INFLUENCE OF SURFACE IMPERFECTIONS WITH SLIGHTLY ROUNDED CORNERS ON THE EXPECTED LAMINAR-TURBULENCE TRANSITION LOCATION

Abstract

The presence of surface imperfections on aerodynamics devices, such as steps or gaps of height/depth h comparable with the local boundary-layer displacement thickness δ∗, might alter the spatial development of linear mechanisms that trigger the laminar-turbulent transition process, such as Tollmien-Schlichting (TS) waves or Crossflow Instabilities (CFI). Traditionally, the numerical studies for such configurations assumed that the geometry of the surface imperfections is rectangular at the corners. However, an initial work by Zahn and Rist [1] showed the tremendous impact on the computed N -factor envelope curves if the edge of the corner is slightly distorted. Despite this, no parametric studies have been conducted in order to better quantify the impact of such modelling of the step geometry.