Active Control of Tollmien-Schlichting Waves on an NLF Airfoil

Project Sponsor: 
http://www.northropgrumman.com
Focus Area: 
Aerodynamics Research
Description: 

A turbulent boundary layer greatly increases the drag on a wing, and therefore aircraft fuel consumption.  By delaying the transition of organized, laminar flow into disorganized, turbulent flow, billions a year can be saved in fuel costs.  One way that this transition can be delayed is by using a vibrating surface element to suppress the Tollmien-Schlichting (TS) waves responsible.

The Natural Laminar Flow (NLF) airfoil series is designed to passively delay the growth of TS waves.  An array of Piezoelectric-Driven Oscillation Surface (PDOS) actuators are mounted on the suction side of the airfoil.  The upstream actuator will excite a TS frequency that will grow and travel downstream.  A second actuator will apply the anit-phase of the TS wave and use the destructive interference to reduce and eliminate the TS wave.  Particle Image Velocimetry (PIV) will be used to quantify the results.  By phase-locking the PIV data, the small velocity flucuations may be visualized.

The long term goal is to achieve closed loop control on natural TS waves on the NLF airfoil.

 

Figure 1: sample TS cancellation PIV from a previous version of the project. Excitation only (left) and with cancellation (right).

 

Figure 2: NLF 0414f model

 

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