Executive Summary : | Recent advancements in micro-fabrication technologies and lab-on-a-chip devices have sparked interest in thermally-driven capillary actuation of drops and bubbles. However, the influence of non-Newtonian rheology on thermocapillary-driven flows remains a mystery. Many biological fluids have rheological characteristics similar to non-Newtonian viscoelastic fluids due to their complex microstructure and suspended micromolecules. This requires a comprehensive understanding of the complicated flow physics. The proposed project aims to combine experimental observations with numerical simulations to delineate the different aspects of viscoelastic fluid physics and thermal Marangoni stresses for various flow configurations and operating conditions. The objectives include categorizing parameters for large drop deformation, breakup, and coalescence, studying three-dimensional drop movement, cross-streamline migration, and confinement effects in a Poiseuille flow, shed light on viscoelastic dynamics of droplets in self-rewetting fluids, and investigating the effects of finite inertia and convective transport around droplets for high Marangoni number values. The methodology will range from fabricating experimental setups to developing computer codes using the coupled level set-volume of fluid (CLS-VOF) method. Robust non-linear rheology models such as Finitely Extensible Non-linear Elastic (FENE), Oldroyd-B, and Phan-Thien-Tanner model will be employed to capture both viscoelastic and shear-dependent viscosity effects in different polymeric fluids. Achieving these objectives will help develop fundamental insight into the intricate interaction between viscoelastic fluid physics and thermal Marangoni stresses, finding the optimum operating conditions for efficient manipulation of drops in microfluidic environments. |