Control of tollmien-schlichting waves on a natural laminar airfoil via dynamic surface modulation
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Authors
Wylie, John, David Berry
Issue Date
2023-05
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Aeronautical engineering
Alternative Title
Abstract
The study presented here demonstrates experimental mitigation of Tollmien-Schlichting (TS)waves on Natural Laminar Flow (NLF) wind tunnel models. Experiments were first conducted
on an unswept NLF airfoil at a chord-based Reynolds number of 9:90 x 10^5 and then
on a 30 degree swept-back NLF airfoil at a chord-based Reynolds number of 8:45 x 10^5. Control
of TS waves was facilitated by dynamic surface modifications using piezoelectrically-driven
oscillating surface (PDOS) actuators. On each model, the actuators were located at three
streamwise locations on the airfoil suction side. For TS wave control, a disturbance was
introduced to the flow using the upstream actuator, which phase-locked the TS waves. The
downstream actuators were used to mitigate the induced TS waves by introducing anti-phase
disturbances with the proper amplitude. The disturbances included either single frequency
or multi-frequency input waveforms. The TS waves were mitigated in both open- and closedloop
control schemes for the unswept model, and in open-loop for the swept-back model. In
open-loop control, the results demonstrate that dynamic surface modification can be used
to mitigate the TS waves for varying frequency bandwidths even in the presence of a large
adverse pressure gradient. In addition, a closed-loop scheme, using an iterative learning
control algorithm, succeeded in reducing the induced disturbance amplitudes to 11% of their
original values. The experiments demonstrated the ability not only to mitigate the waves
but also to amplify them if transition to turbulence is desired. With actuators implemented
on the swept-back configuration, experiments indicated that this flow control method feasibly
suppressed the Tollmien-Schlichting waves in a similar fashion. In addition, for the
unswept model without actuation, a separation bubble was identified near the third PDOS
actuator. Preliminary results showed that using the upstream PDOS yielded mitigation of
the separation bubble.
Description
May2023
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY