# Tagged Questions

The quantitative study of how fluids (gases and liquids) move.

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### 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 ...
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### 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 ...
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### 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 ...
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### Will this type of engine produce thrust?

I was wondering that if we replace the combustion chambers in a jet engine with heaters heating the compressed air up to temperature near to plasma then what will be the case, will it produce any kind ...
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### 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 ...
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### Exact Solutions to the Navier-Stokes Equations [closed]

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?
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 $H/2$ and ...
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### 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 ...
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### 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 ...
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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 v_{\Omega}^{>}(t))^2\... 4answers 2k 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 ... 3answers 468 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 ... 1answer 146 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 ... 0answers 61 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 ... 1answer 383 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 ... 1answer 530 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 ... 1answer 3k 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 ... 2answers 1k 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 ... 2answers 495 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 ... 1answer 550 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? 0answers 45 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. ... 2answers 2k 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 ... 0answers 217 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 ... 0answers 322 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 ... 2answers 503 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 Glass ... 1answer 4k 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 ... 1answer 1k 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 20 ml syringe (which is 2\times10^{-5} ... 2answers 277 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. ... 1answer 142 views ### Buoyancy fluxes in a stratififed fluid and units I am calculating the buoyancy flux (B) for a stratified fluid as follows:$$ B=\frac{g\alpha S}{C_{pw}\rho_0} $$where g = 9.81 m/s; \alpha = 1.6 t\times10^{-5} + 9.6\times10^{-6} \times (20 \... 4answers 9k views ### What is the mystery of turbulence? One of the great unsolved problems in physics is turbulence but I'm not too clear what the mystery is. Does it mean that the Navier-Stokes equations don't have any turbulent phenomena even if we solve ... 2answers 528 views ### Proof that flux through a surface is independent of the inner objects' arrangement$$\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 $\... 2answers 10k views ### Determine viscosity using falling sphere (Stokes Law, Ladenburg correction) Introduction I am trying to determine the viscosity of a fluid. Therefore, I let a sphere of known mass m and radius r fall (... 2answers 707 views ### Whirlpools and Tornados This may not be a great question. But whenever you drain water, a small whirlpool happens, obviously. This got me thinking... Can we model tornados with this effect, would it even be beneficial? 1answer 300 views ### Bernoulli's theorem:$\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$=... 1answer 2k views ### how to determine if a vortex is laminar or turbulent In a cylindrical chamber with a high diameter-to-height ratio; a fluid is tangentially injected. there is an axial exit to the cylinder. how do I determine if the vortex so formed is laminar or ... 2answers 636 views ### Pumping water from a closed column. Will the column get empty or just circualte? As a picture is worth a thousand words, here is my problem: It is a closed water column with a bit of air in the top section. If I run the pump and make the water flow from IN to OUT, Will the ... 1answer 495 views ### What does Euler equation mean? In order to prove the Bernoulli’s principle ($\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 ... 0answers 150 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 ... 2answers 877 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 (... 1answer 461 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, ... 1answer 675 views ### Flow in parallel paths after pressure regulator Consider the following: ... 0answers 86 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 ... 1answer 2k views ### Wave propagation in an incompressible flow Incompressible approximation of fluid flow is usually known to be lame in modeling the propagation of any disturbance in it, predicting a speed equal to infinity for the propagation of the ... 1answer 105 views ### Query about Bernoulli's principle We know that the lower atmosphere has high pressure and as we go up, the pressure decreases, if it's so then why doesn't all gases fly up into the upper atmosphere from the lower following Bernoulli's ... 1answer 129 views ### Explanation for the next steps of lamb-chaplygin dipole Can someone explain me the steps please (I mean steps 2 and 3)? I didn't understand it. 1) Any flow field represented by a stream function$\psi$(x,r), defined as: v = -$\frac{\partial \psi}{\...
Is the angle of attack of a rectangular wing influenced by the dihedral ($\Gamma$) of the wing? If e.g. a wing exists with $\Gamma$ = 0$^{o}$ it has angle of attack $\alpha$. If the dihedral is set ...