The data information transfer and time marching strategies between computational fluid dynamics （CFD） and computational structural dynamics （CSD） play crucial roles on the aeroelastic analysis in a time domain. An...The data information transfer and time marching strategies between computational fluid dynamics （CFD） and computational structural dynamics （CSD） play crucial roles on the aeroelastic analysis in a time domain. An improved CFD/CSD coupled system is designed, including an interpolation method and an improved loosely coupled algorithm. The interpolation method based on boundary element method （BEM） is developed to transfer aerodynamic loads and structural displacements between CFD and CSD grid systems, it can be universally used in fluid structural interaction solution by keeping energy conservation. The improved loosely coupled algo-rithm is designed, thus it improves the computational accuracy and efficiency. The new interface is performed on the two-dimensional （2-D） extrapolation and the aeroelastie response of AGARD445.6 wing. Results show that the improved interface has a superior accuracy.展开更多
The improved current-doubler-rectifier zero-voltage-switching PWM full-bridge converter (CDR ZVS PWM FB converter) achieves ZVS for the switches in a wide load range with the use of the energy stored in the output fil...The improved current-doubler-rectifier zero-voltage-switching PWM full-bridge converter (CDR ZVS PWM FB converter) achieves ZVS for the switches in a wide load range with the use of the energy stored in the output filter inductances, and the rectifier diodes commute naturally, therefore no oscillation and voltage spike occurs. The transformer needs no special manufacture method to limit the leakage inductance. The ZVS achievement and the design considerations for the output filter inductances and the blocking capacitor are discussed for the improved CDR ZVS PWM FB converter. A 540 W prototype converter is built in the lab to verify the operational principle and design considerations for the improved converter, the experimental results are also included.展开更多
The use of design method considering a coil temperature to maximize the thrust density of a double side coreless permanent magnet linear synchronous motor(PMLSM) was presented.The optimal current density where the coi...The use of design method considering a coil temperature to maximize the thrust density of a double side coreless permanent magnet linear synchronous motor(PMLSM) was presented.The optimal current density where the coil temperature reaches an allowable temperature with heat analysis was applied to a magnetic circuit design.Changing optimal current density is verified whenever the design parameters of the motor are altered.The design parameters of the motor were applied to thrust calculation.In this way,the optimal model,which is a reversal of the existing design method,is deduced.The results were compared with the experimental data to verify their validity.When the convection heat transfer coefficient is applied to other models,the results of the analysis and test values show good concordance.The method proposed has some limitations.展开更多
Semiconductor nanowires （NW） possess several beneficial properties for efficient conversion of solar energy into electricity and chemical energy. Due to their efficient absorption of light, short distances for minor...Semiconductor nanowires （NW） possess several beneficial properties for efficient conversion of solar energy into electricity and chemical energy. Due to their efficient absorption of light, short distances for minority carriers to travel, high surface-to-volume ratios, and the availability of scalable synthesis methods, they provide a pathway to address the low cost-to-power requirements for widescale adaptation of solar energy conversion technologies. Here we highlight recent progress in our group towards implementation of NW components as photovoltaic and photoelectrochemical energy conversion devices. An emphasis is placed on the unique properties of these one-dimensional （1D） structures, which enable the use of abundant, low-cost materials and improved energy conversion efficiency compared to bulk devices.展开更多
The constructal optimizations of T-shaped fin with two-dimensional heat transfer model are carried out by finite element method and taking the minimization of equivalent thermal resistance based on entransy dissipatio...The constructal optimizations of T-shaped fin with two-dimensional heat transfer model are carried out by finite element method and taking the minimization of equivalent thermal resistance based on entransy dissipation and the minimization of maximum thermal resistance as optimization objectives, respectively. The effects of the global parameter a (integrating the coefficient of convective heat transfer, the overall area occupied by fin and its thermal conductivity) and the volume fraction ? of fin on the minimums of equivalent thermal resistance and maximum thermal resistance as well as their corresponding optimal configurations are analyzed. The comparison of the results based on the above two optimization objectives is conducted. The results show that the optimal structures based on the two optimization objectives are obviously different from each other. Compared with the optimization result by taking the minimization of maximum thermal resistance as the objective, the optimization result by taking the equivalent thermal resistance minimization as the objective can reduce the average temperature difference in the fin obviously. The increases of a and ? can all improve the working status of local hot spot and the global heat transfer performance of the system. But the improvement effects of the increases of a and ? on the minimization of equivalent thermal resistance are different from those on the minimization of maximum thermal resistance. For either objective, the effect of a is different from that of ?. The T-shaped fin with minimum equivalent thermal resistance is much taller than that with minimum maximum thermal resistance; for either optimization objective, the stem of fin is thicker than the branches of fin, and the stem thickness is relatively close to branch thickness when the minimization of equivalent thermal resistance is taken as the optimization objective. The T-shaped fin with flat stem and slender branches can benefit the reduction of the maximum thermal resistance.展开更多
