Abstract
Experimental measurements were performed on a swept flat-plate model with an airfoil leading edge and imposed chordwise pressure gradient to determine the effects of a backward-facing step on transition in a low-speed stationary crossflow-dominated boundary layer. Detailed hot-wire measurements were performed for three step heights ranging from 36 to 49% of the boundary-layer thickness at the step and corresponding to subcritical, nearly critical, and critical cases. In general, the step had a small, localized effect on the growth of the stationary crossflow vortex, whereas the unsteady disturbance amplitudes increased with increasing step height. Intermittent spikes in instantaneous velocity began to appear for the two larger step heights. A physical explanation was provided for the mechanism leading to transition and the sudden movement in the transition front due to the critical steps. The large, localized velocity spikes, which ultimately led to an intermittent breakdown of the boundary layer, were the result of nonlinear interactions of the different types of unsteady instabilities with each other and with the stationary crossflow vortices. Thus, the unsteady disturbances played the most important role in transition, but the stationary crossflow vortices also had a significant role via the modulation and the increased amplitude of the unsteady disturbances.
Recommended Citation
J. L. Eppink et al., "Influence of a Backward-Facing Step on Swept-Wing Boundary-Layer Transition," AIAA Journal, vol. 57, no. 1, pp. 267 - 278, American Institute of Aeronautics and Astronautics, Jan 2019.
The definitive version is available at https://doi.org/10.2514/1.J057437
Department(s)
Mechanical and Aerospace Engineering
Publication Status
Full Access
International Standard Serial Number (ISSN)
0001-1452
Document Type
Article - Conference proceedings
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2024 American Institute of Aeronautics and Astronautics, All rights reserved.
Publication Date
01 Jan 2019
