Passive Turbulent Boundary Layer Control through 3D-Printed Dolphin Skin

Various mechanisms for drag and flow separation reduction are continually analyzed and developed across multiple fields. This study examines the efficacy of 3D-printed transverse sinusoidal grooves modeled after dolphin skin to mitigate boundary layer separation as a form of passive flow control, energizing the flow near the wall. A water tunnel generates a turbulent boundary layer across the vertical test plate with a tripped boundary layer, and a rotating cylinder induces flow separation by creating an adverse pressure gradient. The dolphin-inspired models are tested in a range of Re values of 105 with a constant amplitude of 0.9 mm and varying groove spacings from 2.5 mm to 10 mm. It is hypothesized that the model with decreased groove spacing will better capture the flow and enhance momentum near the wall, thereby reducing boundary layer detachment. Time-resolved digital particle image velocimetry (TR-DPIV) is employed to document the flow behavior and quantify flow separation, and the resulting boundary layer profiles, backflow coefficients, and Reynolds stresses are visualized from the data.