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
The characteristics of the dual bluff body vortex shedding is investigated, and the possibility to use dual bluff body combinations to strengthen the hydrodynamic vibration around the bluff body objects is explored. T...The characteristics of the dual bluff body vortex shedding is investigated, and the possibility to use dual bluff body combinations to strengthen the hydrodynamic vibration around the bluff body objects is explored. The numerical and experimental approaches were utilized to examine the time dependent flow field and the pressure oscillation around the bluff bodies. The numerical data were obtained by the advanced large eddy simulation model. The experiment was conducted on a laboratory scale of Karman vortex flowmeter with 40 mm diameter. It is revealed that the optimized dual bluff body combinations strengthened the hydrodynamic vibration. It was also found that the hydrodynamic vibration with 180° phase difference occurred at the axisymmetric points of circular pipe on the lateral faces of the equilateral triangle-section bluff bodies. Using the dual bluff body configuration and the differential sensing technique, a novel prototype of vortex flowmeter with excellent noise immunity and improved sensibility was developed.展开更多
Vortex diode,as an important component in power fluidics,has been used in nuclear reprocessing engineering where it is desirable to avoid pumps with moving parts.The performance of the fluidic system depends on the ma...Vortex diode,as an important component in power fluidics,has been used in nuclear reprocessing engineering where it is desirable to avoid pumps with moving parts.The performance of the fluidic system depends on the matched design parameters of vortex diodes and the supporting facilities.However,no clear guidelines for design and optimization of vortex diodes system are available.Therefore,we carried out detailed experimental study on hydraulic characteristics of the vortex diodes system with changeable parameters to evolve such guidelines.The study covered a wide range of a vortex diode and vortex diodes system.The variation of averaged discharge and volumetric efficiency in respect to air supply pressure,liquid level of water tank and liquid level stroke of gas-liquid energy converter was studies.The experimental results were analyzed to develop design guidelines.The guidelines are shown to be useful for obtaining the design parameters that would yield the desired hydrau- lic performance for the required operating conditions.展开更多
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.
基金Supported by the National Natural Science Foundation of China (No. 59835160) and Scientific Research Foundation of State Education Ministry for Returned Overseas Chinese Scholars.
文摘The characteristics of the dual bluff body vortex shedding is investigated, and the possibility to use dual bluff body combinations to strengthen the hydrodynamic vibration around the bluff body objects is explored. The numerical and experimental approaches were utilized to examine the time dependent flow field and the pressure oscillation around the bluff bodies. The numerical data were obtained by the advanced large eddy simulation model. The experiment was conducted on a laboratory scale of Karman vortex flowmeter with 40 mm diameter. It is revealed that the optimized dual bluff body combinations strengthened the hydrodynamic vibration. It was also found that the hydrodynamic vibration with 180° phase difference occurred at the axisymmetric points of circular pipe on the lateral faces of the equilateral triangle-section bluff bodies. Using the dual bluff body configuration and the differential sensing technique, a novel prototype of vortex flowmeter with excellent noise immunity and improved sensibility was developed.
基金supported by the National Natural Science Foundation of China(Grant No.51006087)
文摘Vortex diode,as an important component in power fluidics,has been used in nuclear reprocessing engineering where it is desirable to avoid pumps with moving parts.The performance of the fluidic system depends on the matched design parameters of vortex diodes and the supporting facilities.However,no clear guidelines for design and optimization of vortex diodes system are available.Therefore,we carried out detailed experimental study on hydraulic characteristics of the vortex diodes system with changeable parameters to evolve such guidelines.The study covered a wide range of a vortex diode and vortex diodes system.The variation of averaged discharge and volumetric efficiency in respect to air supply pressure,liquid level of water tank and liquid level stroke of gas-liquid energy converter was studies.The experimental results were analyzed to develop design guidelines.The guidelines are shown to be useful for obtaining the design parameters that would yield the desired hydrau- lic performance for the required operating conditions.
