Comparison between different passive vortex generators and their stabilizing effect on Tollmien-Schlichting waves
(English)Manuscript (preprint) (Other academic)
An experimental investigation is performed on the streaky boundary layers generated by three types of vortex generators; namely cylindrical roughness elements, and miniature vortex generators (MVG) with triangular and rectangular blades. The stability of the generated streaks and the amplitude of the spanwise modulations are compared together with their efficiency to stabilize Tollmien--Schlichting (TS) waves, where the TS waves are generated upstream of the vortex generators. It is shown that for constant geometrical and boundary layer parameters the amplitude of the streaks generated by rectangular MVGs is considerably higher compared to triangular MVGs and roughness elements, even though a higher critical roughness-height Reynolds numbers is obtained for MVGs with triangular blades. In the investigated streaky boundary layers similar TS wave amplitude attenuation rates are obtained for rectangular and triangular MVGs at branch~II of the neutral stability curve whereas a higher TS wave amplitude is obtained for roughness elements compared to the two-dimensional reference boundary layer.
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-181898OAI: oai:DiVA.org:kth-181898DiVA: diva2:901350
FunderEU, European Research Council
QS 20162016-02-072016-02-072016-02-08Bibliographically approved