Accepted Talks Proceedings »

Skin-friction drag reduction - Now with reinforced passive control

PDF
1.0MB

It is well known that the skin-friction coefficient can increase by an order of magnitude in a turbulent boundary layer compared to a laminar one at high enough Reynolds numbers. This mechanism leads to a delay of the transition to turbulence, and plays an important role in reducing the skin-friction drag on any aerodynamically smooth body. The conventional belief regarding
the stability of wall bounded shear flows is that it highly correlates with the roughness of the surface in contact with the fluid, i.e. the smoother the surface, the longer it will remain laminar. However, recent investigations have shown that well designed roughness elements, if mounted on the surface in the boundary layer, can control the flow and delay the transition to turbulence by modulating the base flow in the spanwise direction. In the present study, the transition delay result using one miniature vortex generators (MVG) array, reported in Shahinfar et. al, was repeated and successfully confirmed. In addition, by mounting a second set of MVGs downstream of the first array and reinforcing the streak amplitude, it is shown that the transition onset could successfully be pushed even further downstream.

Author(s):

[CANCELLED]    

Sohrab S. Sattarzadeh    
Linné Flow Centre, KTH Mechanics
Sweden

Jens H. M. Fransson    
Linné Flow Centre, KTH Mechanics
Sweden

Bengt E. G. Fallenius    
Linné Flow Centre, KTH Mechanics
Sweden

Alessandro Talamelli    
Linné Flow Centre, KTH Mechanics
Sweden