The quantitative study of how fluids (gases and liquids) move.
6
votes
2answers
120 views
Could some design of a propeller be used in both air and water?
Propellers in water are smaller in diameter. They also move more slowly. On the other hand, aircraft propellers are larger in diameter, have narrower blades and operate at very high speeds. An ...
0
votes
0answers
33 views
Curls in water taken in a liquid [duplicate]
Consider a beaker having a hole at the bottom at its geometric centre is connected to a pipe which is closed initially. Water is filled when the pipe is opened I saw curls are being formed. Why they ...
1
vote
1answer
53 views
Force required to move a fluid out of piston at depth
I have a cylinder filled with water in it at the bottom of the ocean. Say 100 meters down. In this cylinder is a piston that moves up and down. Its job is to squish the water out the bottom of the ...
1
vote
0answers
34 views
What temperatures can be reached in an air-to-air thermocompressor nozzle and why?
People are generally of the opinion that the boiler injector cannot be redesigned to run on air. In other words, an air-to-air thermocompressor that puts fresh air into a tank without a mechanical ...
1
vote
1answer
92 views
Does gravity affects temperature reading of a mercury thermometer?
I remember when I was in primary school, the science teacher put me in charge of a mercury thermometer. I do not quite understand the mechanics behind except that mercury expands when it is hot and ...
1
vote
0answers
49 views
Calculating pressure in accelerated fluids in closed and open vessels?
The question asked was "what should be the acceleration such that the pressure at both the points marked by thick dots be equal? the vessel is open and cubic with side 5m?"
Initially i considered ...
1
vote
1answer
95 views
Concerning drag on a flow past a cylinder
I am wondering about the drag coefficient for a flow past a cylinder. I am reading this article.
I understand why the drag is high to begin with (point 2), when the boundary layer separates and the ...
0
votes
2answers
110 views
Will this type of engine produce thrust?
I was wondering that if I create a engine as shown below in the image will it produce any kind of thrust or it is a complete junk?
2
votes
2answers
115 views
Whats the anti-torque mechanism in horizontal take-off aircraft?
In most helicopters there is the anti-torque tail rotor to prevent the body from spinning in the opposite direction to the main rotor.
What's the equivalent mechanism in horizontal takeoff single ...
3
votes
1answer
292 views
Exact Solutions to the Navier-Stokes Equations
There are a number of exact solutions to the Navier-Stokes equations. How many exact solutions are currently known? Is it possible to enumerate all of the solutions to the Navier-Stokes equations?
6
votes
2answers
148 views
Why water in the sink follow a curved path?
When you fill the sink with water and then allow the water to be drained, the water forms a vortex.. And then it starts to follow a curved path downwards by effects of gravity..
Why this phenomena ...
0
votes
3answers
107 views
Navier-Stokes system
I have to study this system which name is Navier-Stokes. Can you explain please what means that $p$, $u$ and $(u \cdot \nabla)u$. What represents in reality? Tell me please, how should I read the ...
2
votes
2answers
140 views
Hot Air Balloon and Buoyancy
This is a conceptual question in a solution I am trying to understand.
Problem statement:
I have a balloon with a volume of V $m^3$. The outside air temp is $K$ kelvin
and mass to lift is $m$ kg.
I ...
2
votes
1answer
55 views
Work done by gravity on Water
Now according to me we would see change in potential energy of system and equate it to the work done by gravity.
But when we see this the first column lowers by $H/2$ and right one rises by $H/2$ ...
0
votes
0answers
25 views
how to explain the upright force for the plane? [duplicate]
I remember in the high school physics, my teacher told us that the design of the plane wing is because we want the air above the wing flowing faster than the air flowing below so the pressure above ...
5
votes
2answers
250 views
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 ...
1
vote
0answers
46 views
Physical interpretation of an intermittency definition
A random function $v(t)$ is said to be intermittent at small scales of its "Flatness" $F$, given as
$$
F(\Omega) = \frac{\langle (v_{\Omega}^{>}(t))^4\rangle}{\langle ...
