2
$\begingroup$

Is the contact angle dependent on gravity? I read it is independent of gravity but this seems counter-intuitive. I feel a liquid kept in 0 gravity won't stay in the container itself, so how can it be independent of gravity?

$\endgroup$

1 Answer 1

2
$\begingroup$

There are at least several models to calculate, predict the contact angle and some involve gravity, others do not. One practical method, the Wilhelmy Plate Method , also described here, establishes a static equilibrium between the hydrostatic force in a column against the surface tension force $$sin(\theta)=1-\frac{\rho g h^2}{2 \lambda}$$ where $h$ is the depressed column height, $\theta$ the contact angle, $\rho$ the fluid density and $g$ the local gravity.

So the answer is yes, a model does exist relating gravity to contact angle, however restricted to a specific arrangement of static equilibrium forces involving weight of the fluid.

Note that the Wilhemy formulation does not involve any property of the solid or gas in contact with the fluid. The other methods that predict contact angle without gravity involve energy relationships between the fluid, solid and gas interface. They are just different models, different balancing of equilibrium forces.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.