Plasma Synthetic Jet(PSJ) actuators have shown wide and promising application prospects in high-speed flow control, due to their advantages including high exhaust speed, wide frequency band, rapid response, and non-mo...Plasma Synthetic Jet(PSJ) actuators have shown wide and promising application prospects in high-speed flow control, due to their advantages including high exhaust speed, wide frequency band, rapid response, and non-moving components. Although previous studies on PSJ actuators are abundant, most of them have focused on the performance of a single actuator. However, in practice, an actuator array is very necessary for large-scale aerodynamic actuation on account of the small affected area of a single PSJ. In this paper, the characteristics of a twoelectrode plasma synthetic jet actuator array in serial are investigated experimentally. Compared to a parallel actuator array, the serial actuator array requires simpler power supply design and is much easier to realize. High-speed photography of the discharge evolution, voltage-current measurement, and shadowgraphy visualization are used in the investigation. Experimental results show that, for the serial actuator array, weak discharges happen firstly between energized and suspending electrodes, and then a strong pulse arc discharge is triggered. The breakdown voltage in serial is irrelevant to such factors as the number of actuators, the maximum or minimum gap in serial,the connection sequence, etc. It is mainly determined by the sum of gaps. For serial actuators with the same anode-to-cathode spacing, the energy deposition is the same, and the jet is synchronous and similar. Because of the entrainment and merging of adjacent jet vortices, the jet front speed of an aligned synchronous jet array increases as the orifice distance decreases. To achieve the highest jet front velocity, the orifice of the actuator has an optimal diameter.展开更多
A 15° swept wing with dielectric barrier discharge plasma actuator is designed. Experimental study of flow separation control with nanosecond pulsed plasma actuation is performed at flow velocity up to 40 m/s. Th...A 15° swept wing with dielectric barrier discharge plasma actuator is designed. Experimental study of flow separation control with nanosecond pulsed plasma actuation is performed at flow velocity up to 40 m/s. The effects of the actuation frequency and voltage on the aerodynamic performance of the swept wing are evaluated by the balanced force and pressure measurements in the wind tunnel. At last, the performances on separation flow control of the three types of actuators with plane and saw-toothed exposed electrodes are compared. The optimal actua- tion frequency for the flow separation control on the swept wing is detected, namely the reduced frequency is 0.775, which is different from 2-D airfoil separation control. There exists a threshold voltage for the low swept wing flow control. Before the threshold voltage, as the actuation voltage increases, the control effects become better. The maximum lift is increased by 23.1% with the drag decreased by 22.4% at 14°, compared with the base line. However, the best effects are obtained on actuator with plane exposed electrode in the low-speed experiment and the abilities of saw-toothed actuators are expected to be verified under high-speed conditions.展开更多
OBJECTIVE:To analyze the Doppler ultrasound blood flow of Renying(carotid artery)pulse,Cunkou(radial artery)pulse,and Fuyang(anterior tibial artery)pulse in the normal group and the functional constipation with gastro...OBJECTIVE:To analyze the Doppler ultrasound blood flow of Renying(carotid artery)pulse,Cunkou(radial artery)pulse,and Fuyang(anterior tibial artery)pulse in the normal group and the functional constipation with gastrointestinal heat(FCGH)group,and to compare and explore the differences of Renying,Cunkou and Fuyang pulses.METHODS:Sixty normal subjects and 60 patients with gastrointestinal heat constipation were collected in the department of ultrasound,Beijing Anzhen Hospital,Capital Medical University.Doppler ultrasound was used to observe the blood flow indexes including maximum systolic velocity(Vp),maximum diastolic velocity(Vd),mean velocity(Vm),pulse index(PI),resistance index(RI),vascular diameter(D),and circulation blood flow cycle(ET)of Renying pulse,Cunkou pulse and Fuyang pulse in the normal group and patients with gastrointestinal heat constipation.The differences of these three pulses were compared between the normal group and the FCGH group.RESULTS:The PI,Vp,Vm,RI,and D of the three pulses in the normal group were statistically significant different(P<0.01).In the comparison of Doppler flow diagram of three pulses in the FCGH group,there were significant differences in PI,Vd,Vp,Vm,RI,and D(P<0.01).CONCLUSION:Under normal conditions,the indexes of Renying pulse Doppler flow diagram,Cunkou pulse Doppler flow diagram,and Fuyang pulse Doppler flow diagram are significantly different.In the FCGH group,most of the indexes of Renying pulse Doppler flow diagram,Cunkou pulse Doppler flow diagram,and Fuyang pulse Doppler flow diagram are different.This result verified the necessity of simultaneous examinations of all Renying,Cunkou,and Fuyang pulses in modern Chinese medicine.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11372349,11502295,and11572349)
