University of Minnesota
Aerospace Engineering and Mechanics
Spring 2001 Seminar Series



Control of Turbulence in Fluid Flows: Suppression and Enhancement


Professor Miroslav Krstic

Dept of Mechanical & Aerospace Engineering, University of California, San Diego


Abstract


Due to the dimensionality and nonlinearity of Navier-Stokes equations, fluid flows have received minimal attention in the area of control theory. Fluid flow problems dominate the area of aerospace engineering, but are also present in many applications in mechanical, chemical, nuclear and bioengineering. In many cases the objective is to make the flow more steady (to stabilize it), but in some cases the objective is exactly the opposite - to make the flow more turbulent. We present progress towards solving both problems. We consider the flow in a channel with actuators (for blowing and suction) and sensors (pressure or shear stress) only on the walls of the channel. Using the Lyapunov method, we design feedback controllers that, depending on the gain choice, can either stabilize the flow or make it more turbulent. We prove that the Navier-Stokes equations with our feedback laws as boundary conditions are well posed. What is surprising here is that the control propagates its effect throughout the flow even though it acts only from the walls. This is achieved by exploiting viscosity in the flow, not as a means of dissipativity but as a means of controllability. Computational and visualization results, produced on a supercomputer, show vigorous flows being tamed, and conversely, tame flows being made very agitated by a control effort that is almost negligible relative to the levels of fluctuations in the uncontrolled flow. This is due to a judicious use of measurements and model structure in generating control inputs, i.e., due to the use of feedback.

Friday, March 23, 2001
209 Akerman Hall
2:30-3:30 p.m.


Refreshments served after the seminar in 227 Akerman Hall.
Disability accomodations provided upon request.
Contact Kristal Belisle, Senior Secretary, 625-8000.