# What is Contact angle: Definition and 18 Discussions

The contact angle is the angle, conventionally measured through the liquid, where a liquid–vapor interface meets a solid surface. It quantifies the wettability of a solid surface by a liquid via the Young equation. A given system of solid, liquid, and vapor at a given temperature and pressure has a unique equilibrium contact angle. However, in practice a dynamic phenomenon of contact angle hysteresis is often observed, ranging from the advancing (maximal) contact angle to the receding (minimal) contact angle. The equilibrium contact is within those values, and can be calculated from them. The equilibrium contact angle reflects the relative strength of the liquid, solid, and vapour molecular interaction.
The contact angle depends upon the medium above the free surface of the liquid, and the nature of the liquid and solid in contact. It is independent of the inclination of solid to the liquid surface. It changes with surface tension and hence with the temperature and purity of the liquid.

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1. M

### Is a Static Contact Angle Model Appropriate for Microgravity Fluid Simulations?

Hi PF! I have an experiment where a wedge about 160mm long is in microgravity. I withdraw silicone oil from the wedge at a relatively slow rate (no turbulence). Since the wedge angle is small, a lubrication approximation is made. Inertia is shown to be low. I want to simulate this flow. When...
2. M

### Fluids: Kistler contact angle model

Hi PF! I keep seeing Kistler's contact angle model wrote like this $$\theta_d = f(Ca+f^{-1}(\theta_e)) : f = \arccos\left( 1-2\tanh\left( 5.15 \left( \frac{x}{1+1.31x^{0.99}} \right)^{0.706} \right) \right)$$, where the plot then has a sort of break, something like this: But this is not the...
3. E

### Surface tension and Young's contact angle

I came across this diagram, the ##\gamma##'s are supposedly forces per unit length of the respective interfaces: It's not clear what these forces are acting on. ##\gamma_{SL}## and ##\gamma_{LG}## look like they could be acting on a small bit of water right at the end, but I have no idea what...
4. M

### I Parameterize a circle based on the contact angle with a wedge

Hi PF! Given a 2D plane, the following is a parameterization of a circular arc with contact angle ##\alpha## to the x-axis: $$\left\langle \frac{\sin s}{\sin\alpha},\frac{\cos s - \cos\alpha}{\sin\alpha} \right\rangle : s \in [-\alpha,\alpha]$$ However, I am trying to parameterize a circle...
5. ### Dynamic contact angle simulation in COMSOL

I am doing the dynamic process of a water droplet impinging onto a wax substrate in COMSOL, using the Phase Field method for tracking the free surface. I am able to do the simulation for Static Contact Angle(SCA) i.e i am imposing a fixed contact angle throughout the time step in wetted wall...
6. ### I Measuring advancing contact angle

Hi everyone ! I'm currently working on a project for which I need to measure the advancing contact angle of a liquid on a solid, specifically the advancing contact angle of a molten thermoplastic on carbon fibers. My understanding is that there is a difference between dynamic contact angles...
7. ### Measuring contact angle of immiscible liquids

I am looking for sources which describe how to measure the contact angle between immiscible liquids in a tube. The literature seems to be extremely lacking so if anyone has any knowledge I would appreciate the help.
8. ### A Contact Angle of Immiscible Liquids in a Tube

I'm having trouble finding any sources which describe how to accurately measure the contact angle between immiscible liquids in a tube. Any help would be appreciated.
9. ### I Why does high surface energy of the solid have more wetting?

Hello. Recently, I have read the article about plasma surface treatment. The article says contact of the plasma to the surface of the sample increases surface energy by transferring plasma energy to the surface. Then it is suddenly saying that wettability of some industrial ink or paints on...
10. ### Why is air-water contact angle usually assumed to be 0 ?

I am a Ph.D student currently interested in fluid flow in porous media (rocks in my case). I am currently trying to find the range of values for the contact angle in air-water-sandstone systems at shallow reservoir conditions (say 7.5MPa and 35 degrees C). The only value I have managed to come...
11. ### Modeling Hydrophobic Interactions

Hi, I am trying to design or find a simulator for hydrophobic/hydrophilic interactions which can be used in tandem with a multi-objective optimization framework such as Jmetal or etc... I am having trouble determining a generalized approach for modeling the contact angle from younge's equation...
12. ### Surface Friction and Energy Modeling

Hi, I am a student interested in wetting and super-hydrophobic surfaces. I am very new to this field and am a software engineer, and as such do not have strong mechanical or chemical background. I am trying to model contact angle and surface energy for super-hydrophobic surfaces. However my...
13. ### Contact angle and anti reflective coating.

Hi all, just want to ask is there any correlation between the contact angle of a anti reflective coating? i.e the bigger the angle, the better the anti reflective coating? Thanks in advance.
14. ### Contact angle of liquid drop on solid surface.2

Can anyone explain point 44 of the attached pdf document on surface tension. (Here's the link in case attachment doesn't work: http://www.sakshieducation.com/EAMCET/QR/Physics/Jr%20Phy/12Surface%20tension%20_198-208_.pdf How is the surface tension direction found out? {i know it...
15. ### Contact angle of liquid drop on solid surface.

Can anyone explain point 44 of the attached pdf document on surface tension. (Here's the link in case attachment doesn't work: http://www.sakshieducation.com/EAMCET/QR/Physics/Jr%20Phy/12Surface%20tension%20_198-208_.pdf) How is the surface tension direction found out? Also why is...
16. ### HELP Calculating contact angle of benzene.

Homework Statement In an experiment to determine how well benzene wets glass, benzene was found to rise to 1.71 mm in a certain capillary tube at 20.0 C. In the same tube, water rose 4.90 mm at 20.0 C. Calculate the contact angle for benzene, give that at 20.0 C, benzene = 0.879 gcm^-3...
17. ### Temperature dependence of contact angle in liquids

How does contact angle change with temperature and why? Does capillary rise have a temperature dependence?
18. ### Liquid drop contact angle: THF, mica & graphite

This is a long shot, but maybe someone will know or can point me in the right direction. I'm looking for an experimental value for the contact angle between tetrahydrofuran (THF) with both mica and graphite substrates. I've done numerous googling and also did a search on the web of knowledge...