Base Flow Modification by Plasma Actuation for Swept Wing Transition Control

Base Flow Modification by Plasma Actuation for Swept Wing Transition Control

Peng, K. (TU Delft Aerodynamics)

Kotsonis, M. (promotor)
Avallone, F. (promotor)

Delft University of Technology

2024-06-03

In the upcoming decades, a substantial growth in the commercial aviation market is anticipated, accompanied by an increasing societal awareness of global warming. This circumstance necessitates a technological development for emission reduction in future transport aircraft. A method for aerodynamic efficiency improvement is the so-called Laminar Flow Control (LFC), which can potentially achieve a considerable boost in aircraft efficiency. The research described in this thesis focuses on the specialised strategy of Base Flow Modification (BFM) based on plasma actuators (PAs), a promising member in the LFC family. The results of this booklet is divided into three main parts. The first part explores the effects of unsteady PA-induced perturbations on a swept wing boundary layer dominated by stationary crossflow (CF) vortices, representative of typical cruise flight regimes. Key parameters such as forcing frequency and streamwise location of PAs are scrutinized, which have pronounced effects on the development of crossflow instabilities (CFIs). To focus on the PA-induced unsteady disturbances, PAs are operated at very low power to minimize the net BFM effect. The second part primarily aims to experimentally validate the reduction of CF component achieved by the plasma-based BFM. It also delves into the effects of the PA forcing on the base flow and developing CFIs in a swept wing boundary layer. Employing the BFM strategy, a simplified predictive model is constructed with linear stability theory analysis to infer CFI modes’ characteristics. The achieved CF reduction and the base flow direction are traced under various momentum coefficients, which are controlled by the applied high voltage amplitude. Moreover, the streamwise growth of stationary and travelling CFIs is investigated under the condition of PA actuation. The last part focuses on controlling CFIs and laminar-turbulent transition in an experimental swept wing model using the plasma-based BFM technique. A simplified model coupled with linear stability theory analysis predicts the net BFM effect on CFI modes. Experiments are conducted in a low-turbulence wind tunnel where PA is operated at constant input voltage and frequency to achieve the BFM control. Various parameters of the PA-based BFM technique are investigated, namely the Reynolds number, angle of attack and wavelength of dominated stationary CFI modes. The results generally confirm the stabilising ability of BFM on the swept wing boundary layer. More importantly, the PA-based BFM essentially renders the boundary layer more susceptible to travelling CFIs. In the presence of net BFM effect and intrinsic PA unsteadiness, the PA-based BFM technique achieves transition delay with specific combinations of Reynolds number, angle of attack and wavelength of dominated stationary CFI modes.

Plasma
swept wing
boundary layer
crossflow instability
transition
flow control

https://doi.org/10.4233/uuid:6e1e3a01-d5bf-4101-ac23-2fc1720bb9ba

978-94-6366-866-8

Institutional Repository

doctoral thesis

© 2024 K. Peng