The Power System Simulation Lab constructed specifically for the Three Gorges AC/DC hybrid transmissionstudy is equipped mainly with a real-time power system simulator, which can jointly operate with existing TNA andH...The Power System Simulation Lab constructed specifically for the Three Gorges AC/DC hybrid transmissionstudy is equipped mainly with a real-time power system simulator, which can jointly operate with existing TNA andHVDC Simulator respectively. Appraised by the State Power Corporation 3 years ago, this Lab was proved reachinginternational advanced level. Several large-scaled power system studies, such as the "Simplified Three Gorges PowerSystem Study" have achieved good results.[展开更多
A throttling experiment for the multi-hole orifice (MO) using water was conducted based on the conclusion of key parameters affecting the MO throttling performance. Testing MOs and standard orifice plates ( SO ) w...A throttling experiment for the multi-hole orifice (MO) using water was conducted based on the conclusion of key parameters affecting the MO throttling performance. Testing MOs and standard orifice plates ( SO ) were designed for the throttling experiment to compare the throttling effect using the equivalent diameter ratio (RED) and diameter ratio (RD ) as key parameters, respectively. Meanwhile, effective metrical conditions were provided for experimental accuracy. The throttling model form was determined according to the theoretical throttling model of SO. Then the unknown parameters involved were identified by experimental data. A good concordance between the modeling computation and experimental results shows a validation of the MO throtting model.展开更多
In absorption cycles,ionic liquid(IL)1,3-dimethylimidazolium tetrafluoroborate([Dmim]BF4)may be a promising absorbent of working pair using water as refrigerant.The vapor pressures of[Dmim]BF4 aqueous solution were me...In absorption cycles,ionic liquid(IL)1,3-dimethylimidazolium tetrafluoroborate([Dmim]BF4)may be a promising absorbent of working pair using water as refrigerant.The vapor pressures of[Dmim]BF4 aqueous solution were measured with the boiling-point method in the temperature range from 312.25 to 403.60 K and in the mass concentration range of 65%to 90%of[Dmim]BF4.The experimental data were correlated with an Antoine-type equation and the Non-Random Two-Liquid(NRTL)model,and the average absolute deviations between the experimental and calculated values were 1.06%and 1.15%,respectively.For the[Dmim]BF4 aqueous solution,the experimental vapor pressures show negative deviations from the calculated data with Raoult's law.For higher mass concentration of the IL,the deviation is more negative.In addition,the vapor pressures,the hydrophilicity and the solubility of[Dmim]BF4 aqueous solutions were compared with those of[Dmim]Cl aqueous solutions and [Bmim]BF4 aqueous solutions at IL-mole fraction of 0.20.展开更多
After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coeffici...After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coefficient and the water-pressure conductivity coefficient.The water transmissivity coefficient is approximated by a Taylorseries expansion of drawdown,and the water-pressure conductivity coefficient is obtained by the average drawdown.In this algorithm,the distance of the observation points from the pumping well must be short.When the distance is as short as the radius of the main pumping well,the data of the drawdown difference between the sidewall and the center of pumping well are difficult to measure,but the same results can be achieved based on the assumption that the drawdown difference approximates to the drawdown of the observation wells at a radial distance from the pumping well according to the algorithm.Without the help of charts,this algorithm is more concise and efficient,which has been verified by the test of water pumping project in Tianjin Binhai International Airport.展开更多
In this paper, towing tank experiments are conducted to study the behavior of flow on a model of the underwater vehicle with various shapes of bows, i.e. tango and standard bows in free surface motion tests. The total...In this paper, towing tank experiments are conducted to study the behavior of flow on a model of the underwater vehicle with various shapes of bows, i.e. tango and standard bows in free surface motion tests. The total resistances for different Froude numbers are considered experimentally. The towing tank is equipped with a trolley that can operate in through 0.05-6 m/s speed with ±0.02 m/s accuracy. Furthermore, the study is done on hydrodynamic coefficients i.e. total, residual and friction resistance coefficients, and the results are compared. Finally, the study on flow of wave fields around bows is done and wave filed around two bows are compared. The Froude number interval is between 0.099 and 0.349. Blockage fraction for the model is fixed to 0.005 3. The results showed that the residual resistance of the standard bow in 0.19 to 0.3 Froude number is more than the tango bow in surface motion which causes more total resistance for the submarine. Finally, details of wave generated by the bow are depicted and the effects of flow pattern on resistance drag are discussed.展开更多
