Surface tension occurs due to the tendency of liquid molecules to favor their own kind. Surface tension is important in fluid multiphase systems typically at small length and velocity
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What causes insects to cast large shadows from where their feet are?
I recently stumbled upon this interesting image of a wasp, floating on water:
Assuming this isn't photoshopped, I have a couple of questions:
Why do you see its image like that (what's the ...
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2answers
249 views
Stripeless cleaning of windows
Cross post: http://chemistry.stackexchange.com/q/4377/22
Last week I was discussing with a friend how we thought the stripeless cleaning of windows is achieved when using a cleaner like Windex ...
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Are there any liquids with zero surface tension?
Having read the Wikipedia page on superfluids I'm still not sure if stuff like liquid helium at the lambda point actually have surface tension or not. Is superfluidity the same thing? And are there ...
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3answers
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Surface energy as thermodynamic potential
Consider free energy of sharp interface $\Gamma$
$$ \int_\Gamma \sigma\;\mathrm{d}S $$
or also free energy of diffuse interface of characteristic width $\epsilon$ given by Cahn-Hilliard/Allen-Cahn ...
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1answer
780 views
Why does water flow out of an upside-down bottle? (Rayleigh Taylor Instability)
I am currently reading the excellent book An Indispensable Truth: How Fusion Power Can Save the Planet by Francis F. Chen and I came across this explanation.
The Rayleigh–Taylor Instability
...
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1answer
320 views
How to measure a solid-solid surface energy?
Many techniques exist to measure the surface energy between a liquid and a liquid or a liquid and a gas (see e.g. the wiki page).
Methods to measure the surface energy between a solid and a fluid are ...
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332 views
Zigzag flow of water along a vertical glass window
I've observed this behavior many times. When it rains, the rainwater will form vertical channels along a glass window. The flow of water is mostly confined within these vertical channels and the ...
6
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2answers
156 views
Hydrostatic pressure on a teapot spout
The phenomenon where water flows on the outside side of a teapot spout is named "The teapot effect", and occurs due to a difference in pressure between water and the atmosphere. Consider the image of ...
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3answers
192 views
Why does string not wick down?
I regularly drink tea at work and I often reuse the tea bags (yes I know I'm a cheapskate). Yesterday afternoon I used a tea bag once and kept it in the cup in case I wanted another cup before I ...
6
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3answers
2k views
Why does a bullet bounce off water?
It is known that bullets can ricochet off a body of water. Is surface tension responsible for this or is this the same behavior we see when an asteroid ricochets off the atmosphere? I don't think ...
6
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2answers
626 views
Hydrostatic friction: why do water droplets stay at rest on an inclined glass surface?
Tjis is a non-expert question on a (seemingly simple) text-book topic.
The question is about "hydrostatic friction", defined as follows.
Consider a drop of water resting on a flat surface. If the ...
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2answers
347 views
Surface tension of solutions and mixtures
The inspiration for this question is over on cooking.stackexchange, asking more about actual measurements for commonly consumed liquids, but I'm interested more generally as well.
What determines the ...
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1answer
621 views
Collision frequency at surfaces
Collision frequency for particles in gases is well known, and collision theory is used to derive chemical reaction rates in gases, (and particles in liquid solutions as well). Using the mean velocity ...
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1answer
166 views
Distinctive properties of liquids
The molecules are closely arranged in solids, loosely arranged in liquids and are free to move in gases... But, Why are liquids (especially water) exhibiting these distinctive properties such as ...
5
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1answer
245 views
Are coffee's properties different enough from water's to cause increased spillage while walking?
I recently found this article, which describes how...
It just so happens that the human stride has almost exactly the right frequency to drive the natural oscillations of coffee, when the fluid is ...
5
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1answer
130 views
Dropping condition
Imagine opening a water tap in order to have a smooth and cylindrical outflow and then slowly decrease the flow by adjusting the knob. At a certain moment, the side profile of the flow will become ...
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1answer
119 views
Increment of surface tension with increase of temperature
What is the reason for the increase in surface tension of molten copper/cadmium with increase in temperature?
