MechE Seminar Series: Hangjian Ling

Speaker: Hangjian Ling

Title: Challenges in using superhydrophobic surfaces for hydrodynamic friction reduction

Abstract: Superhydrophobic surface (SHS) can significantly reduce hydrodynamic friction by supporting a thin layer of gas (or plastron) between the flowing liquid and the solid wall. However, preserving this gas layer in unsteady, complex underwater environments remains challenging. In this talk, I will present our recent work towards understanding and predicting the stability and longevity of SHS. First, I will discuss the plastron stability in turbulent flows, highlighting its degradation with increasing Reynolds number, and the effects of texture geometry on this process. I will introduce a theoretical framework for predicting plastron stability and optimizing surface texture for drag reduction. Second, I will discuss how air diffusion into undersaturated water limits plastron longevity. Our findings show that plastron longevity be depends on environmental conditions, including surfactants, domain size, and temperature, as well as by surface properties, including texture geometry and gas permeability. I will introduce a one-dimensional gas diffusion model that captures the general trends observed in our experiments.

About the Speaker: Hangjian Ling is an Associate Professor of Mechanical Engineering at the University of Massachusetts Dartmouth. He received his Ph.D. from Johns Hopkins University in 2017 and was a Postdoc at Stanford University from 2017 to 2019. His research spans experimental fluid dynamics, turbulent flows, multiphase flows, superhydrophobic surfaces, advanced optical techniques, and collective animal behavior. He has received the NSF CAREER award and the ASME Rising Star award.