Based on the measured data of geomagnetically induced currents (GIC) in Guangdong Ling' ao 500 kV power networks during several magnetic storms at the peak years of 23rd Solar Cycle, the GIC calculation results of ...Based on the measured data of geomagnetically induced currents (GIC) in Guangdong Ling' ao 500 kV power networks during several magnetic storms at the peak years of 23rd Solar Cycle, the GIC calculation results of 750 kV planning power grid in Shartxi, Gansu, Qinghai and Ningxia, the structure and characteristics of power networks from 500 kV to 1 000 kV, and super magnetic storm in 1859 are analyzed in this paper. Through the analysis, the possible impacts of extreme space weather on the future ultra-high voltage (UHV) grid, the security of large-scale power system in China are expounded, and the research suggestions coping with the strong solar storms are proposed.展开更多
Convection heat transfer coefficient and air pressure drop in sinter layer are important factors for the design of sinter cooling craft. Due to the lack of necessary data, the two parameters are studied by experimenta...Convection heat transfer coefficient and air pressure drop in sinter layer are important factors for the design of sinter cooling craft. Due to the lack of necessary data, the two parameters are studied by experimental method. The experimental results show that heat conduction of sinter impacts the measurement of convection heat transfer coefficient. Convection heat transfer increases with the increase of air volumetric flow rate. Sinter layer without small particles(sample I) gives higher convection heat transfer coefficient than that with small particles(sample II). Under the considered conditions, volumetric convection heat transfer coefficient is in the range of 400-1800 W/(m3·°C). Air pressure drop in sinter layer increases with the increase of normal superficial velocity, as well as with the rise of air temperature. Additionally, air pressure drop also depends on sinter particle size distribution. In considered experimental conditions, pressure drop in sinter sample II is 2-3 times that in sinter sample I, which resulted from 17% small scale particles in sinter sample II.展开更多
Boiling of water/triethyleneglycol(TEG)binary solution has a wide-ranging application in the gas processing engineering.Design,operation and optimization of the involved boilers require accurate prediction of boiling ...Boiling of water/triethyleneglycol(TEG)binary solution has a wide-ranging application in the gas processing engineering.Design,operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution.In this investigation,nucleate pool boiling heat transfer coefficient has been experimentally measured on a horizontal rod heater in water/TEG binary solutions in a wide range of concentrations and heat fluxes under ambient condition.The present experimental data are correlated using major existing correlations.In addition a correlation is presented for prediction of pool boiling heat transfer for the system in which the vapour pressure of one component is negligible.This model is based on the mass transfer rate equation for prediction of the concentration at the bubble vapor/liquid interface.Based on this prediction,the temperature of the interface and accordingly,the boiling heat transfer coefficient could be straightforwardly calculated from the known concentration at the interface.It is shown that this simple model has sufficient accuracy and is acceptable below the medium concentrations of TEG when the vapor equilibrium concentration of TEG is almost zero.The presented model excludes any tuning parameter and requires very few physical properties to apply.展开更多
Debris flows include a great diversity of grain sizes with inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidit...Debris flows include a great diversity of grain sizes with inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidity of debris flows, although the behavior and influence of fine sediment in debris flows have not been examined sufficiently. This study used flume tests to detect the effect of fine sediment on the fluidity of laboratory debris flows consisting of particles with various diameters. From the experiments, the greatest sediment concentration and flow depth were observed in the debris flows mixed with fine sediment indicating increased flow resistance. The experimental friction coefficient was then compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow. The theoretical friction coefficient was obtained from two models with different fine-sediment treatments: assuming that all of the fine sediments were solid particles or that the particles consisted of a fluid phase involving pore water liquefaction. From the comparison of the friction coefficients, a fully liquefaction state was detected for the fine particle mixture. When the mixing ratio and particle size of the fine sediment were different, some other eases were considered to be in a partially liquefied transition state. These results imply that the liquefaction of fine sediment in debris flows was induced not only by the geometric conditions such as particle sizes, but also by the flow conditions.展开更多
