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In physics, the Young–Laplace equation (/ l ə ˈ p l ɑː s /) is an algebraic equation that describes the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of surface tension or wall tension, although use of the latter is only applicable if assuming that the wall is very thin.
This measured pressure permits obtaining the pore diameter, which is calculated by using the Young-Laplace formula P= 4*γ*cos θ*/D in which D is the pore size diameter, P is the pressure measured, γ is the surface tension of the wetting liquid and θ is the contact angle of the wetting liquid with the sample. The surface tension γ is a ...
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 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
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.
For this reason, contact angle is coupled inherently to the curvature term of the Kelvin equation. As the contact angle increases, the radius of curvature will increase as well. This is to say that a system with perfect wetting will exhibit a larger amount of liquid in its pores than a system with non-perfect wetting ( > 0 o).
θ is the contact angle of the liquid on the tube wall; ρ is the mass density (mass per unit volume); r 0 is the tube radius; g is the gravitational acceleration. It is only valid if the tube is cylindrical and has a radius (r 0) smaller than the capillary length (= / ()). In terms of the capillary length, the law can be written as