After Bénard＇s experiment in 1900, Rayleigh formulated heat convection problems by the Oberbeck-Boussinesq approximation in the horizontal strip domain in 1916. The pattern formations have been investigated by t...After Bénard＇s experiment in 1900, Rayleigh formulated heat convection problems by the Oberbeck-Boussinesq approximation in the horizontal strip domain in 1916. The pattern formations have been investigated by the bifurcation theory, weakly nonlinear theories and computational approaches. The boundary conditions for the velocity on the upper and lower boundaries are usually assumed as stress-free or no-slip. In the first part of this paper, some bifurcation pictures for the case of the stress-free on the upper boundary and the no-slip on the lower boundary are obtained. In the second part of this paper, the bifurcation pictures for the case of the stress-free on both boundaries by a computer assisted proof are verified. At last., Bénard-Marangoni heat convections for the ease of the free surface of the upper boundary are considered.展开更多
The natural convective heat transfer performance and thermo-fluidic characteristics of honeycombs with/without chimney extensions are numerically investigated.The present numerical simulations are validated by the pur...The natural convective heat transfer performance and thermo-fluidic characteristics of honeycombs with/without chimney extensions are numerically investigated.The present numerical simulations are validated by the purposely-designed experimental measurements on honeycombs with/without chimney.Good agreement between numerical simulation and experimental measurement is obtained.The influences of inclination angle and geometric parameters such as cell shape,streamwise and spanwise length are also numerically quantified.With the increment in inclination angle,the overall heat transfer rate decreases for the honeycombs with/without chimney.For honeycombs with the same void volume fraction but different cell shapes,there is little difference on the overall heat transfer rate.To enhance the natural convective heat transfer of honeycombs,these techniques including increasing the length of honeycomb in the streamwise/spanwise direction,increasing the thermal conductivity of hon-eycomb structure or adding a chimney extension may be helpful.展开更多
基金Supported by the Ph.D.Program Foundation of Ministry of Education of China (20070699054)~~
文摘The data information transfer and time marching strategies between computational fluid dynamics （CFD） and computational structural dynamics （CSD） play crucial roles on the aeroelastic analysis in a time domain. An improved CFD/CSD coupled system is designed, including an interpolation method and an improved loosely coupled algorithm. The interpolation method based on boundary element method （BEM） is developed to transfer aerodynamic loads and structural displacements between CFD and CSD grid systems, it can be universally used in fluid structural interaction solution by keeping energy conservation. The improved loosely coupled algo-rithm is designed, thus it improves the computational accuracy and efficiency. The new interface is performed on the two-dimensional （2-D） extrapolation and the aeroelastie response of AGARD445.6 wing. Results show that the improved interface has a superior accuracy.
文摘The improved current-doubler-rectifier zero-voltage-switching PWM full-bridge converter (CDR ZVS PWM FB converter) achieves ZVS for the switches in a wide load range with the use of the energy stored in the output filter inductances, and the rectifier diodes commute naturally, therefore no oscillation and voltage spike occurs. The transformer needs no special manufacture method to limit the leakage inductance. The ZVS achievement and the design considerations for the output filter inductances and the blocking capacitor are discussed for the improved CDR ZVS PWM FB converter. A 540 W prototype converter is built in the lab to verify the operational principle and design considerations for the improved converter, the experimental results are also included.
基金Work supported by the Second Stage of Brain Korea 21 ProjectsChangwon National University in 2009-2010
文摘The use of design method considering a coil temperature to maximize the thrust density of a double side coreless permanent magnet linear synchronous motor(PMLSM) was presented.The optimal current density where the coil temperature reaches an allowable temperature with heat analysis was applied to a magnetic circuit design.Changing optimal current density is verified whenever the design parameters of the motor are altered.The design parameters of the motor were applied to thrust calculation.In this way,the optimal model,which is a reversal of the existing design method,is deduced.The results were compared with the experimental data to verify their validity.When the convection heat transfer coefficient is applied to other models,the results of the analysis and test values show good concordance.The method proposed has some limitations.