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4answers
484 views
How far can water rise above the edge of a glass?
When you fill a glass with water, water forms a concave meniscus with constant contact angle $\theta$ (typically $\theta=20^\circ$ for tap water):
Once you reach the top of the glass, the water-air ...
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1answer
81 views
Explanation for breaking up of a stream of water into droplets
Water falling from a tap eventually breaks into droplets at a particular distance from the tap. The distance(from the tap) at which it breaks into droplets is observed to be an increasing function of ...
4
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1answer
153 views
Is this formula for the energy of a configuration of 3 fluids physically reasonable?
I have studied for a couple of months now a mathematical model of the energy of a configuration of immiscible fluids situated in a fixed container such that the fluids fill the container. In other ...
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2answers
429 views
Solving the Young-Laplace equation for arbitrary axisymmetric geometry
Say I have a non-ellipsoidal soap bubble and I want to numerically analyse the pressure in the inner lobe of this bubble here:
The Young Laplace equation gives the pressure difference across a ...
4
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2answers
1k views
Properties of liquid and air bubbles
What is/are the properties of a liquid (e.g. viscosity, surface tension) which is conducive to formation of stable bubbles floating in air (not the bubble inside the liquid)? E.g., if soap dissolved ...
3
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1answer
301 views
Change in appearance of liquid drop due to gravity
A liquid drop is spherical in shape due to surface tension. But why does it appear as a vertical line under the free-fall due to gravity? (E.g. During a rain - falling raindrop) Is there a specified ...
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2answers
186 views
At what size will self-gravitation contribute more to stability than surface tension?
The governments of Earth have embarked on an experiment to place a massive ball of water in orbit. (umm... special water that doesn't freeze)
Imagine this to be a fluid with a given density, $\rho$ ...
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1answer
49 views
boundary conditions for liquid with surface tension
so one uses equations of motion to describe liquids (e.g. Navier–Stokes equations). These are equations for $\vec{v}(\vec{r},t)$ with boundary conditions on the surface $S$ of the liquid (e.g. ...
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2answers
203 views
Need help understanding dynamic and static contact angles
I've run into a conceptual road block. I'm coming to you guys because I think my adviser is getting annoyed with me. The concept involves a meniscus being pulled up a cylinder. I understand that ...
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1answer
696 views
Cooking pasta: why does adding a lid lead to overflow?
When cooking pasta, some organic foam usually forms on the surface of the boiling water and the situation can be kept under control by adjusting the heat (and/or adding some oil).
Covering the pot ...
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0answers
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Finding Surface Tension of water at certain Temperature and Pressure
So the question is:
Using the Young-Laplace Equation (if applicable), find the surface tension (dynes/cm) for water at 20
degrees Celsius with 2.5 psi. Round to the nearest tenth.
...
2
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1answer
51 views
English/German translation of Latin scientific texts in general, “Principia Generalia Theoriae Figurae Fluidorum in Statu Aequilibrii” in particular
I am trying to get my hands on an English or German translation of the seminal work by Gauss on fluid shapes in equilibrium: "Principia generalia Theoriae Figurae Fluidorum in statu Aequilibrii ...
2
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1answer
96 views
Satellite droplets in a breaking liquid jet
The famous example of a dripping faucet is an example of a Rayleigh-Plateau instability in which there is a certain jet radius below which perturbations on the surface will grow to break the jet into ...
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2answers
4k views
'Applications' of surface tension [closed]
What are some common applications, uses, exploitations of the properties of surface tension?
Here is what I mean. A water strider can walk on water, that is a consequence of surface tension. ...
2
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1answer
85 views
Beer bottle leftovers pour quickly only after waiting?
Why is it that after pouring a delicious beer from a bottle, I can hold it upside down for several seconds without reward, but if I wait a bit, the remainder presumably settles at the bottom and ...
2
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1answer
408 views
Contact angle formula still holds for liquid liquid interface?
I have seen in http://books.google.fr/books/about/Molecular_theory_of_capillarity.html?id=_ydSF_XUVeEC&redir_esc=y that there is a formula for the contact angle with a solid wall of a liquid-gas ...
