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In contrast, the equilibrium contact angle described by the Young-Laplace equation is measured from a static state. Static measurements yield values in-between the advancing and receding contact angle depending on deposition parameters (e.g. velocity, angle, and drop size) and drop history (e.g. evaporation from time of deposition).
The Young–Laplace equation is the force up description of capillary pressure, and the most commonly used variation of the capillary pressure equation: [2] [1] = where: is the interfacial tension is the effective radius of the interface is the wetting angle of the liquid on the surface of the capillary
In mathematics and physics, Laplace's equation is a second-order partial differential equation named after Pierre-Simon Laplace, who first studied its properties.This is often written as = or =, where = = is the Laplace operator, [note 1] is the divergence operator (also symbolized "div"), is the gradient operator (also symbolized "grad"), and (,,) is a twice-differentiable real-valued function.
The surfaces of constant μ form oblate spheroids, by the trigonometric identity + + = + = since they are ellipses rotated about the z -axis, which separates their foci. An ellipse in the x - z plane (Figure 2) has a major semiaxis of length a cosh μ along the x -axis, whereas its minor semiaxis has length a sinh μ along the z ...
The contact angle is defined as the angle formed by the intersection of the liquid-solid interface and the liquid–vapour interface. [2] The size of the angle quantifies the wettability of liquid, i.e., the interaction between the liquid and solid surface. A contact angle of = can be considered, perfect wetting.
The opposite process—spreading of a liquid on a substrate—is called wetting. The factor determining the spontaneous spreading and dewetting for a drop of liquid placed on a solid substrate with ambient gas, is the so-called spreading coefficient S: Surface tension diagram of a liquid droplet on a solid substrate.
The Laplace pressure is the pressure difference between the inside and the outside of a curved surface that forms the boundary between two fluid regions. [1] The pressure difference is caused by the surface tension of the interface between liquid and gas, or between two immiscible liquids.
Washburn's equation is also used commonly to determine the contact angle of a liquid to a powder using a force tensiometer. [ 5 ] In the case of porous materials, many issues have been raised both about the physical meaning of the calculated pore radius r {\displaystyle r} [ 6 ] and the real possibility to use this equation for the calculation ...