文摘Semiconductor nanowires （NW） possess several beneficial properties for efficient conversion of solar energy into electricity and chemical energy. Due to their efficient absorption of light, short distances for minority carriers to travel, high surface-to-volume ratios, and the availability of scalable synthesis methods, they provide a pathway to address the low cost-to-power requirements for widescale adaptation of solar energy conversion technologies. Here we highlight recent progress in our group towards implementation of NW components as photovoltaic and photoelectrochemical energy conversion devices. An emphasis is placed on the unique properties of these one-dimensional （1D） structures, which enable the use of abundant, low-cost materials and improved energy conversion efficiency compared to bulk devices.
基金supported by the National Natural Science Foundation of China (Grant No. 10905093)the Program for New Century Excellent Talents in University of China (Grant No. NCET-04-1006)+1 种基金the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 200136)the Natural Science Foundation for Youngsters of Naval University of Engineering (Grant No. HGDQNJJ10017)
文摘The constructal optimizations of T-shaped fin with two-dimensional heat transfer model are carried out by finite element method and taking the minimization of equivalent thermal resistance based on entransy dissipation and the minimization of maximum thermal resistance as optimization objectives, respectively. The effects of the global parameter a (integrating the coefficient of convective heat transfer, the overall area occupied by fin and its thermal conductivity) and the volume fraction ? of fin on the minimums of equivalent thermal resistance and maximum thermal resistance as well as their corresponding optimal configurations are analyzed. The comparison of the results based on the above two optimization objectives is conducted. The results show that the optimal structures based on the two optimization objectives are obviously different from each other. Compared with the optimization result by taking the minimization of maximum thermal resistance as the objective, the optimization result by taking the equivalent thermal resistance minimization as the objective can reduce the average temperature difference in the fin obviously. The increases of a and ? can all improve the working status of local hot spot and the global heat transfer performance of the system. But the improvement effects of the increases of a and ? on the minimization of equivalent thermal resistance are different from those on the minimization of maximum thermal resistance. For either objective, the effect of a is different from that of ?. The T-shaped fin with minimum equivalent thermal resistance is much taller than that with minimum maximum thermal resistance; for either optimization objective, the stem of fin is thicker than the branches of fin, and the stem thickness is relatively close to branch thickness when the minimization of equivalent thermal resistance is taken as the optimization objective. The T-shaped fin with flat stem and slender branches can benefit the reduction of the maximum thermal resistance.
文摘After Bénard＇s experiment in 1900, Rayleigh formulated heat convection problems by the Oberbeck-Boussinesq approximation in the horizontal strip domain in 1916. The pattern formations have been investigated by the bifurcation theory, weakly nonlinear theories and computational approaches. The boundary conditions for the velocity on the upper and lower boundaries are usually assumed as stress-free or no-slip. In the first part of this paper, some bifurcation pictures for the case of the stress-free on the upper boundary and the no-slip on the lower boundary are obtained. In the second part of this paper, the bifurcation pictures for the case of the stress-free on both boundaries by a computer assisted proof are verified. At last., Bénard-Marangoni heat convections for the ease of the free surface of the upper boundary are considered.
基金supported by the National 111 Project of China(Grant No.B06024)the National Basic Research Program of China("973"Project)(Grant No.2011CB610305)the National Natural Science Foundation of China(Grant No.51206128)
文摘The natural convective heat transfer performance and thermo-fluidic characteristics of honeycombs with/without chimney extensions are numerically investigated.The present numerical simulations are validated by the purposely-designed experimental measurements on honeycombs with/without chimney.Good agreement between numerical simulation and experimental measurement is obtained.The influences of inclination angle and geometric parameters such as cell shape,streamwise and spanwise length are also numerically quantified.With the increment in inclination angle,the overall heat transfer rate decreases for the honeycombs with/without chimney.For honeycombs with the same void volume fraction but different cell shapes,there is little difference on the overall heat transfer rate.To enhance the natural convective heat transfer of honeycombs,these techniques including increasing the length of honeycomb in the streamwise/spanwise direction,increasing the thermal conductivity of hon-eycomb structure or adding a chimney extension may be helpful.
