Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the aut...Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.展开更多
Testing centrifugal fan flow field by physical laboratory is difficult because the testing system is complex and the workload is heavy, and the results observed by naked-eye deviates far from the actual value. To addr...Testing centrifugal fan flow field by physical laboratory is difficult because the testing system is complex and the workload is heavy, and the results observed by naked-eye deviates far from the actual value. To address this problem, the computational fluid dynamics software FLUENT was applied to establish three-dimensional model of the centrifugal fan. The numeral model was verified by comparing simulation data to experimental data. The pressure centrifugal fan and the speed changes in distribution in centrifugal fan was simulated by computational fluid dynamics soft-ware FLUENT. The simulation results show that the gas flow velocity in the impeller increases with impeller radius increase. Static pressure gradually increases when gas from the fan access is imported through fan impeller leaving fans.展开更多
Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their rela-tionship with turbulence properties in a stirred tank of 0.48 m diameter,agitated by four different disc turbines...Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their rela-tionship with turbulence properties in a stirred tank of 0.48 m diameter,agitated by four different disc turbines,in-cluding Rushton turbine,concaved blade disk turbine,half elliptical blade disk turbine,and parabolic blade disk turbine.Phase-averaged and phase-resolved flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail.The location,size and strength of vortices were determined by the simplified λ2-criterion and the results showed that the blade shape had great effect on the trailing vortex characteristics.The larger curvature resulted in longer residence time of the vortex at the impeller tip,bigger distance between the upper and lower vortices and longer vortex life,also leads to smaller and stronger vortices.In addition,the turbulent ki-netic energy and turbulent energy dissipation in the discharge flow were determined and discussed.High turbulent kinetic energy and turbulent energy dissipation regions were located between the upper and lower vortices and moved along with them.Although restricted to single phase flow,the presented results are essential for reliable de-sign and scale-up of stirred tank with disc turbines.展开更多
Experimental study is performed to design and develop a cylindrical micro-pump driven by expansion and contraction of the heat deformation material, whose variation is caused with the aid of heating and cooling proper...Experimental study is performed to design and develop a cylindrical micro-pump driven by expansion and contraction of the heat deformation material, whose variation is caused with the aid of heating and cooling properties of Peltier devices. The pump consists of the diffuser valve unit, the heat deformation material unit, the nozzle valve unit, the Peltier devices and the cover. The input current of the Peltier devices is controlled by the bipolar power supply so that the Peltier devices are heated and cooled periodically. The working fluid flow in the micro-pump is caused by the periodical thermal deformation of material which is caused by the periodical heating and cooling of the Peltier devices. In order to measure the fluid flow in the micro-pump, micro air bubbles are employed as a tracer. The corresponding movement is recorded by X-ray apparatus and its velocity is measured by PIV （particle image velocimetry）. It is found that, the micro-pump developed here can make the working fluid flow. The corresponding fluid flow in the micro pump is confirmed by the numerical method.展开更多
Fishes that use undulatory locomotion occasionally change their inherent kinematics in terms of some natural behavior.This special locomotion pattern was vividly dubbed "hybrid kinematics" by biologists rece...Fishes that use undulatory locomotion occasionally change their inherent kinematics in terms of some natural behavior.This special locomotion pattern was vividly dubbed "hybrid kinematics" by biologists recently.In this paper,we employed a physical model with body shape of a Mackerel(Scomber scombrus),to use the three most typical undulatory kinematics:anguillform,carangiform and thunniform,to investigate the hydrodynamic performance of the so-called "hybrid kinematics" biological issue.Theoretical models of both kinematics and hydrodynamics of the physical model swimming were developed.Base on this model,the instantaneous force produced by fish undulatory body and flapping tail were calculated separately.We also quantitatively measured the hydrodynamic variables of the robotic model swimming with the three undulatory kinematics on an experimental apparatus.The results of both theoretical model and experiment showed that the robot with thunniform kinematics not only reaches a higher speed but also is more efficient during steady swimming mode.However,anguilliform kinematics won the speed race during the initial acceleration.Additionally,the digital particle image velocimetry(DPIV) results showed some difference of the wake flow generated by the robotic swimmer among the three undulatory kinematics.Our findings may possibly shed light on the motion control of a biomimetic robotic fish and provide certain evidence of why the "hybrid kinematics" exists within the typical undulatory locomotion patterns.展开更多
