Controlling flow in systems
Air flowing over a plane's wing, petroleum flowing in long-distance pipes and the movement of blood in arteries are all governed by the physics behind fluid flow. Recent technological advances in the sensors and software realms have made the exploitation of fluid control systems more advantageous and economically feasible. However, the numerical methods typically applied are highly complicated and non-linear. Simplified approximations are necessary to make the analysis and design of fluid control systems accessible to the majority of researchers. Such was the impetus behind the EU-funded project 'Flow control: Reduced order modelling, nonlinear analysis and control design' (FLOCON). Scientists first sought to create simplified (reduced order) models to form the foundations for analysis and design of flow control systems. The focus was on linear models that are more easily employed but with an eye on expansion to simple non-linear ones as well. Instantaneous velocities at certain time intervals (snapshots) were either collected experimentally via particle image velocimetry or generated theoretically via computational fluid dynamics (CFD) simulations. The team exploited established techniques to produce reduced order models from the data. The models were shown to accurately represent observed flow dynamics. During the second half, the team applied the modelling methodology to the design of a flow control system. The test case was enabling control of the local spinning or rotation of a fluid (vorticity) behind an immersed circular cylinder system. Following an experimental campaign to collect input points over the cylinder and within, researchers estimated a non-linear dynamic model and designed a controller. They tested it numerically in MATLAB and with CFD simulations demonstrating a significant reduction in vorticity with the controller. Control of flow is important to reducing non-linearities and turbulence in many industrial and commercial applications. FLOCON has delivered important tools to help designers develop control systems that work with potential impact on the EU space, transport, energy and security sectors.
