Effect of gravity on contact angle

The Thermodynamic Characterization of Wetting by Submitting a Sessile Drop to Microgravity

“…These observations were supported by the theoretical calculations of Fujii and Nakae [20]. According to Leger, Joanny, Fujji and Nakae, only forces that become increasingly large at the contact line such as the viscous force on an advancing liquid can affect Young's law.…”

“…Equation 20 represents the ideal wetting in the absence of gravity. In a real process without gravity, part of the available surface energy will be lost in the form of entropy during wetting and A k will be slightly smaller than A o .…”

Local thermodynamic derivation of Young's equation

“…In fact, this nonlocal approach has been applied to special, elementary cases (such as drops in contact with solid surfaces in the absence of gravity and thin capillaries [4] or the meniscus formed on a vertical solid wall [5]) where the total energy can be calculated analytically. In more general cases, where analytical solutions do not exist (e.g., drops under gravity [6] or menisci inside thick capillaries [7]), variational methods are used or, alternatively, the energy is calculated numerically [6,8]. The conclusion is always the same: minimization of the total energy in any particular case leads to Young's equation.…”

The Thermodynamic Characterization of Wetting by Submitting a Sessile Drop to Microgravity

“…Equation 20 represents the ideal wetting in the absence of gravity. In a real process without gravity, part of the available surface energy will be lost in the form of entropy during wetting and Ak will be slightly smaller than Ao.…”