Drag reduction experiment of the traveling wavy wall at high Reynolds number is conducted.A suit of traveling wavy wall device is developed.The drag forces of the traveling wavy wall with various wave speeds（c）are m...Drag reduction experiment of the traveling wavy wall at high Reynolds number is conducted.A suit of traveling wavy wall device is developed.The drag forces of the traveling wavy wall with various wave speeds（c）are measured under different water speeds（U）in the K15 cavitation water tunnel and are compared with that of the flat plate.The results show that the mean drag force of the traveling wavy wall have decreased and then increased with oscillation frequency increasing at the same flow speed.Under different flow speeds,when traveling wave wall reached to the minimum of drag force,the corresponding the ratio of the wall motion phase speed c to flow speed U,c /U is slightly different.Within the parameters of the experiment,whenc /U reaches a certain value,the drag force of the traveling wavy wall can be less than that of the flat plate.The drag reduction can be up to 42%.Furthermore,as the value ofc /U increases,the traveling wavy wall can restrain the separation and improve the quality of flow field.展开更多
Drag reduction experiments of the traveling wavy wall at high Reynolds number, ranging from 1.46×106 to 5.83×106 based on the free-stream velocity and the model length, were conducted. A suit of traveling wa...Drag reduction experiments of the traveling wavy wall at high Reynolds number, ranging from 1.46×106 to 5.83×106 based on the free-stream velocity and the model length, were conducted. A suit of traveling wavy wall device was developed and its characteristics of drag reduction at high Reynolds number were investigated. The drag forces of the traveling wavy wall with various wave speeds （ c ） were measured at different wind speeds （U ） in the FL-8 low-speed wind tunnel and compared with the drag force of the flat plate. The results show that the mean drag force of the traveling wavy wall decreases as the value of c /U increases, at different wind velocities, the values of c /U corresponding to minimal drag force of the traveling wavy wall are different, when the values of c /U are larger than 0.6, the mean drag forces of the traveling wavy wall are smaller than those of the flat plate, and the drag reduction can be up to 60%. The drag reduction effectiveness of traveling wavy wall is thus achieved. Furthermore, as the value of c /U increases, the traveling wavy wall can restrain the separation and improve the quality of flow field.展开更多
The availability of network communication services is an important evaluation standard to measure the ability of the network to meet the user’s business needs.The current related research mostly focuses on the evalua...The availability of network communication services is an important evaluation standard to measure the ability of the network to meet the user’s business needs.The current related research mostly focuses on the evaluation of network reliability,which cannot reflect the logical relationship between failure/maintenance and network performance parameters.Mobile Ad Hoc Network is a multi-hop,centerless and energy-constrained distributed system.Due to the dynamic change of communication environment and the instability of wireless link,Ad Hoc Network is facing great challenges in service availability.In this thesis,a fault-based quantitative evaluation model of traffic availability in Ad Hoc networks is proposed.By studying the multi-state Markov fault model of communication networks and the performance analysis of delay index based on CSMA\CA protocol,the quantitative evaluation of traffic availability in Ad Hoc networks is realized.And the availability of tactical unit network under different typical network configuration conditions is analyzed through experiments.展开更多
文摘Drag reduction experiment of the traveling wavy wall at high Reynolds number is conducted.A suit of traveling wavy wall device is developed.The drag forces of the traveling wavy wall with various wave speeds（c）are measured under different water speeds（U）in the K15 cavitation water tunnel and are compared with that of the flat plate.The results show that the mean drag force of the traveling wavy wall have decreased and then increased with oscillation frequency increasing at the same flow speed.Under different flow speeds,when traveling wave wall reached to the minimum of drag force,the corresponding the ratio of the wall motion phase speed c to flow speed U,c /U is slightly different.Within the parameters of the experiment,whenc /U reaches a certain value,the drag force of the traveling wavy wall can be less than that of the flat plate.The drag reduction can be up to 42%.Furthermore,as the value ofc /U increases,the traveling wavy wall can restrain the separation and improve the quality of flow field.
文摘Drag reduction experiments of the traveling wavy wall at high Reynolds number, ranging from 1.46×106 to 5.83×106 based on the free-stream velocity and the model length, were conducted. A suit of traveling wavy wall device was developed and its characteristics of drag reduction at high Reynolds number were investigated. The drag forces of the traveling wavy wall with various wave speeds （ c ） were measured at different wind speeds （U ） in the FL-8 low-speed wind tunnel and compared with the drag force of the flat plate. The results show that the mean drag force of the traveling wavy wall decreases as the value of c /U increases, at different wind velocities, the values of c /U corresponding to minimal drag force of the traveling wavy wall are different, when the values of c /U are larger than 0.6, the mean drag forces of the traveling wavy wall are smaller than those of the flat plate, and the drag reduction can be up to 60%. The drag reduction effectiveness of traveling wavy wall is thus achieved. Furthermore, as the value of c /U increases, the traveling wavy wall can restrain the separation and improve the quality of flow field.
基金We would like to acknowledge support from the Foundation of School of Computer Science and Engineering,Xi’an Technological University(gsysi2016012)the Equipment Advance Research Project(41402020202).
文摘The availability of network communication services is an important evaluation standard to measure the ability of the network to meet the user’s business needs.The current related research mostly focuses on the evaluation of network reliability,which cannot reflect the logical relationship between failure/maintenance and network performance parameters.Mobile Ad Hoc Network is a multi-hop,centerless and energy-constrained distributed system.Due to the dynamic change of communication environment and the instability of wireless link,Ad Hoc Network is facing great challenges in service availability.In this thesis,a fault-based quantitative evaluation model of traffic availability in Ad Hoc networks is proposed.By studying the multi-state Markov fault model of communication networks and the performance analysis of delay index based on CSMA\CA protocol,the quantitative evaluation of traffic availability in Ad Hoc networks is realized.And the availability of tactical unit network under different typical network configuration conditions is analyzed through experiments.
