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Fluid Dynamics Seminar

Monday, Apr. 11, 2011, 4:00 PM
Cullimore Hall, Room 611
New Jersey Institute of Technology

Instabilities in spreading nematic droplets and hanging Newtonian film flow

Te-Sheng Lin

Department of Mathematical Sciences, NJIT

Abstract

In this talk I will present two recent projects in thin film flow. For the first part, spreading of nematic liquid crystal (NLC) droplet, I will present recent progress in the modeling direction. This project is motivated by the experimental work of Poulard and Cazabat (Langmuir, 2005). They show a surprising rich variety of behavior on spreading droplets of nematic liquid crystal, including at least two different emerging lengthscales resulting from a contact line instability. We modified a lubrication model for NLC due to Ben Amar and Cummings (Phys. Fluid, 2001) in a simplified two dimensional case, and show that, for the appropriate choice of parameter values, exhibit 2D version of some of the observed behavior. In the second part, fluid flowing down inverted substrates, we consider free surface instabilities of films flowing on inverted substrates within the framework of lubrication approximation. We allow for the presence of fronts and related contact lines and explore the role which they play in instability development. It is found that a contact line, modeled by a commonly used precursor film model, leads to free surface instabilities without any additional natural or excited perturbations. In addition, there exists a single non-dimensional parameter that controls the wavelike properties of the instabilities. This parameter may be interpreted to reflect the combined effect of inclination angle, film thickness and fluid flux.