PIV Measurements of a Turbulent Boundary Layer Perturbed by a Wall-Mounted Transverse Circular Cylinder Element
The perturbation induced by a wall-mounted transverse circular cylinder element (TCCE) to a turbulent boundary layer (TBL) is studied using particle image velocimetry (PIV). Measurements are also performed on a smooth wall, which is used as baseline for comparison. The modification of the TBL caused by the sudden perturbation, in a statistical sense, is quantified by comparing the distributions of mean velocity, Reynolds stresses and shape factor in the two geometrical configurations. The impact of the TCCE on the TBL is found to extend more than 9 boundary-layer thickness downstream. Combining the side- and top-view PIV data indicates that the packet-like structures are stretched along the streamwise direction within a flat inclination angle when climbing over the TCCE, and retain their large spatial scales. The separated vortices induced downstream of the TCCE, are quickly lifted up to form the hairpin vortices within strong swirling strength. Then, the robust hairpin packets are generated downstream through the auto-generation scenario, which occupies the low-speed regions beneath the residual hairpin packet’s heads and impairs the process that the low-momentum fluids feed the concentrated vorticity into the residual hairpin heads. Meanwhile, the streamwise-stretched low-momentum regions (LMRs) are redeveloped in the inner layer underneath the new-generated hairpin packets. Further downstream, even though the residual hairpin packets’ heads are merged by the robust hairpin packets, they are not completely dissipated, and still interact with the new-generated hairpin packets in the outer layer to the end of the field of view.
KeywordsTurbulent boundary layer Transverse circular cylinder element Hairpin packet Low-momentum regions PIV
This work was supported by the Natural Science Foundation of China with Grant No. 11502066, 11332006, 11732010, 11572221.
This study was funded by Natural Science Foundation of China (grant number 11502066, 11332006, 11732010, 11572221).
Compliance with Ethical Standards
Conflict of interest
The authors declare that there is no conflict of interest.
- 36.Smith, C.R., Walker, J.D.A.: Sustaining mechanisms of turbulent boundary layers: the role of vortex development and interactions. In: Panton, R.L. (ed.) Proceeding of Self-Sustaining Mechanisms of Wall Turbulence. Computational Mechanics Publications, Southampton (1997)Google Scholar
- 38.Wark, C.E., Nagib, H.M.: Relation between outer structures and wall-layer events in boundary layers with and without manipulation. In: Gyr, A. (ed.) Proceeding of 2nd IUTAM Symposium on Structure of Turbulence and Drag Reduction, pp. 467–474. Springer, Zurich (1989)Google Scholar
- 43.Marusic, I., Heuer,W.: Reynolds number invariance of the structure inclination angle in wall turbulence. Phys. Rev. Lett. 99(11), 114504 (2007)Google Scholar
- 44.Kim, J., Hussain, F.: Propagation velocity and space–time correlation of perturbations in turbulent channel flow. Technical Reports (1992)Google Scholar
- 45.Christensen, K.T., Wu, Y.: Characteristics of vortex organization in the outer layer of wall turbulence. In: Fourth international symposium on turbulence and shear flow phenomena (2005)Google Scholar