On the Role of Secondary Structures During Leading Edge Vortex Lift Off and Detachment on a Pitching and Plunging Flat Plate

Abstract

The present study is a prelude to applying different flow control devices on pitching and plunging airfoils with the intention of controlling the growth of the leading edge vortex (LEV); hence, the lift under unsteady stall conditions. As a pre-requisite, the parameters influencing the development of the LEV topology must be fully understood, and this constitutes the main motivation of the present experimental investigation. The aims of this study are twofold.First, an approach is introduced to validate the comparability between flow fields and LEV characteristics of two different facilities using water and air as working media by making use of a common baseline case. The motivation behind this comparison is that with two facilities the overall parameter range can be greatly expanded. This comparison includes an overview of the respective parameter ranges, control of the airfoil kinematics and careful scrutiny of how post-processing procedures of velocity data from time-resolved particle image velocimetry (PIV) influence the integral properties and topological features used to characterise the LEV development.Second, and based on results coming from both facilities, the appearance of secondary structures and

Insights into leading edge vortex formation and detachment on a pitching and plunging flat plate

“…In continuation of earlier efforts by Kissing et al (2020), the occurrence of secondary structures is quantified with the approach introduced by Huang and Green (2015). This method identifies Lagrangian Coherent Structure (LCS) saddle points in the flow field by intersections of repelling and attracting ridges.…”