Wetting Effect on Torricelli’s Law

Abstract

This Letter presents an experimental study on the effect of wetting on the draining of a tank through an orifice set at its bottom. The investigation focuses on flows of liquids in the inertial regime through an orifice the size on the order of magnitude of the capillary length. The results show that although the flows always follow a Torricelli-like behavior, wetting strongly affects the speed of drainage. Surprisingly, this speed goes through a minimum as the outside surface of the tank bottom plate changes from hydrophilic to hydrophobic. The maximum effect in slowing down the flows (up to 20%) is obtained for a static wetting angle θ_{s} of about 60°. Experiments suggest that the effect of wetting on the exit flows, very likely, is related to the meniscus that forms at the hole's outlet. A simple model is proposed that estimates the variation of kinetic energy within the meniscus. This model captures the main features of the experimental observations, particularly the nonmonotonic variation of the speed of drainage as a function of θ_{s} with a minimum for a static wetting angle of about 60°.

Transition from Exponentially Damped to Finite-Time Arrest Liquid Oscillations Induced by Contact Line Hysteresis

“…This has been tentatively ascribed to a source of dissipation localized in the vicinity of the air-liquid-solid triple line. It echoes several other configurations where wetting conditions affect macroscopic flows, like Faraday waves [6], drop fall down inclines [7,8], Torricelli's law [9], or capillary rise [10,11]. However, there is no quantitative prediction relating wetting properties to sloshing damping.…”

Liquid flow and control without solid walls

“…the velocity profile is essentially plug-like. Remarkably, the flow rate of honey through the antitube was 1.5 times faster than when there was no tube, likely due to competition between orifice wetting 22 and the higher hydrostatic pressure due to the greater height of the honey column in the antitube design.…”

Liquid Helix: How Capillary Jets Adhere to Vertical Cylinders

“…Yet, although the teapot effect has received attention from physicists for centuries [1][2][3][4][5][6][7][8][9][10][11][12][13], a simple quantitative description fully capturing the observations is still lacking. From a practical point of view, understanding the teapot effect is of paramount importance not only for designing food containers but also to better control flows through orifices [14], to avoid fouling up the nozzle of inkjet and 3D printers [15], and for polymer extrusion processes where capillary adhesion causes "sharkskin" instabilities [16].…”