摘要
研究壁面有周期性定向抽吸－引射且在壁面上形成纵向速度的二维渠道流动,壁面上的纵向平均速度为〈uω〉．数值结果表明,抽吸－引射的传质倾角θ对流场的性质和壁面上的切应力等有重要的影响．与速度为〈uω〉的运动壁无扰动流动相比,它的阻力偏低,这种阻力偏低与流场的扰动特性有关,即与扰动速度分量的二重相关积分I成正比．阻力在θ＞-24°的范围内有减阻效果;能量在θ＞8°时有净能量减小的效果．
The channel flow with vectored periodic suction-injection which form longitudinalvelocity component on the wall is described. The average longitudinal velocity is (uω) and themass transfer angle for which the positive average velocity comes into being is positive.The computed velocity in flow field can be separated into a spatial average along x and a periodicdisturbance around it. Double correlation of disturbance components involves their magnitudesand phase relation, so it is characteristic of the disturbance field. A relation between change of dragcoefficient on the wall and a double correlation integral of disturbance components in flow fieldis derived for laminar flow, it provides a theoretical basis for analyzing and examining numericalresults.Numerical results show that vectored mass transfer angle has important effects on propertiesin flow field and shear stress distribution on the wall. When average longitudinal velocity (uω)is formed, compared with unperturbed fixed channel flow, the change of drag is composed of twoparts: one is the same as in the unperturbed channel flow for which the wall moves with the samevelocity (uω); the other is correlated with the properties of disturbance field, i.e. it is proportionalto the integral of double correlation of disturbance components. As the integral is negative atpresent, the second part causes the drag to decrease. The effect of drag reduction can be obtainedin the range of mass transfer angles from -24° to 90° and maximum effect can be reached whenthe angle is larger than 45°. The change of energy includes that of the energy required to drivethe main flow through the Channel and the work done by shear stress and disturbed pressure onthe wall. Because of positive average longitudinal velocity (uω) the net energy reduction can beachieved when the mass transfer angle is larger than 8°.
出处
《力学学报》
EI
CSCD
北大核心
2002年第3期439-444,共6页
Chinese Journal of Theoretical and Applied Mechanics