In this paper,the internal flow field in a centrifugal pump working at the design flow rate operating condition has been measured using the particle image velocimetry(PIV)technique with the fluorescent particles and t...In this paper,the internal flow field in a centrifugal pump working at the design flow rate operating condition has been measured using the particle image velocimetry(PIV)technique with the fluorescent particles and the index-matched fluid technology.The index-marching fluid with the same refractive index as the transparent material has been prepared and applied in the present test of pump with geometrical complex walls.The comparison between velocity distributions of PIV results both with and without fluorescent particles,as well as with and without index-marching fluid are conducted to find the differences.The DES(Detached Eddy Simulation)has been employed to calculate the three-dimensional unsteady turbulent flow in the pump to examine and to certify the PIV measurement results.The DES results of instantaneous flow velocity fields agree with PIV test results with fluorescent particles and index-marching fluid.It is necessary to perform the PIV measurement of pumps with fluorescent seeds and index-marching fluid in order to get exact results.The experimental results show the distributions of velocity,steamlines,and the principal Reynolds normal stress(PRNS)and the principal Reynolds shear stress(PRSS).展开更多
Volumetric particle image velocimetry(VPIV) refers to a PIV-based technique which can obtain full velocity components in a three-dimensional measurement volume.A new VPIV method with a single lens was developed.A thre...Volumetric particle image velocimetry(VPIV) refers to a PIV-based technique which can obtain full velocity components in a three-dimensional measurement volume.A new VPIV method with a single lens was developed.A three-vision prism was used to make viewing from different angles using one camera.The technique was tested and successfully applied to a three-dimensional three-component(3D3C) measurement of a zero-net-mass-flux jet flow.The accuracy of the measurement was investigated,specifically in steps of calibration,self-calibration and particle triangulation.Time sequence of a vortex ring development was presented.It was shown that the measurement has high accuracy with validation rate of velocity vector reaching about 95%.The flow with vortex ring passing the measurement volume was studied using both swirl strength and vorticity magnitude criteria.Through comparison,the swirl criterion was found to be superior to the criterion of vorticity in differentiating the rotation motion and the free shear.展开更多
Blood pumps have been adopted to treat heart failure over the past decades. A novel blood pump adopting the rotor with splitter blades and tandem cascade stator was developed recently. A particle image velocimetry （...Blood pumps have been adopted to treat heart failure over the past decades. A novel blood pump adopting the rotor with splitter blades and tandem cascade stator was developed recently. A particle image velocimetry （P1V） experiment was carried out to verify the design of the blood pump based on computational fluid dynamics （CFD） and further analyze the flow properties in the rotor and stator. The original sized pump model with an acrylic housing and an experiment loop were constructed to perform the optical measurement. The PIV testing was carried out at the rotational speed of 6952±50 r/rain with the flow rate of 3.1 l/rain and at 8186±50 r/min with 3.5 l/rain, respectively. The velocity and the Reynolds shear stress distributions were investigated by PIV and CFD, and the comparisons between them will be helpful for the future blood pump design.展开更多
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant Nos. 41176074, 51379043 and 51409063）Acknowledgement This project was supported by the National Natural Science Foundation of China （Grant Nos. 41176074,51379043 and 51409063） and was conducted in response to the great support received from a basic research project entitled ＂Multihull Ship Technology Key Laboratory of Fundamental Science for National Defence＂, which was conducted at Harbin Engineering University. The authors would like to extend their sincere gratitude to their colleagues in the towing tank laboratory.
文摘Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.
文摘Testing centrifugal fan flow field by physical laboratory is difficult because the testing system is complex and the workload is heavy, and the results observed by naked-eye deviates far from the actual value. To address this problem, the computational fluid dynamics software FLUENT was applied to establish three-dimensional model of the centrifugal fan. The numeral model was verified by comparing simulation data to experimental data. The pressure centrifugal fan and the speed changes in distribution in centrifugal fan was simulated by computational fluid dynamics soft-ware FLUENT. The simulation results show that the gas flow velocity in the impeller increases with impeller radius increase. Static pressure gradually increases when gas from the fan access is imported through fan impeller leaving fans.
基金Supported by the National Natural Science Foundation of China（20776008 20821004 20990224） the National Basic Research Program of China（2007CB714300）
文摘Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their rela-tionship with turbulence properties in a stirred tank of 0.48 m diameter,agitated by four different disc turbines,in-cluding Rushton turbine,concaved blade disk turbine,half elliptical blade disk turbine,and parabolic blade disk turbine.Phase-averaged and phase-resolved flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail.The location,size and strength of vortices were determined by the simplified λ2-criterion and the results showed that the blade shape had great effect on the trailing vortex characteristics.The larger curvature resulted in longer residence time of the vortex at the impeller tip,bigger distance between the upper and lower vortices and longer vortex life,also leads to smaller and stronger vortices.In addition,the turbulent ki-netic energy and turbulent energy dissipation in the discharge flow were determined and discussed.High turbulent kinetic energy and turbulent energy dissipation regions were located between the upper and lower vortices and moved along with them.Although restricted to single phase flow,the presented results are essential for reliable de-sign and scale-up of stirred tank with disc turbines.
