Aerodynamics Laboratory

Aerodynamics Laboratory
Department of
Aerospace and Mechanical Engineering
at
The University of Arizona

Lab Homepage

The Aerodynamics Lab is located in the department of Aerospace and Mechanical Engineering at The University of Arizona. The lab is focused on the study of flow separation and active flow control. It is directed by Professor Israel J. Wygnanski; he is also a member of the Faculty of Engineering, Tel Aviv University.

This lab contains wind tunnels and 1 water tunnel.

2' x 3' Closed Circuit, Temperature Controlled, Wind Tunnel
2' x 3.5' Open Circuit, Wind Tunnel
3' x 2' Open Circuit, Wind Tunnel
18" x 18" Oscillatory Flow Vertical Water Tunnel

We also have an area for 3-D model testing and a Anechoic Chamber. Measuring devices include: PSI Model 8400 Pressure TransducerScanivalve Zoc Pressure Transducer pressure transducers, Laser Doppler Velocimetry, and Particle Image Velocimetry.

Approximately 20 faculty, staff and students conduct research on the dynamics of flow and Active Flow Control (AFC), including oscillatory blowing that can delay separation and enhance lift.

Multimedia Presentations

I. Separation Control

The introduction of periodic oscillations into a turbulent boundary layer enables it to resist larger adverse pressure gradients without separating. It therefore increases the lift and reduces the parasitic drag that is generated by wings at angles of incidence and flap deflections at which the flow would otherwise be separated. The method is very robust and its effectiveness is not hindered by triggering early transition, thickening the turbulent boundary layer, or changing the Reynolds number and Mach Number. The method has little in common with stationary boundary layer control schemes like vortex generators, steady blowing or suction although its efficacy is judged by comparison with the more traditional schemes.

The complexity of the flow requires extensive experimental investigation to be accompanied by numerical simulationand theoretical modeling(whenever possible) in order to determine the leading parameters governing this phenomenon.

A series of circulation and separation control experiments using different control strategies encompassing steady or periodic blowing or suction as well as zero net mass flux periodic excitation were initiated. The impact of these control schemes is initially investigated on two-dimensional airfoils in an attempt to better understand the effects of each technique rather than produce superior airfoil performance. Special attention is paid to the effects of actuation location, slot sizes, surface curvature, and the shape of the trailing edge on all modes of separation control. An investigation of the transient processestaking place during flow separation or reattachment to a solid surface was undertaken because it represents the first step in a rational development of closed loop control strategies.

The instantaneous details of the flow should be investigated with non-intrusive instrumentation such as Particle Image Velocimetry or Laser Doppler anemometry. From the practical point of view a full scale convincing flight demonstration is required to prove the efficacy of the approach that takes advantage of instabilities and uses unsteady flow to overcome steady flow performance limitations. We need to explore further the effects of compressibility, sweep-back and finite wing planforms. We should also attempt to control dynamic stall for helicopter rotor applications. One may also use this form of flow control to design very thick wings as well as highly cambered compressor and turbine blades and finally flow control may replace cumbersome and complex control surfaces.

II. Mixing, Flow Resonances and Chemical Reaction

The size and shape of combustion chambers, afterburners and nozzles are determined to a large extend by rate of mixing achieved. Mixing rates can be enhanced by periodic forcing and by geometrical design. Harmonic perturbations introduced at the initiation of the mixing process are able to enhance the rate of the process by a factor of 2 to 3. A combination of forcing frequencies can do even better. By using non-linear interactions one may control the shape of jets (i.e. they may appear as if generated by exotic non-circular nozzles) and to some extent alter their direction. In this way the interference between jets and empenage can be affected. Since turbulent mixing affects the rate of chemical reaction, active control of the process improves the efficiency of combustion, changes IR signatures, alters and redirects noise as well as stabilizes flames. Noise radiation is also affected by mixing and in some instances (e.g. cavity flows) it is totally governed by it. Thus active control of the mixing process has probably more applications than the active control of separation though the two are linked particularly when reattachment is concerned.

The aerolab research program is concerned with all these programs and builts inroads into better fundamental understanding of the flows involved while at the same time demonstrating the applicability of active and passive flow control.

Contact Information

Telephone: 520-626-3802
Postal address: 1130 N. Mountain , Tucson, AZ 85721