The work in the FCET lab relies heavily on experimental data obtained in our wind tunnel facilities using a number of state of the art flow diagnostic methods, including hot-wire anemometry and laser based measurement tools (e.g. PIV). Computer simulations are also an important part of the work by complementing and enhancing the experimental investigations. An overview of ongoing projects is given below.
1. Feedback Control of Transient Growth in a Laminar Boundary Layer
This project is an ongoing international effort involving researchers from the US and the UK, aimed at addressing fundamental issues pertinent to the delay of boundary layer transition from laminar to turbulent state via model-based feedback control. This work has further implication for the implementation of active control of turbulent boundary layers. For this project, the receptivity characteristics of transient growth instabilities, known to trigger early transition to turbulence, in a Blasius boundary layer are investigated experimentally in our new state of the art low-speed wind tunnel. A schematic of the experimental setup is given in Figure 1.
Figure 1. Schematic of boundary layer plate showing streamwise locations of the roughness elements, plasma actuators and shear-stress sensor.
2. Plasma Actuator Modeling and Design
Single-dielectric-barrier-discharge plasma actuators are being developed for the purpose of flow control. In the context of the transition control problem, the electro-mechanical coupling provided by the plasma actuator is used to negate transient growth due to surface roughness, thus preventing transition (figure 2). Plasma actuators are also to be used for the control of separated shear layers. Presently, there is a significant effort directed at the development of reliable models of these actuators for modeling and control purposes.
Figure 2. Wind tunnel apparatus for the study of transition control via plasma actuation.
3. Separated Shear Layer Investigation and Control
Experimental investigations are presently underway aimed at the development of low-order models for separation control. This project focuses on the separating shear layers from a sharp edge on an axisymmetric model. This specialised model allows for three canonical and closely related separated shear layer flows to be studied: wake, backward-facing step and cavity flows (Figure 3). An important feature of the model is the ability to modulate the thickness of the boundary layer at separation independently of the free-stream velocity (i.e. flow Reynolds number) owing to the presence of two suction strips.
Figure 3. Assembled axisymmetric model with suction strips for the study of seperated shear layers.
4. The Role of Initial Conditions in Turbulence
Turbulence is the last unsolved classical physics problem. Due to the omnipresence of turbulent flows in engineering and real life flows, turbulence is a very important topic of research. The work currently ongoing in FCET group is focus on understanding the role of initial conditions on the development and dynamics of turbulent flows.
5. Landing Gear Noise in an Unsteady Air Stream
In collaboration with Bombardier Aerospace and Aercoustics Engineering Ltd, we are investigating the noise emissions from a landing gear in a highly turbulent airflow in order to improve noise prediction models for these configuration. The tests are undertaken in the newly refurbished anechoic, open-jet tunnel at UTIAS.
6. Low-Reynolds number airfoils for unmanned aerial vehicles
Working with Brican Engineering, a Canadian company based outside Toronto, we have been investigating new laminar airfoil designs for low-Reynolds number applications, such as unmanned aerial vehicles for the civilian market. Particular attention is placed on the laminar separation bubble that can forms on the top surface and trigger transition.
Figure 4. Low-Reynolds number airfoil mounted in the wind tunnel.