文摘Experimental study is performed to design and develop a cylindrical micro-pump driven by expansion and contraction of the heat deformation material, whose variation is caused with the aid of heating and cooling properties of Peltier devices. The pump consists of the diffuser valve unit, the heat deformation material unit, the nozzle valve unit, the Peltier devices and the cover. The input current of the Peltier devices is controlled by the bipolar power supply so that the Peltier devices are heated and cooled periodically. The working fluid flow in the micro-pump is caused by the periodical thermal deformation of material which is caused by the periodical heating and cooling of the Peltier devices. In order to measure the fluid flow in the micro-pump, micro air bubbles are employed as a tracer. The corresponding movement is recorded by X-ray apparatus and its velocity is measured by PIV （particle image velocimetry）. It is found that, the micro-pump developed here can make the working fluid flow. The corresponding fluid flow in the micro pump is confirmed by the numerical method.
基金supported by the National Natural Science Foundation of China (Grant No. 61075100)
文摘Fishes that use undulatory locomotion occasionally change their inherent kinematics in terms of some natural behavior.This special locomotion pattern was vividly dubbed "hybrid kinematics" by biologists recently.In this paper,we employed a physical model with body shape of a Mackerel(Scomber scombrus),to use the three most typical undulatory kinematics:anguillform,carangiform and thunniform,to investigate the hydrodynamic performance of the so-called "hybrid kinematics" biological issue.Theoretical models of both kinematics and hydrodynamics of the physical model swimming were developed.Base on this model,the instantaneous force produced by fish undulatory body and flapping tail were calculated separately.We also quantitatively measured the hydrodynamic variables of the robotic model swimming with the three undulatory kinematics on an experimental apparatus.The results of both theoretical model and experiment showed that the robot with thunniform kinematics not only reaches a higher speed but also is more efficient during steady swimming mode.However,anguilliform kinematics won the speed race during the initial acceleration.Additionally,the digital particle image velocimetry(DPIV) results showed some difference of the wake flow generated by the robotic swimmer among the three undulatory kinematics.Our findings may possibly shed light on the motion control of a biomimetic robotic fish and provide certain evidence of why the "hybrid kinematics" exists within the typical undulatory locomotion patterns.
基金supported by the National Natural Science Foundation of China(Grant No.10532010)
文摘In this paper,the internal flow field in a centrifugal pump working at the design flow rate operating condition has been measured using the particle image velocimetry(PIV)technique with the fluorescent particles and the index-matched fluid technology.The index-marching fluid with the same refractive index as the transparent material has been prepared and applied in the present test of pump with geometrical complex walls.The comparison between velocity distributions of PIV results both with and without fluorescent particles,as well as with and without index-marching fluid are conducted to find the differences.The DES(Detached Eddy Simulation)has been employed to calculate the three-dimensional unsteady turbulent flow in the pump to examine and to certify the PIV measurement results.The DES results of instantaneous flow velocity fields agree with PIV test results with fluorescent particles and index-marching fluid.It is necessary to perform the PIV measurement of pumps with fluorescent seeds and index-marching fluid in order to get exact results.The experimental results show the distributions of velocity,steamlines,and the principal Reynolds normal stress(PRNS)and the principal Reynolds shear stress(PRSS).
基金supported by the National Natural Science Foundation of China (Grant Nos. 11102013,10832001)the "Weishi" Foundation of Beijing University of Aeronautics and Astronautics (Grant No. YWF-12-RHRS-008)
文摘Volumetric particle image velocimetry(VPIV) refers to a PIV-based technique which can obtain full velocity components in a three-dimensional measurement volume.A new VPIV method with a single lens was developed.A three-vision prism was used to make viewing from different angles using one camera.The technique was tested and successfully applied to a three-dimensional three-component(3D3C) measurement of a zero-net-mass-flux jet flow.The accuracy of the measurement was investigated,specifically in steps of calibration,self-calibration and particle triangulation.Time sequence of a vortex ring development was presented.It was shown that the measurement has high accuracy with validation rate of velocity vector reaching about 95%.The flow with vortex ring passing the measurement volume was studied using both swirl strength and vorticity magnitude criteria.Through comparison,the swirl criterion was found to be superior to the criterion of vorticity in differentiating the rotation motion and the free shear.
基金supported by the National Natural Science Foundation of China (Grant Nos.50676004 and 50736007)the Science Foundation of Fuwai hospital (Grant No:2009F-010)the Key Subject Foundation of Beijing:Fluid Machinery and Engineering
文摘Blood pumps have been adopted to treat heart failure over the past decades. A novel blood pump adopting the rotor with splitter blades and tandem cascade stator was developed recently. A particle image velocimetry （P1V） experiment was carried out to verify the design of the blood pump based on computational fluid dynamics （CFD） and further analyze the flow properties in the rotor and stator. The original sized pump model with an acrylic housing and an experiment loop were constructed to perform the optical measurement. The PIV testing was carried out at the rotational speed of 6952±50 r/rain with the flow rate of 3.1 l/rain and at 8186±50 r/min with 3.5 l/rain, respectively. The velocity and the Reynolds shear stress distributions were investigated by PIV and CFD, and the comparisons between them will be helpful for the future blood pump design.
