EFFECT OF LONGITUDINAL VORIICES ON THE TURBULENT STRUCTURE IN NEAR-WALL REGION
纵向涡对近壁湍流结构的影响

The effect of longitudinal vortices on the turbulent structure of near-wall regionWas investigated with hydrogen bubble technique in a rectangular duct A wider high-speedstreak appears in the downwash region of vortex(where secondary flow is directed towardsthe wall),the flow is stable and the streamwise velocity is higher inside the streak)a regionincluding low-speed streaks is shown in the upwash part of vortex (where the secondaryflow is directed away from the wall),the flow structure is complicated and the strealnwisevelocity is lower.Due to the action of longitudinal vortices, the flow with higher velocityin the downwash region moves towards the wall,while the flow with lower velocity in theupwash region moves away from the wall.