Submersible buoy systems are widely used for oceanographic research,ocean engineering and coastal defense.Severe sea environment has obvious effects on the dynamics of submersible buoy systems.Huge tension can occur a...Submersible buoy systems are widely used for oceanographic research,ocean engineering and coastal defense.Severe sea environment has obvious effects on the dynamics of submersible buoy systems.Huge tension can occur and may cause the snap of cables,especially during the deployment period.This paper studies the deployment dynamics of submersible buoy systems with numerical and experimental methods.By applying the lumped mass approach,a three-dimensional multi-body model of submersible buoy system is developed considering the hydrodynamic force,tension force and impact force between components of submersible buoy system and seabed.Numerical integration method is used to solve the differential equations.The simulation output includes tension force,trajectory,profile and dropping location and impact force of submersible buoys.In addition,the deployment experiment of a simplified submersible buoy model was carried out.The profile and different nodes' velocities of the submersible buoy are obtained.By comparing the results of the two methods,it is found that the numerical model well simulates the actual process and conditions of the experiment.The simulation results agree well with the results of the experiment such as gravity anchor's location and velocities of different nodes of the submersible buoy.The study results will help to understand the conditions of submersible buoy's deployment,operation and recovery,and can be used to guide the design and optimization of the system.展开更多
There is low formation pressure coefficient and high formation temperature in ludong-wucaiwan area. Gas cut and gas channeling happen seriously during oil and gas well cementing. The existing anti-migration additive h...There is low formation pressure coefficient and high formation temperature in ludong-wucaiwan area. Gas cut and gas channeling happen seriously during oil and gas well cementing. The existing anti-migration additive has only effects on single trait, so it is difficult to meet cementing requirement. According to this situation we could use latex slurry to anti-gas channeling. We have synthesised a set of anti-gas channeling lightweight temperature-resistant latex slurry and formed a new channeling preventing latex slurry through plenty of previous laboratory experiments. Finally the performance of latex slurry on temperature-resistant, anti-gas channeling and the anti-gas channeling of cement paste are studied. The experimental results show that this latex system has strong temperature-resistant and anti-gas channeling, which completely meet the requirement of cementing in this area.展开更多
In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients (APGs) is conducted by using Reynolds-averaged Navier-Stokes (RANS) equations. This research chooses si...In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients (APGs) is conducted by using Reynolds-averaged Navier-Stokes (RANS) equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox (2006) k-co are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.展开更多
The problem of mathematical simulation of motion of dynamic systems characteristics and their coincidence with real experimental data which correspond to these characteristics is investigated in this paper. Mathematic...The problem of mathematical simulation of motion of dynamic systems characteristics and their coincidence with real experimental data which correspond to these characteristics is investigated in this paper. Mathematical description of process will be named as adequate mathematical description if the results of mathematical simulation by the help of this description coincide with experiment with inaccuracy of initial data. The synthesis of such description is very important at mathematical modeling and forecast of motion of real physical phenomena. The specified problem is still poorly investigated and hardly adapted to formalization. The requirements to the adequate mathematical description of dynamic system are considered for the case when mathematical description of dynamic systems is represented by linear system of the ordinary differential equations. In this paper the mathematical model of process is given a priori with inexact parameters and then the models of external loads are being determined for which the results of simulation coincide with experiment. The methods of obtaining of the steady models of external loads are suggested. The example of the adequate description construction of the main mechanical line dynamics of rolling mill is given.展开更多
