Seminar"Complex viscoplastic flows in superhydrophobic channels"Hossein Rahmani


Wednesday, August 30, 2023 - 10:00




Micro/Bio/Nanofluidics (Shen) Unit would like to invite you to the seminar by Mr. Hossein Rahmani on August 30 (Wednesday).
Date:   August 30, 2023
Time:  10:00-11:00
Venue: C209, OIST


Hossein Rahmani
Chemical Engineerin, the Laboratory of Complex Fluids Research (LCFR), the Université Laval, Canada


Complex viscoplastic flows in superhydrophobic channels


We investigate the transport of viscoplastic fluids in channels with grooved superhydrophobic walls using a comprehensive modeling approach and numerical simulations. Our goal is to understand the interactions between the fluid rheology and the wall superhydrophobicity, and identify factors that influence the corresponding flow dynamics. Groove orientation, defined by angle theta, can be longitudinal (theta = 0), transverse (theta = 90), or oblique (0 < theta < 90) with respect to the applied pressure gradient direction. A range of channel thicknesses, characterized by the ratio of groove period to half channel height (L/H), and flow parameters, including Bingham number (B), slip number (b), groove periodicity length (ell), slip area fraction (phi), and groove orientation angle (theta), are considered. Perturbation theory along with dual trigonometric series solutions are utilized to derive semi-analytical and explicit-form solutions for the velocity field in thick channel limit, while numerical simulations are employed for both thick and thin channels using the Papanastasiou regularization method. These solutions are developed for all groove orientations, with the oblique case being unique due to the nonlinear effects of the viscoplastic rheology; a feature absent in corresponding Newtonian flows. We obtain explicit-form relations for the flow variables, e.g. average slip velocity and effective slip length tensor, highlighting the strong nonlinear effect of viscoplastic rheology. Linear stability analysis of the homogeneous slip condition for a particular flow configuration (phi = 1) has been also developed, revealing the stabilizing/destabilizing effects of the streamwise/spanwise slip condition on the Poiseuille-Bingham flow.


Hossein Rahmani is a Ph.D. candidate in Chemical Engineering at the Laboratory of Complex Fluids Research (LCFR) at the Université Laval. He completed his master’s studies in Mechanical Engineering at Amirkabir University of Technology (Tehran Polytechnic) with a focus on turbulent mixing layer flows. He joined LCFR in September 2018 and since then has been involved in various research projects. He is interested in Fluid Dynamics phenomena with a focus on non-Newtonian viscoplastic flows, interfacial phenomena, and flows over superhydrophobic and textured boundaries. He is passionate about developing mathematical and numerical models to address complex flow systems. As his Ph.D. project, he studied the complex flows of viscoplastic materials over superhydrophobic surfaces by developing mathematical models and numerical simulations. He has published/submitted seven original research papers in JFM, JNNFM, PoF and ACS to address the complex dynamics of Bingham flows in channels with hydrophobic and superhydrophobic surfaces. 


Prof. Amy Shen


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