Drag Control through Wrinkling on Curved Surfaces (Denis Terwagne, Université Libre de Bruxelles)

We introduce a new class of Smart Morphable Surfaces, or ‘Smorphs’, that employs a wrinkling instability on curved surfaces to generate customizable, switchable and tunable topography (see Figure 1). Inspired by the dimpled patterns that these surfaces can exhibit, which are reminiscent of the topography of golf balls, we explore their use towards drag reduction and control, using a single pressure signal. Our surfaces are fabricated using rapid digital fabrication techniques and their mechanical behavior is systematically explored and characterized through precision model experiments. We demonstrate that, using the Smorphs’ mechanism on spheres, a drag reduction of 50% can be achieved over a range of Reynolds number. Moreover, the control of the amplitude of the surface pattern offers the opportunity for drag minimization over a wide range of flow conditions. This dynamic control should find applications in the context of fluidstructure interaction ranging from the automotive industry to aeronautical structures.

Figure 1 : A smorph that employs a wrinkling instability