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Drying of complex fluids near the contact line : experimental and numerical studies

Abstract : We study the pattern formation induced by drying colloidal suspensions and polymer solutions in a vertical Hele-Shaw cell immersed in a reservoir (dip-coating like set-up). The contact line speed is controlled by pumping the solution from the reservoir. At low capillary number stick-slip motion of the receding contact line is observed for silica suspensions. Periodic strips spontaneously form during drying. We study the wavelength and deposit morphology as a function of the mean receding velocity. The pinning force variation is deduced from the contact line displacement. The effect of the solution pH and size of the particles on the deposit morphology, wavelength, and pinning force is analyzed. Results are compared to some models of the literature. In the same conditions dried polymer films are almost flat, but stick-slip motion is found at higher temperature. In the second part of this manuscript, a 2D model has been developed to describe the flow inside the Hele-Shaw cell induced by the imposed velocity and non-uniform evaporation flux. The model is governed by Stokes equation and Fick's law. A small truncation at the meniscus tip is applied in order to avoid the singularity due to the divergence of the evaporation flux. Lubrication approximation as well as global mass balances are used to express the boundary conditions. Deposit thickness and the flow properties are studied as a function of the process parameters (imposed velocity, evaporation rate, and solute concentration) and the system properties (kinetic viscosity, diffusion coefficient). Finally, we compare our simulation results with a simple model. This model is a first step to study mass transfer in a meniscus
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Submitted on : Thursday, June 6, 2013 - 4:43:47 PM
Last modification on : Thursday, October 27, 2022 - 9:25:42 AM
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  • HAL Id : tel-00831313, version 1

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Ching Hsueh. Drying of complex fluids near the contact line : experimental and numerical studies. Fluid Dynamics [physics.flu-dyn]. Université Pierre et Marie Curie - Paris VI, 2012. English. ⟨NNT : 2012PA066211⟩. ⟨tel-00831313⟩

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