Effect of freestream turbulence on roughness-induced crossflow instability
2013 (English)Report (Other academic)
The effect of freestream turbulence on generation of crossflow disturbances over swept wings is investigated through direct numerical simulations. The set up follows the experiments performed by Downs et al. in their TAMU experi- ment. In this experiment the authors use ASU(67)-0315 wing geometry which promotes growth of crossflow disturbances. Distributed roughness elements are locally placed near the leading edge with a span-wise wavenumber, to ex- cite the corresponding crossflow vortices. The response of boundary layer to external disturbances such as roughness heights, span-wise wavenumbers, Rey- nolds numbers and freestream turbulence characteristics are studied. It must be noted that the experiments were conducted at a very low level of freestream turbulence intensity (T u). In this study, we fully reproduce the freestream isotropic homogenous turbulence through a DNS code using detailed freestream spectrum data provided by the experiment. The generated freestream fields are then applied as the inflow boundary condition for direct numerical simulation of the wing. The geometrical set up is the same as the experiment along with application of distributed roughness elements near the leading edge to precipi- tate stationary crossflow disturbances. The effects of the generated freestream turbulence are then studied on the initial amplitudes and growth of the bound- ary layer perturbations. It appears that the freestream turbulence damps out the dominant stationary crossflow vortices.
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 13 p.
Swept-wing boundary layer, surface roughness, receptivity, freestream turbulence, crossflow instability
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-123192OAI: oai:DiVA.org:kth-123192DiVA: diva2:625311
QC 201306042013-06-042013-06-042013-06-04Bibliographically approved