Modification of Turbulent Boundary Layer Flow by Local Wall Vibration
Abstract
The objective of the present study is to investigate the modification of turbulent boundary layer flow by local wall vibration. With a wall-deformation actuator, the wall locally vibrates up and down at the frequencies of 10 ~ 150 Hz, where 50 Hz is the bursting frequency at the experimental condition. The diameter of the wall actuator is D= 20 mm (600 wall units) and the amplitude of the wall vibration is 2 mm (60 wall units) at f=100 Hz. Simultaneous measurements of the streamwise velocity in the spanwise direction are performed at several wall-normal and streamwise locations. The mean streamwise velocity decreases in most places due to the wall vibration, but increases very near the wall and near the actuator. This is due to the motion induced by the streamwise vortices which are generated by the vibrating wall. A two-dimensional numerical simulation indicates that two different streamwise vortical structures are generated, respectively, when the vibrating wall reaches top and bottom ends. The streamwise velocity fluctuations significantly increase in most places but decrease very near the wall. Two-point correlations of the streamwise velocity in the spanwise direction show that flow structures of about 1D size are generated by the wall vibration. Flow visualization results using the smoke-wire technique will be shown in the final presentation.
- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- November 2000
- Bibcode:
- 2000APS..DFD.MA008K