In a golf course located at El Kantaoui, Sousse, Tunisia, this study was carried out over a sandy soil grassy sward to investigate the effects of mechanical aeration (perforation of the sward with an aerators machine...In a golf course located at El Kantaoui, Sousse, Tunisia, this study was carried out over a sandy soil grassy sward to investigate the effects of mechanical aeration (perforation of the sward with an aerators machine called "Vertidrain") on its compaction and hydraulic conductivity. For this purpose, many soil cores were extracted using a 1.6 e.g. m effective width Verti-Drain aerator equipped with hollow spades spaced 65 e.g. mm apart. Aeration was performed at a rate of 350 holes/m2. Soil resistance to penetration and permeability were determined at the initial state before aeration as well as 10, 20, and 30 days after aeration. Compared to the initial state, the results showed that mechanical aeration greatly affects the grassy sward ground by reducing its resistance to penetration as 35% and 43% decrease in penetration resistance were noticed at 5 e.g. cm depth 10 and 20 days after aeration, respectively. Also, resistance to penetration decreased by 41% and 48% at 15 e.g. cm depth during the same two periods of time with a relatively constant moisture content. However, soil resistance to penetration at 5 and 15 e.g. cm depths only decreased by 21% and 26%, respectively. Regarding the soil hydraulic conductivity measured after aeration, a significant improvement at the 1% level with the method of variance analysis, was observed compared to that at the initial state (4.9 e.g. cm hl). Indeed, the hydraulic conductivity was 12.5, 13, and 14.1 e.g. cm h-1 10, 20, and 30 days after aeration, respectively.展开更多
As an experimental technique, it’s desired that the temperature in specimen is uniform in high temperature split Hopkinson pressure bar (SHPB) experiments. However, the temperature in specimen decreases and the tempe...As an experimental technique, it’s desired that the temperature in specimen is uniform in high temperature split Hopkinson pressure bar (SHPB) experiments. However, the temperature in specimen decreases and the temperature of bars increases when specimen starts to contact with bars, which induces the nonuniform temperature distribution in specimen, and may result in inac-curacy of experimental results. In this paper, the temperature distributions of specimen and bars in high temperature SHPB experiments were investigated while the specimen was heated alone. Firstly, the temperature history of specimen was measured at different initial temperatures by ex-periments, then simulation was carried out. Simulation results were consistent with experimental results by adjusting the thermal contact coefficient between specimen and bars. By this way, the thermal contact coefficient and simulation results were validated, and the proper cold contact times of specimen and bars in high temperature SHPB experiments were discussed. Finally, the results were compared with those in references.展开更多
Based on real-time digital simulations(RTDS),a laboratory environment similar to the real-time operation situation of the Three Gorges Hydropower Station is established.Then,the causes for the power fluctuation of the...Based on real-time digital simulations(RTDS),a laboratory environment similar to the real-time operation situation of the Three Gorges Hydropower Station is established.Then,the causes for the power fluctuation of the second generator by errors in the rotor rotating speed calculation are found,and the tuning method of the speed related parameters are given.The damping and reverse tuning characteristics of power system stabilizers(PSSs)in the digital automatic voltage regulator(AVR)are compared and investigated in the frequency range of 0.18-1.1 Hz.The efficiency of the proposed tuning method for ensuring power system stability is verified by RTDS.Finally,field tests show the validity of the laboratory test results.展开更多
As the voltage has local characteristics in a power system, system voltage control has depended on human experts in distribution substation local reactive power control station so far in Korea. Since coordinative auto...As the voltage has local characteristics in a power system, system voltage control has depended on human experts in distribution substation local reactive power control station so far in Korea. Since coordinative automatic control has been possible due to the recent advances in computers and communication networks, the hierarchical voltage control system, consisting of primary, secondary, and tertiary control, has been applied in several European countries. Recently the Korea power system has been operated more closely to stability limits because of rapid growth in load-demand as seen in Europe. For this reasons, Korea electric power corporation recognized the need of the voltage control system and developed the voltage control system. This paper presents an intelligent voltage control system for domestic power system using numerical algorithm based on the sensitivity matrix and the expert system. Dynamic characteristics of the developed system are investigated using EMTDC (electromagnetic transient DC analysis program) and RTDS (real time digital simulator). Several case studies showed the promising performance.展开更多
