Small Unmanned Aerial Vehicles
Small unmanned aerial vehicles (SUAV) are robotic aircraft typically weighing only a few kilograms. They are ideal for many applications impossible for larger aircraft, for example low-level aerial surveying. However, our limited understanding of their unique aerodynamics, flight dynamics, and mission capabilities greatly inhibit the exploitation of the full potential of this relatively new class of aircraft. My research addresses many of these challenges and my research group develops methodologies that will advance SUAVs.
Multirotor Aerial Vehicles
A recent research push of my lab is the modelling the aerodynamics of multirotor small aerial vehicles (e.g. quadcopters). The objective is to predict the power needs and trim requirements of these flight vehicles throughout their entire flight range. A particular challenge is their high-speed flight range where, due to the mutual interaction of the flows of the several rotors and subsequent wakes, power needs and control requirements increase drastically. The modelling approaches are computationally efficient and suitable for multidisciplinary design optimizations.
Small Scale Rotors
As part of our multirotor vehicle research, students in my lab are developing various predictions methods of the aerodynamic loads that small scale rotors develop. This loads are important in order to develop sound performance models, but also support the develop robust control laws in the case in autonomous vehicles. The research challenges are related to the small scale flows, often highly skewed wakes and the close proximity of multiple lifting surfaces and wakes. The small scale flows result in highly nonlinear aerodynamics typical for the low Reynolds numbers encountered. Highly skewed wakes, e.g. due to edgewise flight, and multiple lifting systems add to the nonlinearities. The approaches chosen by my team include approaches based on blade element momentum theory, advanced potential flow models, and computational aerodynamics. The theoretical approaches are complemented by wind-tunnel tests.
Wind Tunnel Testing
My research group is located at Ryerson University’s large, low-speed wind tunnel lab (Kerr Hall East 037). We perform various wind-tunnel tests for various purposes, for example, to validate propeller/rotor design codes. The experimental equipment includes:
- A three-degrees of freedom (lift, drag, moment) balance system
- a propeller/rotor test stand that allows tests with inflow conditions at various angles with respect to the propeller/rotor plane (fully axial up to fully aligned with the rotor plane)
- An integrating wake rake that uses an iterative approach to estimate the drag of laminar airfoils. The wake rake is also suitable for being used in flight test.
The wind tunnel and its equipment are continuously updated. For example, recently Ryerson University purchased a new motor that allows for higher speeds (in excess of 220 km/h) and a more consistent flow quality over the entire operating range.
Flight Performance Prediction
My lab is developing computationally efficient methods to predict lift and drag of aircraft. For this purpose, we ahve developed a flight performance code called FreeWake. FreeWake has been used for investigations of micro and small aerial vehicles, as well as of larger aircraft, for example general aviation aircraft and sailplanes. The method’s computational speed and accuracy make it suitable for optimization approaches that includes other design aspects, such as flight dynamics, mission requirements, and structures. One example is the study of winglets for sailplanes and fluid-structure interactions of membrane wings. Future projects include modeling the interaction of a flexible wing with atmospheric wind gusts.
Modelling of Complex Flows
Some of my research is concerned about modelling complex flows, for example of high-lift systems, tilt-rotors, and rotors in hover. All of these problems have the common challenge that the lifting systems (i.e. wings/rotors) intersect or interact closely with wakes. This close interaction can have a profound impact on the lift and drag forces and is also often very difficult to model numerically. Our modelling approaches relies on a potential flow approach (FreeWake) that uses elements with distributed vorticity to represent the lifting surfaces and their subsequent wakes. The use of elements with distributed vorticity results in the avoidance of many of the singularity issues that are commonly encountered with many conventional panel and vortex-lattice codes.
Small Unmanned Aerial Flight in Gusts
Many small and micro aerial flight vehicles operate at low altitude and encounter wind gusts that are often the results of obstacles, such as buildings or trees. This gusty environment poses a challenge, especially due to flightpath upsets, but also an opportunity with the energy present in these gusts. In order to better understand the lower atmosphere gusts, we are currently developing a flight-test UAV. This project has been made possible through the generous support from the Kenneth M. Molson Foundation (http://www.kennethmolsonfoundation.ca/).