An approach to developing active control strategies for separated flows is presented. The methodology proposed is applied to the incompressible unsteady wake flow behind a circular cylinder at a Reynold's number of 100. Control action is achieved via cylinder rotation. Low‐order models which are amenable to control and which incorporate the full non‐linear dynamics are developed by applying the proper orthogonal decomposition technique to data provided by numerical simulation. This process involves extensions to the usual POD approach and the results are therefore assessed for two ‘open‐loop’ test cases. The predictions are found to be satisfactory for control purposes, assuming the model can be reset periodically. The use of these models for optimal control is discussed in a companion paper, Part II. Copyright © 1999 John Wiley & Sons, Ltd.

No abstract

SUMMARYIn Part I, an approach to deriving low-order models suitable for use in the development of active control strategies for separated ows was presented. The methodology proposed was applied to a numerical simulation of the incompressible, unsteady wake ow behind a circular cylinder at Re = 100, with control action achieved via cylinder rotation. The resulting low-order models were found to predict the ows in four open-loop test cases with su cient ÿdelity to justify their application in model-based control of the vortex-shedding ow. In Part II, optimal control theory is used to implement the model-based control, and data from numerical simulations of the controlled ow are presented. It is found that the level of wake unsteadiness can be reduced, even when the low-order model is reset on the basis of limited ow ÿeld information. The degree of reduction is dependent on the accuracy of the low-order model, and ways of reÿning it in the light of control simulations are considered. However, results from two straightforward approaches to this problem suggest that it is easy to 'over-tune' the model, resulting in less successful control.

No abstract

No abstract