Within the OECD/NEA Benchmarking of Thermal-Hydraulic Loop Models for Lead-Alloy Cooled Advanced Nuclear Energy Systems (LACANES), the Institute for Neutron Physics and Reactor Technology takes part in the validatio...Within the OECD/NEA Benchmarking of Thermal-Hydraulic Loop Models for Lead-Alloy Cooled Advanced Nuclear Energy Systems (LACANES), the Institute for Neutron Physics and Reactor Technology takes part in the validation process of system codes and the characterization of the thermal-hydraulic behavior of an experimental loop operated with liquid lead-bismuth-eutectics. To confirm the calculations, the results were compared to experimental data obtained from the HELIOS facility at the Seoul National University and to the results of other benchmark participants. The comparison showed that the calculations are within measurement tolerance but nevertheless discrepancies among the participants exist. The pressure drop estimation is determined by a variety of empirical correlations for the friction and the form loss coefficients. Hence, uncertainty and sensitivity measures were applied to find out which parameter is more relevant for the overall pressure drop. In the frame of this investigation, the system code TRACE and the software system for uncertainty and sensitivity, SUSA, were used. The results show that the total pressure drop varies between -30 and +15% related to the reference case.展开更多
文摘The Power System Simulation Lab constructed specifically for the Three Gorges AC/DC hybrid transmissionstudy is equipped mainly with a real-time power system simulator, which can jointly operate with existing TNA andHVDC Simulator respectively. Appraised by the State Power Corporation 3 years ago, this Lab was proved reachinginternational advanced level. Several large-scaled power system studies, such as the "Simplified Three Gorges PowerSystem Study" have achieved good results.[
基金the National Natural Science Foundation of China(Grant No.50578049)
文摘A throttling experiment for the multi-hole orifice (MO) using water was conducted based on the conclusion of key parameters affecting the MO throttling performance. Testing MOs and standard orifice plates ( SO ) were designed for the throttling experiment to compare the throttling effect using the equivalent diameter ratio (RED) and diameter ratio (RD ) as key parameters, respectively. Meanwhile, effective metrical conditions were provided for experimental accuracy. The throttling model form was determined according to the theoretical throttling model of SO. Then the unknown parameters involved were identified by experimental data. A good concordance between the modeling computation and experimental results shows a validation of the MO throtting model.
基金Supported by the National Natural Science Foundation of China(50890184)the National Basic Research Program of China(2010CB227304)
文摘In absorption cycles,ionic liquid(IL)1,3-dimethylimidazolium tetrafluoroborate([Dmim]BF4)may be a promising absorbent of working pair using water as refrigerant.The vapor pressures of[Dmim]BF4 aqueous solution were measured with the boiling-point method in the temperature range from 312.25 to 403.60 K and in the mass concentration range of 65%to 90%of[Dmim]BF4.The experimental data were correlated with an Antoine-type equation and the Non-Random Two-Liquid(NRTL)model,and the average absolute deviations between the experimental and calculated values were 1.06%and 1.15%,respectively.For the[Dmim]BF4 aqueous solution,the experimental vapor pressures show negative deviations from the calculated data with Raoult's law.For higher mass concentration of the IL,the deviation is more negative.In addition,the vapor pressures,the hydrophilicity and the solubility of[Dmim]BF4 aqueous solutions were compared with those of[Dmim]Cl aqueous solutions and [Bmim]BF4 aqueous solutions at IL-mole fraction of 0.20.
基金Supported by Major State Basic Research Development Program of China("973" Program,No.2010CB732106)
文摘After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coefficient and the water-pressure conductivity coefficient.The water transmissivity coefficient is approximated by a Taylorseries expansion of drawdown,and the water-pressure conductivity coefficient is obtained by the average drawdown.In this algorithm,the distance of the observation points from the pumping well must be short.When the distance is as short as the radius of the main pumping well,the data of the drawdown difference between the sidewall and the center of pumping well are difficult to measure,but the same results can be achieved based on the assumption that the drawdown difference approximates to the drawdown of the observation wells at a radial distance from the pumping well according to the algorithm.Without the help of charts,this algorithm is more concise and efficient,which has been verified by the test of water pumping project in Tianjin Binhai International Airport.
