Active Control of 2-D Instability Waves on an Axisymmetric Body.
Professional paper for period ending Aug 87,
NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
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Experimental studies have demonstrated the feasibility of Tollmien-Schlichting T-S disturbance cancellation in flat plate boundary layers using a variety of active sources. What is detailed herein is the first experimental study of the generation and cancellation of laminar-instability T-S waves by adaptive heat addition to a laminar boundary layer of an axisymmetric body. Tests were performed in a water tunnel environment on a 91 fineness ratio ellipsoid utilizing strip heaters to create and actively attenuate laminar instability waves. The attenuation signal was synthesized by a modified adaptive filter. The filter was able to actively adapt the attenuation signal to changes in amplitude and frequency of the instability wave with no loss in attenuation downstream. Two important distinctives between Liepmanns work and the current study are the method of signal processing used and the introduction of three dimensionality in the flow. In our work the application of digital filtering techniques to the synthesis of the cancellation signal is unique. Further the flow geometry, although not a fully three dimensional, has elements of three dimensionality that further complicate the utilization of selective heat addition. The current experimental program has established that active heat addition controlled by a digital adaptive filter can successfully attenuate T-S waves in an axisymmetric geometry.
- Test Facilities, Equipment and Methods
- Fluid Mechanics