Transition in a Separation Bubble

Abstract

In the interest of being able to predict separatingreattaching flows, it is necessary to have an accurate model of transition in separation bubbles. An experimental investigation of the process of turbulence development in a separation bubble shows that transition occurs within the separated shear layer. A comparison of simultaneous velocity traces from probes separated in the lateral direction suggests that Kelvin-Helmholtz waves, which originate in the laminar shear layer, do not break down to turbulence simultaneously spanwise when they proceed to agglomerate. The streamwise development of intermittency t beginning of transition T end of transition, turbulent

Studies on a Blade Leading Edge Separation Bubble Affected by Periodic Wakes: Its Transitional Behavior and Boundary Layer Loss Reduction

“…Lou and Hourmouziadis [5] documented transitional behaviors of separation bubbles on a flat plate subjected to main flow fluctuations, where a pressure gradient over the flat plate was imposed using a contoured wall. A similar study was made by Volino and Hultgren [6], focusing on the effect of free-stream turbulence upon the separation bubble.In contrast, fewer studies have been made on the investigation of periodic wakes affecting leading edge separation bubble on a compressor blade, while several studies have been made on steady-state separation bubbles on the blade leading edge [7], [8], [9]. Paxson and Mayle [10] measured wake-affected velocity profiles of the boundary layer on the leading edge of a blunt test model.…”

Numerical study of instabilities in separated–reattached flows

“…It was shown [22] that the roll-up and pairing of the two-dimensional modes has a stabilizing effect on the higher wavenumber spanwise modes and on the overall three-dimensional growth rate when the amplitude of the three-dimensional modes is small, while the absence of pairing (saturation) can enhance the three-dimensional growth rate. A similar vortex pairing phenomenon has been reported in a study on transition in a separation bubble [25]. McAuliffe and Yaras [26] carried out a through experimental study on the nature of transition in a separation bubble and manipulations of the resultant breakdown to turbulence through passive means of control.…”

Transition Models for Turbomachinery Boundary Layer Flows: A Review

“…It was found by Malkiel and Mayle [62] that it describes very well transition in a separated shear layer under a mean steady oncoming free stream. They observed that intermittency is at maximum in the centre of the shear layer, which means on the line of maximum vorticity, and the maximum value follows very well the law (1).…”