文摘In this paper, towing tank experiments are conducted to study the behavior of flow on a model of the underwater vehicle with various shapes of bows, i.e. tango and standard bows in free surface motion tests. The total resistances for different Froude numbers are considered experimentally. The towing tank is equipped with a trolley that can operate in through 0.05-6 m/s speed with ±0.02 m/s accuracy. Furthermore, the study is done on hydrodynamic coefficients i.e. total, residual and friction resistance coefficients, and the results are compared. Finally, the study on flow of wave fields around bows is done and wave filed around two bows are compared. The Froude number interval is between 0.099 and 0.349. Blockage fraction for the model is fixed to 0.005 3. The results showed that the residual resistance of the standard bow in 0.19 to 0.3 Froude number is more than the tango bow in surface motion which causes more total resistance for the submarine. Finally, details of wave generated by the bow are depicted and the effects of flow pattern on resistance drag are discussed.
基金National Nature Science Foundation of China (No.50477039 No.50677020)National High Technology Research and Development Program of China("863"Program) (No.2007AA04Z425)
文摘Based on the measured data of geomagnetically induced currents (GIC) in Guangdong Ling' ao 500 kV power networks during several magnetic storms at the peak years of 23rd Solar Cycle, the GIC calculation results of 750 kV planning power grid in Shartxi, Gansu, Qinghai and Ningxia, the structure and characteristics of power networks from 500 kV to 1 000 kV, and super magnetic storm in 1859 are analyzed in this paper. Through the analysis, the possible impacts of extreme space weather on the future ultra-high voltage (UHV) grid, the security of large-scale power system in China are expounded, and the research suggestions coping with the strong solar storms are proposed.
基金Project(51306198)supported by the National Natural Science Foundation of China
文摘Convection heat transfer coefficient and air pressure drop in sinter layer are important factors for the design of sinter cooling craft. Due to the lack of necessary data, the two parameters are studied by experimental method. The experimental results show that heat conduction of sinter impacts the measurement of convection heat transfer coefficient. Convection heat transfer increases with the increase of air volumetric flow rate. Sinter layer without small particles(sample I) gives higher convection heat transfer coefficient than that with small particles(sample II). Under the considered conditions, volumetric convection heat transfer coefficient is in the range of 400-1800 W/(m3·°C). Air pressure drop in sinter layer increases with the increase of normal superficial velocity, as well as with the rise of air temperature. Additionally, air pressure drop also depends on sinter particle size distribution. In considered experimental conditions, pressure drop in sinter sample II is 2-3 times that in sinter sample I, which resulted from 17% small scale particles in sinter sample II.
文摘Boiling of water/triethyleneglycol(TEG)binary solution has a wide-ranging application in the gas processing engineering.Design,operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution.In this investigation,nucleate pool boiling heat transfer coefficient has been experimentally measured on a horizontal rod heater in water/TEG binary solutions in a wide range of concentrations and heat fluxes under ambient condition.The present experimental data are correlated using major existing correlations.In addition a correlation is presented for prediction of pool boiling heat transfer for the system in which the vapour pressure of one component is negligible.This model is based on the mass transfer rate equation for prediction of the concentration at the bubble vapor/liquid interface.Based on this prediction,the temperature of the interface and accordingly,the boiling heat transfer coefficient could be straightforwardly calculated from the known concentration at the interface.It is shown that this simple model has sufficient accuracy and is acceptable below the medium concentrations of TEG when the vapor equilibrium concentration of TEG is almost zero.The presented model excludes any tuning parameter and requires very few physical properties to apply.
基金supported by Grant-in-Aid for Scientific Research (Grant No.22780140,2010),from the Ministry of Education,Science,Sports,and Culture,of Japan
文摘Debris flows include a great diversity of grain sizes with inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidity of debris flows, although the behavior and influence of fine sediment in debris flows have not been examined sufficiently. This study used flume tests to detect the effect of fine sediment on the fluidity of laboratory debris flows consisting of particles with various diameters. From the experiments, the greatest sediment concentration and flow depth were observed in the debris flows mixed with fine sediment indicating increased flow resistance. The experimental friction coefficient was then compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow. The theoretical friction coefficient was obtained from two models with different fine-sediment treatments: assuming that all of the fine sediments were solid particles or that the particles consisted of a fluid phase involving pore water liquefaction. From the comparison of the friction coefficients, a fully liquefaction state was detected for the fine particle mixture. When the mixing ratio and particle size of the fine sediment were different, some other eases were considered to be in a partially liquefied transition state. These results imply that the liquefaction of fine sediment in debris flows was induced not only by the geometric conditions such as particle sizes, but also by the flow conditions.