2
votes
5answers
148 views
How does an aeroplane maintain balance during maneuvers?
I understand the principle behind flight, how the lift is generated etc. What I don't understand is when there are maneuvers made where the plane flies such that the wings are in vertical plane, how ...
3
votes
3answers
93 views
Spinning liquid to create a centrifuge effect
I'm in the business of purifying used cooking oil. Normally, I heat the oil up and let it settle for a couple of days. Water and solids settle to the bottom and cleaner oil remains on top. I'm trying ...
3
votes
1answer
66 views
Equidistant coffee rings in a mug: pinning boundaries coupled with migration of solute or just sip volume?
I understand that you get coffee rings on a table as a result of solute migration (solutocapillarity) towards the pinning of the circumference of the coffee ring [Deegan et al.].
Below is an ...
0
votes
0answers
48 views
Air flow in tube with smaller perforated holes balance
Given: I have a $1.5$ diameter tube that I'm pushing air through that has perforated holes along its length, and the far end is closed. Air leaves 10 perforated holes to atmosphere. Temperature is ...
1
vote
0answers
22 views
blood fluidics - can you determine the force exerted on a bound red blood cell under shear stress?
Is it possible to calculate the force exerted on a bound, infected red blood cell under various shear stresses? The strength of an adhesive interaction is normally measured by SPR or AFM, however ...
4
votes
1answer
140 views
Lagrangian Coordinates in Fluid Flow
I apologize if this is not the right place to ask this question:
I am currently reading a paper by Y. Brenier, where for the fluid flow he introduces a Lagrangian label $a$ instead of the vertical ...
4
votes
1answer
171 views
Can a hovering helicopter travel half the globe in 12 hours? [duplicate]
Suppose we have a helicopter that is able to stay stationary in flight for extended periods of time. If such a helicopter stayed at point A in the sky for 12 hours straight, would it reach the other ...
1
vote
1answer
288 views
Archimedes principle and specific gravity
A physical balance measures the gravitational mass of a body. I conducted an experiment to find out the specific gravity of a bob. I first measured the mass of the bob in air, and then in water. The ...
1
vote
1answer
89 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 ...
4
votes
2answers
106 views
Best shape to reduce the splash of a droplet?
Our coffee machine catches the last couple of droplets, after your cup is removed on a shape to reduce plash of the coffee droplets.
These shapes are placed inside the spill reservoir.
The shape ...
0
votes
1answer
62 views
Can anyone explain what a superleak is?
In the context of Helium can anyone explain what a superleak is and why it could be useful?
1
vote
0answers
29 views
where to find sample fluid stirring data?
I want to find some force data for fluid stirring. Originally I intended to record the data using my force sensor, but it doesn't have the resolution to read stirring force for Newtonian fluid.
...
3
votes
2answers
88 views
What causes acceleration of particles in the expansion section of a De Laval nozzle?
A De Laval nozzle has a compression section, where the propellant is compressed (and thereby accelerated) as it moves towards a narrow section (the throat). After the throat, the nozzle widens out ...
2
votes
0answers
96 views
Conformal symmetry of Navier-Stokes?
This question is in reference to the paper arXiv:0810.1545
Can someone help understand this scaling argument and the proof(?) that there is a conformal symmetry in Navier-Stoke's equation? (..am I ...
1
vote
0answers
74 views
Wall pressure of a fluid flow in a pipe of variable radius
Using all cylindrical coordinates, pipe with z-axis vertically upward and radius of $r = G(z)$, flow is incompressible, inviscid and steady, Using appropriate boundary conditions I want to find the ...
16
votes
2answers
240 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 ...
5
votes
1answer
160 views
Drag on a spinning ball in fluid
I am a physics newbie (high school level) and I am wondering what happens when a spherical object is spinning on the spot in a bunch of gas (no gravity here, just an imaginary physics sandbox).
Am I ...
0
votes
0answers
141 views
pressure loss in a syringe
I'm currently working on a problem which is really giving me some issues.
