Description and Prediction of Roughness-Induced Transition in Swept-Wing Boundary Layers

By means of the original method of quantitative thermography, an extensive experimental database on the position, length, and other characteristics of laminar–turbulent transition caused by the development of stationary crossflow vortices initiated by different roughness configurations with documented characteristics was obtained. Accompanying numerical base-flow computations were carried out with commercial gas dynamic software coupled with house-made laminar–turbulent transition module. The experimental and numerical data were used to determine threshold [Formula: see text]-factors of transition and turbulence onsets in a range of chord-based Reynolds numbers (flow velocities) and different roughness configurations. The threshold [Formula: see text]-factors are presented as functions of surface roughness height. A comparison with findings of other researches is given.