyzing the acoustic emission accumulative energy and quantity, the authors make a conclusion that the optimum spacing is 30 mm.
基金"973"Project(2009CB421500,2013CB430305)National Natural Science Foundation of China(40921160381,40705024,40875039)+1 种基金Special Scientific Research Fund of Meteorological Public Welfare of China(GYHY201006007,GYHY201006008,GYHY201006016)Shanghai Typhoon Research Foundation(2010ST09)
文摘Tropical cyclones(TCs) Lionrock,Kompasu,and Namtheun were formed successively within 40 hours in 2010.Over the next several days afterwards,these TCs exhibited unusual movements which made operational prediction difficult.Verifications are performed on the forecasts of the tracks of these TCs with six operational models,including three global and three regional models.Results showed that the trends of TC tracks could be reproduced by these models,whereas trajectory turning points and landfall locations were not simulated effectively.The special track of Lionrock should be associated with its direct interaction with Namtheun,according to a conceptual model of binary TC interaction.By contrast,the relation between Kompasu and Namtheun satisfied the criteria for a semi-direct interaction.Numerical experiments based on the Global and Regional Assimilation and Prediction System-Tropical Cyclone forecast Model(GRAPES-TCM) further confirmed the effect of Namtheun on the unusual tracks of Lionrock and Kompasu.Finally,the physical mechanism of binary TC interaction was preliminarily proposed.
基金Supported by National Scientific Foundation of China(Study on of Basis Theory and Prediction of Debris Flow,40025103)
文摘In order to improve and enhance the numerical modeling methods and its application on debris flow problems,a preliminary study has been proposed in accordance with the corrected water-sediment numerical model on the premise of revised resistance and sediment capacity equations.Firstly,an overview the recent re- search achievements on numerical simulation of debris flow has been conducted,the results shown that a gener- al numerical model for debris flow can not be existed at all because the complex rheol...
文摘A new remote sensing method is described to determine the vertical distribution and total content of atmospheric ozone. The method combines surface infrared, satellite infrared and ultraviolet channels. The width of the infrared channels is 0.01 cm-1, less than Lorentz half-width at the earth's surface, rather than the present width, because these channels can obtain information about variations in the ozone profile below the profile main-peak. The numerical experiments show that the method has a satisfactory precision in determining total ozone content, just about I percent error, and vertical distribution from the earth to 65 km space. In addition, some semi-analysis functions lor calculating backscattered ultraviolet and a relaxation equation are described in this paper.
基金Supported by the Collaborative Innovation Program of Hefei Science Center,CAS (Grant No.2019HSC-CIP015)the National Natural Science Foundation of China (Grant Nos.11875290,1170529,11875253,and 11975276)+2 种基金the Fundamental Research Funds for the Central Universities (Grant No.WK3420000004)the Anhui Provincial Natural Science Foundation (Grant No.2008085J04)the National Key Research and Development Program of China (Grant No.2019YFE03020004)。
文摘This research applies experimental measurements and NUBEAM,ONETWO and TRANSP modules to investigate the shine-through(ST)loss ratio and beam heating percentage of neutral beam injection on EAST.Measurements and simulations confirm that the ST loss ratio increases linearly with beam energy,and decreases exponentially with plasma density.Moreover,using the multi-step fitting method,we present analytical quantitative expressions of ST loss ratio and beam heating percentage,which are valuable for the high parameter long-pulse experiments of EAST.
基金supported by BMWi (Bundesministerium für Wirtschaft und Energie,Berlin)
文摘As is known, high-level radioactive waste （HLW） is commonly heat-emitting. Heat output from HLWwilldissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical（THMC） processes. In highly consolidated clayey rocks, thermal effects are particularly significantbecause of their very low permeability and water-saturated state. Thermal impact on the integrity of thegeological barriers is of most importance with regard to the long-term safety of repositories. This studyfocuses on numerical analysis of thermal effects on hydro-mechanical properties of clayey rock using acoupled thermo-mechanical multiphase flow （TH2M） model which is implemented in the finite elementprogramme OpenGeoSys （OGS）. The material properties of the numerical model are characterised by atransversal isotropic elastic model based on Hooke＇s law, a non-isothermal multiphase flow model basedon van Genuchten function and Darcy＇s law, and a transversal isotropic heat transport model based onFourier＇s law. In the numerical approaches, special attention has been paid to the thermal expansion ofthree different phases： gas, fluid and solid, which could induce changes in pore pressure and porosity.Furthermore, the strong swelling and shrinkage behaviours of clayey material are also considered in thepresent model. The model has been applied to simulate a laboratory heating experiment on claystone.The numerical model gives a satisfactory representation of the observed material behaviour in thelaboratory experiment. The comparison of the calculated results with the laboratory findings verifies thatthe simulation with the present numerical model could provide a deeper understanding of the observedeffects. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
基金financially supported by the State Oceanic Administration of China(Grant No.GHME2011CL01)the Program of State Key Laboratory of Coastal and Offshore Engineering(Grant No.LP1102)
文摘Vertical axis tidal current turbine is a promising device to extract energy from ocean current. One of the important components of the turbine is the connecting arm, which can bring about a significant effect on the pressure distribution along the span of the turbine blade, herein we call it 3D effect. However, so far the effect is rarely reported in the research, moreover, in numerical simulation. In the present study, a 3D numerical model of the turbine with the connecting arm was developed by using FLUENT software compiling the UDF（User Defined Function） command. The simulation results show that the pressure distribution along the span of blade with the connecting arm model is significantly different from those without the connecting arm. To facilitate the validation of numerical model, the laboratory experiment has been carried out by using three different types of NACA aerofoil connecting arm and circle section connecting arm. And results show that the turbine with NACA0012 connecting arm has the best start-up performance which is 0.346 m/s and the peak point of power conversion coefficient is around 0.33. A further study has been performed and a conclusion is drawn that the aerofoil and thickness of connecting arm are the most important factors on the power conversion coefficient of the vertical axis tidal current turbine.
