Flow Control with Ink-jet Printed Polymer Surfaces

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The overarching goal is to design a variety of textured surfaces (both static and time-dependent) fabricated using a variety of polymers, which, in the case of active surfaces, are electroactive. The textured surfaces will take a variety of forms: polymer ink-jet printing can straightforwardly produce a static array of riblets of dimensions designed for maximum drag reduction. The technique may be extended to the printing of Electroactive Polymer (EAP) with electrodes (e.g. graphite) so that the riblets are re-configurable for the flight condition. Therefore 'smart' riblets may be optimised in-flight for maximum drag reduction throughout the flight envelope, or, their configuration adjusted to account for any effects of erosion, so considerably extending their lifetime. In the longer term (i.e. as part of work in subsequent years), the techniques will be developed to drive spanwise travelling waves beneath the turbulent boundary layer. This technique, currently under development in the PI's group, is known to lead to drag reductions roughly three times that possible with static riblets ( 30%) at low Reynolds numbers. It has yet to be verified at high Reynolds numbers. Our proposal of a continuous monolithic EAP surface with embedded electrical actuation and control offers several advantages in terms of ease of manufacture, low maintenance and environmental robustness, all of which are very attractive to the aeronautical sector.