基金supported by the Program for Excellent University Talents in New Century (NCET-12-0500)the National Natural Science Foundation of China (No.51175484)+2 种基金the Science Foundation of Shandong Province (No.ZR2010EM052)the support of the Project 111 (No.B14028)the Key Ocean Engineering Laboratory of Shandong Province
文摘Submersible buoy systems are widely used for oceanographic research,ocean engineering and coastal defense.Severe sea environment has obvious effects on the dynamics of submersible buoy systems.Huge tension can occur and may cause the snap of cables,especially during the deployment period.This paper studies the deployment dynamics of submersible buoy systems with numerical and experimental methods.By applying the lumped mass approach,a three-dimensional multi-body model of submersible buoy system is developed considering the hydrodynamic force,tension force and impact force between components of submersible buoy system and seabed.Numerical integration method is used to solve the differential equations.The simulation output includes tension force,trajectory,profile and dropping location and impact force of submersible buoys.In addition,the deployment experiment of a simplified submersible buoy model was carried out.The profile and different nodes' velocities of the submersible buoy are obtained.By comparing the results of the two methods,it is found that the numerical model well simulates the actual process and conditions of the experiment.The simulation results agree well with the results of the experiment such as gravity anchor's location and velocities of different nodes of the submersible buoy.The study results will help to understand the conditions of submersible buoy's deployment,operation and recovery,and can be used to guide the design and optimization of the system.
文摘There is low formation pressure coefficient and high formation temperature in ludong-wucaiwan area. Gas cut and gas channeling happen seriously during oil and gas well cementing. The existing anti-migration additive has only effects on single trait, so it is difficult to meet cementing requirement. According to this situation we could use latex slurry to anti-gas channeling. We have synthesised a set of anti-gas channeling lightweight temperature-resistant latex slurry and formed a new channeling preventing latex slurry through plenty of previous laboratory experiments. Finally the performance of latex slurry on temperature-resistant, anti-gas channeling and the anti-gas channeling of cement paste are studied. The experimental results show that this latex system has strong temperature-resistant and anti-gas channeling, which completely meet the requirement of cementing in this area.
基金Foundation item: Supported by the National Natural Science Foundation of China (Nos.51309040, 51379033, 51209027, 51309025), Open Research Fund of State Key Laboratory of Ocean Engineering (Shanghai Jiao Tong University) (Grant No.1402), and Fundamental Research Fund for the Central Universities (DMU3132015089).
文摘In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients (APGs) is conducted by using Reynolds-averaged Navier-Stokes (RANS) equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox (2006) k-co are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.
文摘The problem of mathematical simulation of motion of dynamic systems characteristics and their coincidence with real experimental data which correspond to these characteristics is investigated in this paper. Mathematical description of process will be named as adequate mathematical description if the results of mathematical simulation by the help of this description coincide with experiment with inaccuracy of initial data. The synthesis of such description is very important at mathematical modeling and forecast of motion of real physical phenomena. The specified problem is still poorly investigated and hardly adapted to formalization. The requirements to the adequate mathematical description of dynamic system are considered for the case when mathematical description of dynamic systems is represented by linear system of the ordinary differential equations. In this paper the mathematical model of process is given a priori with inexact parameters and then the models of external loads are being determined for which the results of simulation coincide with experiment. The methods of obtaining of the steady models of external loads are suggested. The example of the adequate description construction of the main mechanical line dynamics of rolling mill is given.
