Swept-wing boundary-layer receptivity to localised surface roughness
2011 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645Article in journal (Other academic) Submitted
The receptivity to localised surface roughness of a swept-wing boundary layer is studied by direct numerical simulation (DNS) and computations using the parabolised stability equations (PSE). The DNS is laid out to reproduce wind tunnel experiments performed by Saric & coworkers, where micron-sized cylinders were used to trigger steady crossflow modes. The amplitudes of the roughness-induced fundamental crossflow wave and its superharmonics obtained from nonlinear PSE solutions agree excellently with the DNS results. A receptivity model using the direct and adjoint PSE is shown to provide reliable predictions of the receptivity to roughness cylinders of different heights and chordwise locations. Being robust and computationally efficient, the model is well suited as a predictive tool of receptivity in flows of practical interest. The crossflow mode amplitudes obtained based on both DNS and PSE are 40% of those measured in the experiments.Additional comparisons between experimental and PSE data for various disturbance wavelengths reveal that the measured disturbance amplitudes are consistently larger than those predicted by the PSE-based receptivity model by a nearly constant factor. Supplementary DNS and PSE computations suggest that possible natural leading-edge roughness and free-stream turbulence in the experiments are unlikely to account for this discrepancy. It is more likely that experimental uncertainties in the streamwise location of the roughness array and cylinder height are responsible for the additional receptivity observed in the experiments.
Place, publisher, year, edition, pages
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-48464OAI: oai:DiVA.org:kth-48464DiVA: diva2:457678
QS 2011 QS 201203162011-11-182011-11-182012-03-16Bibliographically approved