Learning from dolphin skin - Drag reduction by active delay of transition: Flow control by distributed wall actuation

Abstract

Control strategies for laminar flow control above a surface are investigated. A flexible membrane displaced by multiple piezo-polymer composite elements is used as actuator in wind-tunnel experiments. Direct methods of damping Tollmien-Schlichting waves are compared to a biomimetic approach imitating the dampingmechanisms of a compliant skin. In both cases, model predictive control algorithms are applied to control the multi-bar actuator segments. For the biomimetic approach, reduced models of compliant surfaces are developed and parametrized by direct optimization and according to numerically generated optimal wall properties. Damping results of up to 85% RMS value are achieved. © 2012 Springer Berlin Heidelberg.