AEROMEMS: Investigation of the viability of MEMS technology for boundary layer control on aircraft

• Research unit: EU RFP
• Project number: 97.0294

Key words (English)

Aerodynamic; fluid mechanics; instability; turbulence; boundary layer; coherent structures; hairpin vortices; flow control; MEMS

Alternative project number (English)

EU project number: BRPR-CT97-0573

Research programs (English)

EU-programme: 4. Frame Research Programme - 2.1 Industrial and materials technologies

Short description (English)

See abstract

Partners and International Organizations (English)

British Aerospace(UK); Dassault Aviation (F); CNRS-
DR18 (F); CNRS-DR6 (F) ; University of Manchester (UK) ; University of Warwick (UK); Techniche Universität Berlin (D) ; Universidad Politécnica de Madrid (E); National Technical University of Athens (EL); Ecole Polytechnique fédérale de Lausanne (CH) ; University of Tel Aviv (IL).

Abstract (English)

The recent developments in Micro Electro Mechanical Systems (MEMS) open new possibilities for the control of turbulent boundary layers. One possible control strategy that could be implemented in a near future is to delay flow separation on aircraft by enhancing the mixing in the lower part of the turbulent boundary layer. Such delay can be achieved by acting locally with small-scale actuators on the near-wall coherent structures of the turbulent boundary layer. These structures are low and high-speed streaks in the srtreamwise direction and streamwise oriented vortices also called 'rolls'. The testing of actuators which act selectively on coherent structures is difficult in real turbulent boundary layers, as the structures are very small and appear randomly in space and time. The evaluation of the effect of a selective actuation on the coherent structures therefore requires to first localize them and then to perform the actuation according to a defined control law. Unfortunately, the present sensing technology does not allow such a real-time detection, but it may become feasible in the near future.
To bypass the detection problem, this study investigates the possibility of artificially generating a highly ordered buffer layer where the spatio-temporal evolution of the streaks is completely known. The highly ordered buffer layer consists in a laminar boundary layer in which low speed streaks are generated by injecting low-momentum fluid at the wall through elongated slots.
The experimental setup developed during this project succeeded in generating coherent structures very similar to the ones revealed in a number of recent numerical studies. To our knowledge, it is the first time that such coherent structures have been artificially generated and captured with experimental techniques. The technique developed in this study can now be used for the development and testing of advanced control techniques, which could be implemented, when MEMS technology will become mature enough for industrial applications.
In parallel a study of MEMS based sensors for skin friction measurements has been conducted in collaboration with Prof. H. Nagib from IIT Chicago to investigate the feasibility of using such sensors for the evaluation of control techniques in turbulent boundary layers. This research is the first one to show that MEMS sensors can be used for accurate measurement of the mean and fluctuating skin friction. These results were presented in November 2000 at the APS Conference in Washington and have been submitted recently for publication to a journal.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0294