Drag reduction in turbulent channel flow with periodically arrayed heating and cooling strips

作者：Yoon HS^*; El Samni OA; Chun HH

来源：Physics of Fluids, 2006, 18(2): 025104.

DOI：10.1063/1.2171196

A new technique giving significant drag reduction in turbulent shear flows has been proposed by using the buoyancy effect to generate periodic spanwise motion. Such spanwise motion can be obtained by arranging heating and cooling strips periodically aligned in the spanwise direction of a vertical channel, where the streamwise mean flow is perpendicular to the gravity vector. The strip size has been changed in order to obtain the optimum size corresponding to the maximum drag reduction. Series of direct numerical simulation have been performed where the bulk Reynolds number, Re-m=U-m delta/nu is fixed at 2270 whereas the Grashof number is changed to between 10(6) and 10(7). At the lowest Grashof number, the buoyancy forces are not strong enough to disturb the flow and no apparent variation of drag compared to the plane channel is observed. However, as the Grashof number increases, considerable drag reduction can be obtained. At the highest Grashof number, an optimum strip size of about 250 wall units gives drag reduction of about 35%. The greater the Grashof number, the smaller the strip size which attains the maximum drag reduction. The similarity between the induced lateral motions by the buoyancy forces and those induced by the spanwise wall oscillations is highlighted.

• 出版日期2006-2