A Novel Method to Induce Hydrodynamic Instability in Boundary Layer Flows

We have developed a method to induce passive hydrodynamic displacement of boundary layer type flows by implementing spatially patterned hydrophobic patches in the form of bands and spots on the surface of a boundary layer plate. These patterns can be designed as parallel bands of a certain width, spacing and direction, or spots with a random or regular distribution of a certain shape, size and spatial density. We will present results from a series of experiments where the response of boundary layers in low to medium Reynolds number ranges to these spatial forcing will be demonstrated. Also, we will discuss~potential use of this novel~technique for drag reduction and separation delay applications where our technique could be used to replace riblets, trip wires and vortex generators.