The problem concerns the force required to expel water from a syringe. We have a 20ml syringe (which is $2\times10^{-5}$ ...
2
votes
2answers
50 views
Flux Over a Surface
I am teaching a multivariable calculus course and we are starting to go over surface integrals. I am a math professor with little knowledge of physics. At one point the book discusses fluid flow. ...
0
votes
1answer
57 views
Buoyancy fluxes in a stratififed fluid and units
I am calculating the buoyancy flux (B) for a stratified fluid as follows:
where g = 9.81 m/s; alpha = 1.6 x10^{-5} + 9.6 x10^{-6} x (20 degC); S = 100 Wm^{-2}, p0 = 1000 kg/m3, and Cpw is the ...
5
votes
1answer
213 views
What is the mystery of turbulence?
One of the great unsolved problems in physics is turbulence but I'm not too clear what the mystery is. Does it mean that the Navier-Stokes equations don't have any turbulent phenomena even if we solve ...
1
vote
1answer
153 views
Proof that flux through a surface is independent of the inner objects' arrangement
$$\Phi=\iint_{\partial V}\mathbf{g} \cdot d \mathbf{A}=-4 \pi G M$$
Essentially, why is $\Phi$ independent of the distribution of mass inside the surface $\partial V$, and the shape of surface ...
1
vote
1answer
380 views
Determine viscosity using falling sphere (Stokes Law, Ladenburg correction)
Introduction
I am trying to determine the viscosity of a fluid. Therefore, I let a sphere of known mass m and radius r fall ...
1
vote
2answers
153 views
Whirlpools and Tornados
This may not be a great question. But whenever you drain water, a small whirlpool happens, obviously. This got me thinking...
Can we model tornados with this effect, would it even be beneficial?
2
votes
1answer
92 views
Bernoulli's theorem: $\frac{p}{\rho}+\frac{1}{2}u^2+\phi$ is constant along a streamline
I am trying to understand the Bernoulli's theorem:
$\frac{p}{\rho}+\frac{1}{2}u^2+\phi$ is a constant along a streamline
I got that:
$\frac{\partial u}{\partial t}$ + ($\nabla \times u)\times u$ ...
1
vote
1answer
129 views
how to determine if a vortex is laminar or turbulent
In a cylindrical chamber with a high diameter-to-height ratio; a fluid is tangentially injected. there is an axial exit to the cylinder.
how do I determine if the vortex so formed is laminar or ...
3
votes
2answers
109 views
Pumping water from a closed column. Will the column get empty or just circualte?
As a picture is worth a thousand words, here is my problem:
It is a closed water column with a bit of air in the top section.
If I run the pump and make the water flow from IN to OUT,
Will the ...
0
votes
1answer
85 views
What does Euler equation mean?
In order to prove the Bernoulli’s principle ($\frac{p}{\rho} + \frac{1}{2}u^2+\phi = constant$ ), I have to use the Euler equation: $\frac{Du}{Dt} = -\frac{1}{\rho}\nabla p + g$.
I know how to prove ...
2
votes
0answers
78 views
Difference between a Fixed Point and a Limit Point in implementations of the Renormalization Group (RNG) in Large Eddy Simulation (LES) model
In the introduction of this paper, it is explained that and how the application of a dynamic subrid scale model for turbulence into a large eddy simulation (LES) model corresponds to doing one ...
1
vote
2answers
60 views
Membrane that allows liquid to pass only when forced under pressure
Is it possible to have a membrane that will not let a liquid through it at normal pressures due to gravity, but pass that liquid when substantially pressurised?
For instance, a few inches of water ...
0
votes
1answer
90 views
Water, how do you make ripples
How do I make a ripple effect in a bowl of water. I have tried throwing small pebble sin but it just splashes and sinks. I have read that I need to make the water a thicker liquid ie add glycerine, ...
2
votes
1answer
135 views
0
votes
0answers
46 views
Water Stream from a Horizontal Surface
If water was projected from a flat surface where gravity was equal all over the surface. What would happen when the water fell in on itself? The water is in a continuous stream and is perfectly ...
