Suppression of Wind Tunnel Buffeting by Active Flow Control 2004-01-0805
A well-known problem with open-jet wind tunnels are low-frequency pulsations, which affect the flow quality and thus the quality of the measured data. This so-called wind tunnel buffeting is caused by large-scale vortices in the shear layer, which excite acoustic resonant modes of the wind tunnel circuit.
This paper presents a novel approach to control low-frequency pulsations by means of active flow control at the nozzle exit. The final setup consists of oscillated flaps which are actuated by electrodynamic shakers. Single-frequency sinusoidal signals and band-limited random signals were used for excitation. The oscillated flaps prevent the synchronization of vortex shedding with acoustic resonance by generating forced perturbations in the shear layer at a frequency that is different from the acoustic resonance.
The flaps - which were named FKFS-flaps by the authors - were installed at the IVK 1:4 model-scale wind tunnel. Experimental results from an ongoing experimental study are presented showing the reduction of low-frequency pulsations and the influence of the flaps on pressure distribution and force measurements.
The small space requirements of the FKFS-flaps allows retrofit of existing wind tunnels without major modifications to the tunnel. The installation cost is considerably lower than that of other active systems. Very simple open-loop control is used, which is easier to implement and more stable than a closed-loop system.
Müller BBM GmbH, Institute of Internal Combustion Engines and Automotive Engineering, University of Stuttgart (IVK) Research Institute of Automotive Engineering and Vehicle Engines, Stuttgart (FKFS)
SAE 2004 World Congress & Exhibition
Vehicle Aerodynamics 2004-SP-1874, SAE 2004 Transactions Journal of Passenger Cars: Mechanical Systems-V113-6