Abstract
Feedback control of fluid flows presents a challenging problem due to nonlinear dynamics and unknown optimal operating conditions. Extremum seeking control presents a suitable method for many flow control situations but involves its own challenges. In this paper, we provide a brief analysis of the extremum seeking method, with attention to modifications that we find to be advantageous. In particular, we present an adaptation for optimisation of the frequency of a harmonic input signal, a common scenario for open-loop flow control systems. We then present results from the experimental implementation of our modified method to the open-loop control system of Oxlade et al. (J Fluid Mech 770:305–318, 2015), an axisymmetric bluff-body wake, forced by a pulsed jet. We find that the system is able to achieve optimal operating conditions in both the amplitude and frequency of the harmonic input signal, and is able to largely reject the disturbances arising from measurements of a highly turbulent flow. We finally show the ability of the extremum seeking system to adapt to changing conditions.
Highlights
Fluid flows are ubiquitous throughout systems of engineering interest, and the behaviour of such flows is often of critical importance
We show that a modified extremum seeking (ES) controller may be applied to a bluff-body wake to provide real-time optimisation of pulsed jet forcing for drag reduction
We present the successful application of an ES controller to the open-loop control system of Oxlade et al (2015): a highly turbulent bluff-body wake forced by a harmonic pulsed jet, variable in both amplitude and frequency
Summary
Fluid flows are ubiquitous throughout systems of engineering interest, and the behaviour of such flows is often of critical importance. While passive systems generally involve geometric modifications (see for example Park et al 2006), active systems are those that require some energy input via an actuator The nature of this input is either decided a priori for an open-loop system Closed-loop or feedback control is a mature research topic with a wealth of theory and methods available The application of such methods to turbulent fluid flows has been a topic of research within the fluids community for some time (see for example Choi et al 2008; Brunton and Noack 2015, for reviews), but generally has limited success in practice due to the difficulties in finding accurate models for the flow in question. The feedback control of many flows such as bluff-body wakes remains a significant challenge
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