文摘In a golf course located at El Kantaoui, Sousse, Tunisia, this study was carried out over a sandy soil grassy sward to investigate the effects of mechanical aeration (perforation of the sward with an aerators machine called "Vertidrain") on its compaction and hydraulic conductivity. For this purpose, many soil cores were extracted using a 1.6 e.g. m effective width Verti-Drain aerator equipped with hollow spades spaced 65 e.g. mm apart. Aeration was performed at a rate of 350 holes/m2. Soil resistance to penetration and permeability were determined at the initial state before aeration as well as 10, 20, and 30 days after aeration. Compared to the initial state, the results showed that mechanical aeration greatly affects the grassy sward ground by reducing its resistance to penetration as 35% and 43% decrease in penetration resistance were noticed at 5 e.g. cm depth 10 and 20 days after aeration, respectively. Also, resistance to penetration decreased by 41% and 48% at 15 e.g. cm depth during the same two periods of time with a relatively constant moisture content. However, soil resistance to penetration at 5 and 15 e.g. cm depths only decreased by 21% and 26%, respectively. Regarding the soil hydraulic conductivity measured after aeration, a significant improvement at the 1% level with the method of variance analysis, was observed compared to that at the initial state (4.9 e.g. cm hl). Indeed, the hydraulic conductivity was 12.5, 13, and 14.1 e.g. cm h-1 10, 20, and 30 days after aeration, respectively.
文摘As an experimental technique, it’s desired that the temperature in specimen is uniform in high temperature split Hopkinson pressure bar (SHPB) experiments. However, the temperature in specimen decreases and the temperature of bars increases when specimen starts to contact with bars, which induces the nonuniform temperature distribution in specimen, and may result in inac-curacy of experimental results. In this paper, the temperature distributions of specimen and bars in high temperature SHPB experiments were investigated while the specimen was heated alone. Firstly, the temperature history of specimen was measured at different initial temperatures by ex-periments, then simulation was carried out. Simulation results were consistent with experimental results by adjusting the thermal contact coefficient between specimen and bars. By this way, the thermal contact coefficient and simulation results were validated, and the proper cold contact times of specimen and bars in high temperature SHPB experiments were discussed. Finally, the results were compared with those in references.
文摘Based on real-time digital simulations(RTDS),a laboratory environment similar to the real-time operation situation of the Three Gorges Hydropower Station is established.Then,the causes for the power fluctuation of the second generator by errors in the rotor rotating speed calculation are found,and the tuning method of the speed related parameters are given.The damping and reverse tuning characteristics of power system stabilizers(PSSs)in the digital automatic voltage regulator(AVR)are compared and investigated in the frequency range of 0.18-1.1 Hz.The efficiency of the proposed tuning method for ensuring power system stability is verified by RTDS.Finally,field tests show the validity of the laboratory test results.
文摘As the voltage has local characteristics in a power system, system voltage control has depended on human experts in distribution substation local reactive power control station so far in Korea. Since coordinative automatic control has been possible due to the recent advances in computers and communication networks, the hierarchical voltage control system, consisting of primary, secondary, and tertiary control, has been applied in several European countries. Recently the Korea power system has been operated more closely to stability limits because of rapid growth in load-demand as seen in Europe. For this reasons, Korea electric power corporation recognized the need of the voltage control system and developed the voltage control system. This paper presents an intelligent voltage control system for domestic power system using numerical algorithm based on the sensitivity matrix and the expert system. Dynamic characteristics of the developed system are investigated using EMTDC (electromagnetic transient DC analysis program) and RTDS (real time digital simulator). Several case studies showed the promising performance.
文摘Within the OECD/NEA Benchmarking of Thermal-Hydraulic Loop Models for Lead-Alloy Cooled Advanced Nuclear Energy Systems (LACANES), the Institute for Neutron Physics and Reactor Technology takes part in the validation process of system codes and the characterization of the thermal-hydraulic behavior of an experimental loop operated with liquid lead-bismuth-eutectics. To confirm the calculations, the results were compared to experimental data obtained from the HELIOS facility at the Seoul National University and to the results of other benchmark participants. The comparison showed that the calculations are within measurement tolerance but nevertheless discrepancies among the participants exist. The pressure drop estimation is determined by a variety of empirical correlations for the friction and the form loss coefficients. Hence, uncertainty and sensitivity measures were applied to find out which parameter is more relevant for the overall pressure drop. In the frame of this investigation, the system code TRACE and the software system for uncertainty and sensitivity, SUSA, were used. The results show that the total pressure drop varies between -30 and +15% related to the reference case.