文摘Plasma Synthetic Jet(PSJ) actuators have shown wide and promising application prospects in high-speed flow control, due to their advantages including high exhaust speed, wide frequency band, rapid response, and non-moving components. Although previous studies on PSJ actuators are abundant, most of them have focused on the performance of a single actuator. However, in practice, an actuator array is very necessary for large-scale aerodynamic actuation on account of the small affected area of a single PSJ. In this paper, the characteristics of a twoelectrode plasma synthetic jet actuator array in serial are investigated experimentally. Compared to a parallel actuator array, the serial actuator array requires simpler power supply design and is much easier to realize. High-speed photography of the discharge evolution, voltage-current measurement, and shadowgraphy visualization are used in the investigation. Experimental results show that, for the serial actuator array, weak discharges happen firstly between energized and suspending electrodes, and then a strong pulse arc discharge is triggered. The breakdown voltage in serial is irrelevant to such factors as the number of actuators, the maximum or minimum gap in serial,the connection sequence, etc. It is mainly determined by the sum of gaps. For serial actuators with the same anode-to-cathode spacing, the energy deposition is the same, and the jet is synchronous and similar. Because of the entrainment and merging of adjacent jet vortices, the jet front speed of an aligned synchronous jet array increases as the orifice distance decreases. To achieve the highest jet front velocity, the orifice of the actuator has an optimal diameter.
基金founded by National Natural Science Foundation of China under contract Nos. 51336011, 51276197, and 51207169
文摘A 15° swept wing with dielectric barrier discharge plasma actuator is designed. Experimental study of flow separation control with nanosecond pulsed plasma actuation is performed at flow velocity up to 40 m/s. The effects of the actuation frequency and voltage on the aerodynamic performance of the swept wing are evaluated by the balanced force and pressure measurements in the wind tunnel. At last, the performances on separation flow control of the three types of actuators with plane and saw-toothed exposed electrodes are compared. The optimal actua- tion frequency for the flow separation control on the swept wing is detected, namely the reduced frequency is 0.775, which is different from 2-D airfoil separation control. There exists a threshold voltage for the low swept wing flow control. Before the threshold voltage, as the actuation voltage increases, the control effects become better. The maximum lift is increased by 23.1% with the drag decreased by 22.4% at 14°, compared with the base line. However, the best effects are obtained on actuator with plane exposed electrode in the low-speed experiment and the abilities of saw-toothed actuators are expected to be verified under high-speed conditions.
基金Supported by the Fundamental Research Funds for the Central Public Welfare Research Institutes:Theoretical Study of Combination of of Facial Color and Pulses Mode in Traditional Chinese Medicine(No.KJ-202013),Objective Study of“Wei Qi”in Pulse Based on Color Doppler Flow Imaging(CDFI)Technology(No.YZ-202124)。
文摘OBJECTIVE:To analyze the Doppler ultrasound blood flow of Renying(carotid artery)pulse,Cunkou(radial artery)pulse,and Fuyang(anterior tibial artery)pulse in the normal group and the functional constipation with gastrointestinal heat(FCGH)group,and to compare and explore the differences of Renying,Cunkou and Fuyang pulses.METHODS:Sixty normal subjects and 60 patients with gastrointestinal heat constipation were collected in the department of ultrasound,Beijing Anzhen Hospital,Capital Medical University.Doppler ultrasound was used to observe the blood flow indexes including maximum systolic velocity(Vp),maximum diastolic velocity(Vd),mean velocity(Vm),pulse index(PI),resistance index(RI),vascular diameter(D),and circulation blood flow cycle(ET)of Renying pulse,Cunkou pulse and Fuyang pulse in the normal group and patients with gastrointestinal heat constipation.The differences of these three pulses were compared between the normal group and the FCGH group.RESULTS:The PI,Vp,Vm,RI,and D of the three pulses in the normal group were statistically significant different(P<0.01).In the comparison of Doppler flow diagram of three pulses in the FCGH group,there were significant differences in PI,Vd,Vp,Vm,RI,and D(P<0.01).CONCLUSION:Under normal conditions,the indexes of Renying pulse Doppler flow diagram,Cunkou pulse Doppler flow diagram,and Fuyang pulse Doppler flow diagram are significantly different.In the FCGH group,most of the indexes of Renying pulse Doppler flow diagram,Cunkou pulse Doppler flow diagram,and Fuyang pulse Doppler flow diagram are different.This result verified the necessity of simultaneous examinations of all Renying,Cunkou,and Fuyang pulses in modern Chinese medicine.
