Microjet-Based Active Flow Control on a Fixed Wing UAV

Phil Kreth,Farrukh Alvi

doi:10.4236/jfcmv.2014.22006

Abstract

A fixed wing, remote controlled, unmanned aerial vehicle (UAV), has been retrofitted with a system of microjet-based actuators to test microjet efficacy for flow control during flight. This allows one to evaluate the flow control system in a more complex and uncontrolled environment relative to the “clean” laboratory flowfield. The system is composed of off-the-shelf components and provides some appreciation of the challenges associated with implementing such an active control scheme in more “practical” configurations. A wing section with actuators was first tested in a low-speed wind tunnel to characterize microjet control efficacy in the laboratory using surface flow visualizations and particle image velocimetry (PIV). The laboratory results show that the microjet actuators are an effective means of controlling separation with fairly low supply pressures and flow rates. Only relatively robust and straightforward diagnostics can be used to determine the flow conditions on the UAV during flight. As such, tufts are installed on the aircraft’s wing to serve as a qualitative way of measuring control efficacy. Results from the flight tests confirm that this flow control system is capable of delaying flow separation in the complex flows occurring during flight.

Highlights

The demand for improved aerodynamic performance of modern-day aircraft has given rise to the need for active flow control devices that are capable of preventing or minimizing adverse effects that allow one to improve efficiency and/or expand the operational envelopes
Boundary layer separation over the suction surface of wings/airfoils leads to aerodynamic stall at moderately high angles of attack (AOA), which could potentially lead to a loss of control
To further quantify the effect that microjet-based flow control has on the flow around this airfoil, particle image velocimetry was used to obtain velocity field measurements

Summary

Introduction

The demand for improved aerodynamic performance of modern-day aircraft has given rise to the need for active flow control devices that are capable of preventing or minimizing adverse effects that allow one to improve efficiency and/or expand the operational envelopes. These adverse effects can lead to substantial reductions in the. Boundary layer separation over the suction surface of wings/airfoils leads to aerodynamic stall at moderately high angles of attack (AOA), which could potentially lead to a loss of control. Delaying or eliminating flow separation on an aircraft wing is important, especially with the risk of non-recoverable control loss that is associated with stall

Methods

Results

Conclusion