Fundamentals and Applications of Active Flow Control

Lecturer: Prof. Avraham Seifert, University Tel Aviv
Date: April 8, 2009 (Wednesday), 14:00
Location: Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague, lecture room A

Prof. Seifert will present two recent research projects conducted in Tel Aviv using active flow control. The first project describes taking airfoil separation control concept to flight while the second describes the application of the newly developed suction and oscillatory blowing actuator for aerodynamic drag reduction of large trucks.

The first part of the talk describes a series of experiments that enabled a flight demonstration of roll-control without moving control surfaces. That goal was achieved using a wing with a part span Glauert type airfoil, characterized by an upper surface boundary layer separation from the two thirds chord location at all incidence angles. The flow over that region was proportionally controlled using zero-mass-flux unsteady Piezo-fluidic actuators. The control was applied to one wing at a time, resulting in gradual suppression of the boundary layer separation, increased lift and reduced drag, leading to a coordinated turning motion of the small electric drone. The extensive collaborative and multidisciplinary study, starting from actuator adaptation, airfoil integration and 2D wind tunnel tests led to the selection of a configuration for the flight demonstrator. Further development of a light-weight wing, Piezo-fluidic actuators along with a compact, light-weight, energy-efficient electronic drive-system was followed by full-scale wind tunnel tests and three successful flight-tests. It was flight-demonstrated that active flow control (AFC) can induce roll moments that are sufficient to control the vehicle flight path during cruise as well as during landing. These were, to the best of our knowledge, first time achievements that should pave the way to further integration of AFC methods in flight vehicles for hinge-less flight attitude and flight path control as well as improved performance and increased reliability with lower observability.

The second part of the talk will describe a recent project, on the verge of commercialization, aimed at fuel savings of large vehicles. Large ground transportation systems such as trucks, trains and busses are a main source of pollution, increase the severity of global warming and are main users of expensive and vanishing fossil fuels. At large allowable speeds the aerodynamic drag is a main source for reduced effectiveness and increased energy consumption of large ground transportation systems.  When part of these vehicles suffers from boundary layer separation (such as the rear region of large trucks), and proper aerodynamic design is not an option (due to functionality considerations) one needs to come up with non-traditional solutions. This talk will describe such a path to reduced drag. The concept is based on a simple and small “add-on” device that should be attached to the rear region of trucks. The device houses the newly developed suction and oscillatory blowing actuator, in order to deflect the boundary layer and delay its separation from the device. The static pressure at the truck “base” is increased this way, reducing the aerodynamic drag. Due to the great efficiency and no-moving parts nature of the actuator, increase of net energy efficiency is achievable.

More information: Václav Uruba

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