Turbulent flows occur in many natural and engineering systems, e.g., erosion at the river bed, pollution spreading in the urban area, high-speed marine vessels moving through water, and so on. The turbulence plays a key role in the production of friction forces on the wall, the generation of noise, and the transportation of mass and heat. In our lab, we perform high-resolution velocity measurements to understand the mechanics of turbulent flows. We also develop novel micro/nano-textured surfaces for turbulent drag reduction.

Turbulent Flows over Super-Hydrophobic Surfaces

Reducing hydrodynamic skin-friction in turbulent flows has a huge impact on energy saving. For example, 30% reduction of friction drag can save $38 billion per year in maritime transportation. By entrapping air bubbles on the solid wall and supporting  nearly shear-free interfaces, the Super-Hydrophobic Surface (SHS) has showed great potentials to reduce turbulent drag. Still, application of SHS in real-world engineering systems, e.g. cargo vessels, is still a challenge. We are using in-house holographic micro-PIV to study the near wall turbulent flows over SHSs. We resolve the velocity fields in the viscous sublayers, and directly measure the wall friction from them.

• Ling H, Srinivasan S, Golovin K, McKinley GH, Tuteja A, Katz J (2016). High-resolution velocity measurement in the inner part of turbulent boundary layers over super-hydrophobic surfaces. J. Fluid Mech. 801, 670-703.