The Effect of Attached Manipulator Ring on a Fully Developed Turbulent Pipe Flow
The response of a fully developed pipe flow to an attached ring-type manipulator with rectangular cross section was investigated by measuring the mean velocity profiles. The ring-type element has a height of 0.14 times the pipe radius and was positioned rigidly in a 99.8 mm diameter，smooth-walled，circular pipe in which air was flowing at Reynolds number of 6.2 x 10^4. The results indicated that the flow was significantly perturbed by the manipulator ring and the return of the flow to a self-preserving state without disturbance was achieved either at about 960 times the manipulator height or at about 67 times the pipe diameter. Furthermore，near the reattachment point，which was about 8.2 times the manipulator height from that tip，the mean velocity profile in the core region of the pipe was much more uniform and the velocity gradient was steeper near the wall than a fully developed turbulent flow，indicating enhanced mixing. The boundary layer characteristics，such as the skin friction coefficient and boundary layer thickness，were also altered in the streamwise direction upon a pulsewise disturbance.