The viscosity of a fluid is a measure of its resistance to flow, or be deformed, stirred, and changed shape.
Questions tagged [viscosity]
592 questions
58
votes
3 answers
Why doesn't oil produce sound when poured?
I've noticed that unlike other liquids, when pouring olive oil for example, I don't hear any sound at all from it.
Usually you can hear an audible sound as a cup gets filled with water, as the sound increases in pitch.
What makes the oil behave this…
Moshe
- 731
- 5
- 8
28
votes
7 answers
Frequency difference when water splashes at different temperatures
When I pour hot water (near boiling) and cold water ($5 \unicode{x2103}$) from a height on a platform, there is a distinct difference in the sound that is generated. I feel that hot water splashing has a lower frequency than cold water splashing.…
Black Jack 21
- 736
27
votes
5 answers
What does air "feel" like to a flying mosquito in terms of viscosity?
If I go for a walk at, say 4 km/hour, unless there is a breeze blowing, I probably won't notice the air around me at all. If I go for a swim though, I will immediately notice the viscosity of the water and the effort needed to move through it.
On…
user81619
24
votes
1 answer
Melted chocolate forming fractal branches
Tree-like structure in chocolate
Today I let some melted chocolate solidify in a smooth bowl in my fridge. When it had settled, I gently heated the outside of the bowl with warm water to unstick the chocolate. It caught my attention that the…
Ole Krarup
- 773
- 3
- 9
23
votes
1 answer
Minimum viscosity of liquids
In a lecture by Purcell he mentions that he notices that there aren't any liquids with viscosities much less than that of water, even though they go up seemingly unbounded. In an endnote (endnote 1 in that copy), he mentioned that Weisskopf found a…
genneth
- 8,949
19
votes
4 answers
Explanation that air drag is proportional to speed or square speed?
A falling object with no initial velocity with mass $m$ is influenced by a gravitational force $g$ and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can be written as:
$mg-kv=ma$ (for low speeds)…
EricAm
- 449
18
votes
5 answers
Can vorticity be destroyed?
I have a professor that is fond of saying that vorticity cannot be destroyed. I see how this is true for inviscid flows, but is this also true for viscous flow? The vorticity equation is shown below for reference. From this equation, it looks as if…
OSE
- 1,585
- 1
- 12
- 27
17
votes
2 answers
Height of Water 'Splashing'
Suppose from a height $H$, I throw a ball of mass $M$ and radius $R$ with initial velocity $u$ into a pool of depth $x$ having a liquid with density $\rho$ and coefficient of viscosity $\eta$.
Upto what height will the Water Splash?
This may be a…
NeilRoy
- 293
16
votes
3 answers
How is viscosity described on the molecular level?
What is the 'molecular' origin of the viscosity? The molecular origin of elasticity is almost clear for me: at the very bottom the 'elasticity' comes from the attraction and repulsion between atoms when they are reasonably far from each other or…
deeep
- 173
15
votes
1 answer
In beer, why do bubbles travel faster upwards in the center?
This is a very odd question, but I just so happened to be observing a pint of beer and realized that the bubbles floating up seemed to travel faster towards the center of the glass than towards the edges of the glass.
My first assumption was that…
Corey Mitchell
- 153
15
votes
1 answer
Deriving Stokes' law ($f_v=6\pi\eta Rv$) in a simple way
Is it possible to derive Stokes' law (Viscous force on a spherical body moving in a fluid $f_v=6\pi\eta Rv$) without using the "$\nabla$" operator (at least not in that form) or other theorems/laws other than Newton's law of viscosity and Newton's…
Amsterdam6483
- 1,187
15
votes
1 answer
Ball falling through viscous fluid experiment - strange results
I did an experiment in which I dropped three different sized spherical beads (4mm, 6mm, and 11mm diameter) with the same densities through a viscous liquid (a water-detergent solution). They all fell the same distance, but the biggest one fell a…
米凯乐
- 261
15
votes
2 answers
Why pouring milk from a height makes a chain shape?
I have noticed a chain-like shape when milk is poured from a height into a cup.
The chain pattern repeats itself after some distance till it reaches the milk in the cup.
Any reason behind this?
iappmaker
- 250
14
votes
3 answers
Reason for 6π factor in Stokes' law
According to Stoke's law, the retarding force acting on a body falling in a viscous medium is given by $$F=kηrv$$ where $k=6π$.
As far as I know, the $6π$ factor is determined experimentally. In that case, how is writing exactly $6π$ correct since…
User
- 426
13
votes
7 answers
How does inertia affect an object suspended in a fluid?
When I asked my physics teacher how fully submerged objects are suspended in fluids, she told me it was because the object's density was equal to that of the fluid's as a result of the net force acting on the object being 0 which would then mean the…
FishFlops
- 145