Meniscus Instability of Non-Newtonian Fluid between Parallel Circular Plates : 2nd Repopt; Nonlinear Growth and Viscoelastic Behavior of Air Finger

Abstract

In the present paper, nonlinear growth of disturbance on the meniscus between two circular parallel plates in negative motion and the maximum load required for the separation of liquid were experimentally and theoretically studied. It was found from precise observation for a meniscus that a springing back of the free surface occurs at an early time of movement. A radius of the curvature, ρ, at the tip of the air finger was measured by digitizing a VTR of a meniscus in order to quantify the growth of disturbance. A relationship between ρ/R_Tip and ρh₀/R₀ h·, where R_Tip is a position of the tip of the measured disturbance, h₀ isinitial thickness of the liquid, R₀ the radius of the circular plate and h· the present thickness of liquid, was derived in a simple form. The load required for separating these plates increased with the velocity of plates due to stress overshoot, but decreased or became constant over a higher velocity.