A vorticity-velocity method was used to study the incompressible viscous fluid flow around a circular cylinder with surface suction or blowing. The resulted high order implicit difference equations were effeciently so...A vorticity-velocity method was used to study the incompressible viscous fluid flow around a circular cylinder with surface suction or blowing. The resulted high order implicit difference equations were effeciently solved by the modified incomplete LU decomposition conjugate gradient scheme ( MILU-CG). The effects of surface suction or blowing' s position and strength on the vortex structures in the cylinder wake, as well as on the drag and lift forces at Reynoldes number Re = 100 were investigated numerically. The results show that the suction on the shoulder of the cylinder or the blowing on the rear of the cylinder can effeciently suppress the asymmetry of the vortex wake in the transverse direction and greatly reduce the lift force; the suction on the shoulder of the cylinder, when its strength is properly chosen, can reduce the drag force significantly, too.展开更多
The aerodynamic characteristics are vital for short cylindrical Terminal Sensitive Bullets(TSB)with lowaspect ratio,especially in terminal trajectory.Currently,there is little research in terms of the TSB andshort cyl...The aerodynamic characteristics are vital for short cylindrical Terminal Sensitive Bullets(TSB)with lowaspect ratio,especially in terminal trajectory.Currently,there is little research in terms of the TSB andshort cylinder with two free ends,and particularly in this trajectory,where the scanning angleβand rollangle a vary over a broad range between 0°and 180.In this work wind tunnel experiments are firstconducted to learn the effects of Reynolds number and scanning angle on aerodynamic parameters forshort cylinder with aspect ratio L/D=1.Similar to infinite cylinder,for the short cylinder with two freeends,the drag crisis phenomenon still exists in the critical regime 1.7×10^(5)≤Re≤6.8×10^(5).Then 3Dsimulations are performed to demonstrate the aerodynamic characteristics of short cylinder and TSBover a broad range of Re,L/D,a and 6.The sensitivity analysis of time step and grid are presented as well.whenβ3=0,for short cylinder,the drag crisis phenomenon was also observed in the simulation,but notas obvious as in the wind tunnel test.In some attitudes,there is an obvious Karman vortexin the wake ofshort cylinder and TSB.The correlation between time-averaged aerodynamic coefficients and L/D,Re,a&l is discussed.The vortex shedding frequency and shear layer behavior are obtained for quasi-steadyand unsteady flow.Finally,the effect of end's shape on drag reduction and vortex shedding frequency isanalyzed.展开更多
基金Foundation item:the Natural Science Foundation of Jiangsu Province(BK97056109)
文摘A vorticity-velocity method was used to study the incompressible viscous fluid flow around a circular cylinder with surface suction or blowing. The resulted high order implicit difference equations were effeciently solved by the modified incomplete LU decomposition conjugate gradient scheme ( MILU-CG). The effects of surface suction or blowing' s position and strength on the vortex structures in the cylinder wake, as well as on the drag and lift forces at Reynoldes number Re = 100 were investigated numerically. The results show that the suction on the shoulder of the cylinder or the blowing on the rear of the cylinder can effeciently suppress the asymmetry of the vortex wake in the transverse direction and greatly reduce the lift force; the suction on the shoulder of the cylinder, when its strength is properly chosen, can reduce the drag force significantly, too.
基金The authors would like to acknowledge the financial supports from the National Natural Science Foundation of China(Grant No.11372136)the Special fund for basic scientific research of Central University(Grant No.30916011306)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX17_0386).
文摘The aerodynamic characteristics are vital for short cylindrical Terminal Sensitive Bullets(TSB)with lowaspect ratio,especially in terminal trajectory.Currently,there is little research in terms of the TSB andshort cylinder with two free ends,and particularly in this trajectory,where the scanning angleβand rollangle a vary over a broad range between 0°and 180.In this work wind tunnel experiments are firstconducted to learn the effects of Reynolds number and scanning angle on aerodynamic parameters forshort cylinder with aspect ratio L/D=1.Similar to infinite cylinder,for the short cylinder with two freeends,the drag crisis phenomenon still exists in the critical regime 1.7×10^(5)≤Re≤6.8×10^(5).Then 3Dsimulations are performed to demonstrate the aerodynamic characteristics of short cylinder and TSBover a broad range of Re,L/D,a and 6.The sensitivity analysis of time step and grid are presented as well.whenβ3=0,for short cylinder,the drag crisis phenomenon was also observed in the simulation,but notas obvious as in the wind tunnel test.In some attitudes,there is an obvious Karman vortexin the wake ofshort cylinder and TSB.The correlation between time-averaged aerodynamic coefficients and L/D,Re,a&l is discussed.The vortex shedding frequency and shear layer behavior are obtained for quasi-steadyand unsteady flow.Finally,the effect of end's shape on drag reduction and vortex shedding frequency isanalyzed.
