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Materials Science at Oregon State University

Exploiting multiphase interactions in fluid mechanics

Date: Thursday, Oct 24th
Presenter: Prof. Travis Walker, OSU Chemical, Biological, and Environmental Engineering


Fundamental Interests: The addition of multiple phases to flow systems drastically increases the complexity of the flow physics. These complexities reveal themselves on both the macroscopic and microscopic length scales and can involve solids as well as immiscible and miscible fluids. Com- plexities such as the presence of polymers, surfactants, colloids, and particulates to flow systems create complex fluids or soft materials that respond in a nonlinear way to stress. The interactions of particles with viscoelastic materials are found readily in nature. From the suspension of shavings in drill mud to the adhesion of particulates in the mucus lining of our lungs, the non-Newtonian rheological properties of the interacting fluid can dominate the physical responses of solid particles. Specifically, the elongational viscosity, dominant in many polymer solutions, can be exploited to pull particles from a surface or adhere particles to a surface or to increase or decrease the drag force on a particle.

Enhanced Particle Removal: The introduction and subsequent removal of highly elastic so- lutions from surfaces has allowed industry to effectively remove particulate contaminants from high-grade silicon. The advantage of this continuous process over conventional techniques is the noninvasive removal of the particulates, while generating limited nonhazardous aqueous waste. Our group investigated the use of polymeric liquids to effectively eliminate particles without damaging the delicate surfaces. To investigate this removal, we studied two different flow types (syphoning and rinsing) of various rheological fluids to understand the governing physics that allow for removal. We present a simple theoretical model showing that the presence of large elongational viscosities are exploited by local flow gradients, creating substantial polymer contributions to the stress field that correlate with the onset of removal of the particulates from the surface.

Travis Walker, PhD is a new assistant professor in the Chemical, Biological, and Environmental Engineering department. His research includes the study of a number of areas associated with transport in complex fluids and multiphase flow phenomena. He completed his PhD and Masters of Science in Chemical Engineering at Stanford University in 2013 and 2010 respectively. In 2008 he graduated from South Dakota School of Mines and Technology with two degrees, one in Chemical Engineering, and the other in Applied and Computational Mathematics.