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
This study focuses on the characteristics of low Reynolds number flow around airfoil of high-altitude unmanned aerial vehicles（HAUAVs） cruising at low speed.Numerical simulation on the flows around several represent...This study focuses on the characteristics of low Reynolds number flow around airfoil of high-altitude unmanned aerial vehicles（HAUAVs） cruising at low speed.Numerical simulation on the flows around several representative airfoils is carried out to investigate the low Reynolds number flow.The water tunnel model tests further validate the accuracy and effectiveness of the numerical method.Then the effects of the relative thickness of airfoil on aerodynamic performance are explored, using the above numerical method, by simulating flows around airfoils of different relative thicknesses（12%, 14%, 16%, 18%）, as well as different locations of the maximum relative thickness（x/c = 22%, 26%, 30%, 34%）, at a low Reynolds number of 5 × 10^5.Results show that performance of airfoils at low Reynolds number is mainly affected by the laminar separation bubble.On the premise of good stall characteristics, the value of maximum relative thickness should be as small as possible, and the location of the maximum relative thickness ought to be closer to the trailing edge to obtain fine airfoil performance.The numerical method is feasible for the simulation of low Reynolds number flow.The study can help to provide a basis for the design of low Reynolds number airfoil.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This study focuses on the characteristics of low Reynolds number flow around airfoil of high-altitude unmanned aerial vehicles（HAUAVs） cruising at low speed.Numerical simulation on the flows around several representative airfoils is carried out to investigate the low Reynolds number flow.The water tunnel model tests further validate the accuracy and effectiveness of the numerical method.Then the effects of the relative thickness of airfoil on aerodynamic performance are explored, using the above numerical method, by simulating flows around airfoils of different relative thicknesses（12%, 14%, 16%, 18%）, as well as different locations of the maximum relative thickness（x/c = 22%, 26%, 30%, 34%）, at a low Reynolds number of 5 × 10^5.Results show that performance of airfoils at low Reynolds number is mainly affected by the laminar separation bubble.On the premise of good stall characteristics, the value of maximum relative thickness should be as small as possible, and the location of the maximum relative thickness ought to be closer to the trailing edge to obtain fine airfoil performance.The numerical method is feasible for the simulation of low Reynolds number flow.The study can help to provide a basis for the design of low Reynolds number airfoil.