基金Scientific Research Projects Specially for Public Welfare Industries(GYHY200906010)National Natural Science Foundation of China(41075034)Project 1009 for Wuhan Heavy Rain Institute
文摘In this paper, based on heavy rain numerical forecast model AREM(Advanced Regional Eta Model), two different initialization schemes, LAPS and GRAPES-3DVAR, are used to run assimilation experiments of AREM-LAPS and AREM-3DVAR with the same data source(NCEP forecast field, surface data and radio-soundings) during the period from 21 May to 30 July 2008 to investigate the effect of the two initialization schemes on the rainfall simulation. The result suggests that:(1) the forecast TS score by the AREM-LAPS is higher than that by the AREM-3DVAR for rainfall in different areas, at different valid time and with different intensity, especially for the heavy rain, rainstorm and extremely heavy rain;(2) the AREM-3DVAR can generally simulate the average rainfall distribution, but the forecast area is smaller and rainfall intensity is weaker than the observation, while the AREM-LAPS significantly improves the forecast;(3) the AREM-LAPS gives a better forecast for the south-north shift of rainfall bands and the rainfall intensity variation than the AREM-3DVAR;(4) the AREM-LAPS can give a better reproduction for the daily change in the mean-rainfall-rate of the main rain band, and rainfall intensity changes in the eastern part of Southwest China, the coastal area in South China, the middle-lower valleys of Yangtze river, the Valleys of Huaihe river, and Shandong peninsula, with the rainfall intensity roughly close to the observation, while the rainfall intensity simulated by the AREM-3DVAR is clearly weaker than the observation, especially in the eastern part of Southwest China; and(5) the comparison verification between the AREM-LAPS and AREM-3DVAR for more than 10 typical rainfall processes in the summer of 2008 indicates that the AREM-LAPS gives a much better forecast than AREM-3DVAR in rain-band area, rainfall location and intensity, and in particular, the rainfall intensity forecast is improved obviously.
基金National Program on Key Basic Research Project of China (973 Program) (2007CB411805 2010CB428505)National Natural Science Foundation of China (40830958)
文摘The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM.The monsoon indexes for East Asian summer monsoon and land-sea thermal difference,which characterize the intensity of the EASM,show an obvious increase during the onset period of the EASM.Moreover,the land-sea thermal difference is more sensitive to warmer SST.Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China,South China Sea,and the Western Pacific Ocean to the east of the Philippines.While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China,precipitation increases notably in northern China,the South China Sea,the East China Sea,the Yellow Sea,and the Western Pacific to the east of the Philippines.North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent.The surface air temperature shows a warming trend.The warming in the entire troposphere between 30oN and 50oN increases the land-sea thermal contrast,which plays an important role in the enhancement of the EASM.Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension.
文摘This paper proposed several new types of finite-difference methods for the shallow water equation in absolute coordinate system and put forward an effective two-step predictor-corrector method, a compact and iterative algorithm for five diagonal matrix. Then the iterative method was used for a multi-grid procedure for shallow water equation. A t last, an initial-boundary value problem was considered, and the numerical results show that the linear sinusoidal wave would successively evolve into conoidal wave.
文摘In this paper,the effect of water and air fluids on the behavior of a planing catamaran in calm water was studied separately in calm water by using experimental and numerical methods.Experiments were conducted in a towing tank over the Froude number range of 0.49–2.9 with two degrees of freedom.The model vessel displacement of 5.3 kg was implemented in experimental tests.Craft behavior was evaluated at the displacements of 5.3,4.6,and 4 kg by using the numerical method.The numerical simulation results for the hull’s resistance force were validated with similar experimental data.The fluid volume model was applied to simulate two-phase flow.The SST k-ωturbulence model was used to investigate the effect of turbulence on the catamaran.The results showed that in the planing mode,the contribution of air to pressure resistance increased by 55%,40%,and 60%at the mentioned displacements,whereas the contribution of air to friction resistance was less than 15%on average.The contribution of the air to the total lift force at the abovementioned displacements exceeded 70%,60%,and 50%in the planing mode but was less than 10%in the displacement mode.At the displacements of 5.3 and 4 kg,the area under the effect of maximum pressure moved around the center of gravity and caused porpoising longitudinal instability at the Froude numbers of 2.9 and 2.4,respectively.However,at the displacement of 4.6 kg,this effect did not occur,and the vessel maintained its stability.
文摘A numerical experiment on the formation and decay process of a mesolow on the plain east to the Taihang Mountains has been conducted. The dynamical effect of the special topography of the Taihang Mountains and the Yanshan Mountains on the formation of the mesolow is very important. Namely, the difference of the heating between the Taihang Mountains and the North China plain plays an important role in the formation and decay of the mesolow.
