Prof. Ruoyu Dong

Beihang University, China.
dongry@buaa.edu.cn

Bio

Dr. Ruoyu Dong is a professor and doctoral supervisor in the School of Astronautics at Beihang University. He received his bachelor's and doctoral degrees in Power Engineering and Engineering Thermophysics from the School of Aerospace Engineering at Tsinghua University in 2011 and 2016, respectively. During his PhD studies, he conducted short-term research visits at Nanyang Technological University in Singapore. After obtaining his PhD, he worked as a postdoctoral researcher at the Center for Soft and Living Matter at the Institute for Basic Science in South Korea. He joined the School of Astronautics at Beihang University in 2022 and was appointed as professor. He has received the Wu Zhonghua Outstanding Graduate Student Award from the Chinese Society of Engineering Thermophysics and has been selected for the National Excellent Young Overseas Program. He also serves as a member of the Youth Committee of the Heat Transfer and Mass Transfer Branch of the Chinese Society of Engineering Thermophysics. As first/co-first/corresponding author, he has published in top journals such as Nature, Nature Communications, ACS Nano, International Journal of Heat and Mass Transfer, etc. His research focuses on fundamental scientific problems in heat and mass transfer and fluid flow in soft matter and multiphase fluid systems, as well as their applications in space thermal control and propulsion.

Title

Transport and flow dynamics of complex fluids from the nanoscale

Abstract

Complex fluids composed of polymers, colloidal particles, or other constituents often exhibit intriguing viscoelastic behaviors, which necessitate thorough investigation from a structure-relationship perspective. In this talk, I present two compelling stories that shed light on inferring transport and flow dynamics of complex fluids through the incorporation of embedded nanoparticles. In the first story, we modeled the translational and rotational diffusion of a rod-shaped nanoparticle in linear polymer melts and the three-dimensional cross-sectional effect of the nanorod were added by increasing its diameter and the rotational dynamics around the axial direction was calculated for the first time. Crossing from the unentangled to entangled regime, the nanoparticle is coupled or confined to polymer matrices to various degrees, resulting in distinct quantitative scaling laws of the diffusion coefficients based on its diameter. In the second story, we experimentally investigated the thinning and pinch-off of viscoelastic suspending drops composed of silica nanoparticles dispersed in a polymer solution. Initially, the suspending threads of the suspension thinned down like a homogeneous liquid, with particles mainly affecting the initial Newtonian necking by increasing the fluid viscosity, until a critical thickness was reached, transitioning from Newtonian to viscoelastic states and the thinning accelerated. Near the final pinch-off, in contrast to the exponential decay of pure polymer solutions, the pinch-off dynamics of viscoelastic drops followed a power-law decay. These two stories aim to distinguish the coupling effect of polymers and nanoparticles in determining the fate of complex fluids.