Pulsed Blowing Interacting with a Leading-Edge Vortex

Andrei Buzica,Christian Breitsamter

doi:10.3390/aerospace7010004

Abstract

Manipulation of vortex instabilities for aerodynamic performance increase is of great interest in numerous aeronautical applications. With increasing angle of attack, the leading-edge vortex of a semi-slender delta wing becomes unsteady and eventually collapses, endangering the flight stability. Hence, active flow control by pulsed blowing stabilizes the vortex system, enlarging the flight envelope for such wing configurations. The most beneficial outcome is the reattachment of the separated shear layer during post-stall, contributing to a lift increase of more than 50%. In contrast to high power consuming brute-force actuation, manipulating the flow instabilities offers a more efficient alternative for mean flow field control, which has direct repercussions on the aerodynamic characteristics. However, the flow mechanisms involving jet–vortex and vortex–vortex interactions and the disturbance convection through the flow field are little understood. This paper reports on the unsteady flow field above a generic half delta wing model with a 65 ° sweep angle and its response to periodic blowing. Numerical and experimental results are presented and discussed in a synergistic manner.

Highlights

Vortices are three-dimensional coherent flow features that occur very often in nature, as well as in many relevant technological applications
This paper reports on the unsteady flow field above a generic half delta wing model with a 65◦ sweep angle and its response to periodic blowing
Sustaining the leading-edge vortices is desired for aerodynamic performance increase of swept wing configurations

Summary

Introduction

Vortices are three-dimensional coherent flow features that occur very often in nature, as well as in many relevant technological applications. Tangential blowing/suction at the leading-edge of a 75◦ swept delta wing model successfully delayed breakdown at an incidence angle of α = 54◦ (at which the vortex bursts near the apex) [14]. The different actuation type and experimental setup between the present work and [16] show how the flow response is more dependent on the amplitude and frequency (which is universal) than on the jet form and direction Based on both non-intrusive methods, computational fluid mechanics (CFD) and particle image velocimetry (PIV), the results are analyzed and discussed in a synergistic fashion, focusing on the interaction between pulsating blowing jets and the vortical field. The advantages of both methods are exploited: for example, analysis of the regions in PIV planes contaminated by reflections (near-wall region) is conducted more effectively based on numerical results

Delta Wing Model

Experimental Setup

Numerical Setup

Results and Discussion

Vortex Breakdown

Delay of Vortex Breakdown