An experimental study of the effects of surface roughness on the laminar-turbulent transition of a 2D incompressible boundary-layer

摘要

While it is well known that increasing surface roughness tends to shift the transition location of a boundary-layer upstream, no model is currently able to accurately predict this shift as a function of the roughness parameters (mean roughness, skewness, etc.) for a transition driven by Tollmen-Schlichting instabilities. Moreover, the physics involved in this phenomenon is not well understood. Using a flat plate equipped with three exchangeable inserts whose roughness can be adjusted by 3D printing, experimental data are collected for different roughness values, different stream wise locations and different Reynolds numbers. The cases with rough inserts are systematically compared to the smooth reference cases and the Linear Stability Theory is used to estimate AN values as a function of roughness parameters. These data constitute a first step towards a larger database which will make it possible to create a ΔN model for the prediction of this effect. Hypotheses about the physical phenomena involved (changes in amplification and/or receptivity process) are proposed using the collected data.