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1answer
464 views
How specifically do emulsifiers work?
I'd like to understand better how emulsifiers prevent droplet coalescence. There must be something more they do than just lower the surface tension between the droplet and the ambient substance. I ...
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1answer
97 views
Why do some liquid metals have anomalously-high surface tension/heat of vaporization ratios?
In a didactic article, Victor Weisskopf estimated the size of molecules in a liquid from measurements of their surface tension and heat of vaporization. If atoms are exceedingly small, then only a ...
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1answer
141 views
What is “surface fluid adhesion energy”?
This is related to my previous question. Pardon me for asking so many questions recently. My physics knowledge is not that good, and some answers are hard to find.
In the question in the link, I ...
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2answers
303 views
Does the potential energy of fluid rising on a string change?
Lets say I have a glass of water at rest. Then I go and hang a string above the water (vertically), such as the end of the string is immersed in the water. Over time some of the water is going to ...
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0answers
58 views
Wrinkling paint - soluto/thermocapillarity - is it due to the primer or solvent [closed]
This is really a one-and-a-half part question.
I know that when paint is mixed with a solvent or used with a primer, it sometimes wrinkles. As I understand, a key physical phenomena here is a ...
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4answers
139 views
How can the surface of a liquid exist if there are no attracting molecules above it?
Okay this is probably a stupid question but here goes:
We know that molecules in a liquid are attracted from all the molecules around it so there is no net attraction. Well, then how do the ...
2
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1answer
152 views
Lotus effect dust removal
I have found hundreds of papers describing the contact angle of water droplet sitting on hydrophobic surface and the change between Wenzel Regime and the Cassie-Baxter regime.
Now, as I understand ...
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2answers
633 views
Bubble formation
I know that surface tension plays a key role in the formation of a bubble. I guess a bubble contains air inside it. Now how is it so that a soap bubble contains air both inside it and outside it?
...
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1answer
251 views
Causes of surface tension between two fluids
Suppose that we have two fluids $A$ and $B$ in a container $\Omega$, and we notice that $A,B$ do not mix.
Can you pleas explain to me what is the cause of this property?
What properties of the two ...
1
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1answer
41 views
Stability and lifetime of soap bubbles formed with light gases like helium or hydrogen?
A friend asked me if it would be possible to make soap bubbles out of a gas like hydrogen and if you did, would they float higher, faster. Due to the lower mass of light gases (compared to the air) I ...
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1answer
150 views
Surface Tension of a Liquid - When a liquid body is acclerating
As far as I understand it (which admittedly isn't very far), surface tension forces are made up by the tension-attractive forces of molecules at the liquid-gas/vacuum interface, such as those between ...
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vote
1answer
96 views
Why does tea rises in the pot but water don't?
I was wondering when I boil water in a pot it only shakes too much while boiling. But I could not figure out why tea rises in the pot when we boil it. it is also a liquid but it starts rising up till ...
1
vote
1answer
150 views
Why does water make a liquid film?
Cut a narrow slit in a thin sheet of opaque material. Immerse the sheet in a liquid,
such as water. After removing the sheet from the liquid, you will see a liquid film in
the slit. The question is: ...
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vote
0answers
123 views
What is the maximum tension in N the string can support [closed]
I have a length of string and I want to know the maximum tension the string can support. I tie one end of the string to the ceiling and the other end to a glass of mass 100 g. The glass is ...
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vote
2answers
95 views
Amount of material required for a pressure tank
I read the answer for the question Why is a hot air balloon “stiff”? and thought something sounded ridiculous. My engineering requirement is that the walls be strong enough. Here $T$ will be the ...
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1answer
82 views
Contact angle of liquid drop on surface
How do you explain point 44 of the attached pdf document on surface tension? Here's the link.
How is the direction of surface tension found out?
(I know it tangential but in which direction along ...
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2answers
49 views
Water entering hole at a depth, surface tension
The following is the question that very commonly appears in all HS textbooks.
A hollow sphere with a hole is taken to a depth of 40cm when the water starts entering the hole. if the surface tension of ...
