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

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Question about Elon Musk's Hyperloop Suspension [closed]

So one of the proposed suspension systems that will be used on the hyperloop include the externally pressurised air cushions. These cushions lift (or atleast help lift) the capsule and reduce drag ...
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64 views

Cleaning a dirty jar [duplicate]

I would like to wash the inside of an almost empty cylindric jar on whose walls there are remains of a sticky substance such as peanut butter. I do this by filling it up with water and then shaking ...
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36 views

Sedimentation at the bottom of a vessel

At the moment I'm studying the sedimentation of suspensions. There is a lot of literature discussing the physics behind this processes (e.g., 1, 2, 3, 4). Most of the sources I found study only the ...
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25 views

Flow Rate Calculation from a drain tank through a pipe [duplicate]

I want to know how to calculate the flowrate (Q) of a drain tank flowing through a pipe (see the figure below) All I know is that Q=Velocity(V) x Area (A) V= sqrt(2*g*H)=sqrt(2*9.81*10)=14m/s. I ...
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Why can't the Navier Stokes equations be derived from first principle physics?

At the 109th UCLA Faculty Research lecture, Seth Putterman gave a talk on Sonoluminescence. During the lecture he emphasized that "The Navier Stokes equations cannot be derived from first principles ...
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Why do the tangent holes (like in pitot-static tube) feel the static pressure?

Why do the tangent holes (like in pitot-static tube) feel the static pressure although the static pressure is in the direction of the velocity of the streamlines not normal to the surface of the hole
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50 views

Pressure - How much fluid can void support?

Please refer to the attached (terrible) drawing while reading the post ! After watching some videos about the U-tube effect in drilling, a question came to me. Imagine one fluid of heavy density ...
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Specific form of Stokes's differential equation

Coming from a chemical background, I have next to no knowledge of the (as it seems to me) complex field of fluid dynamics, so bear with me here. I'm reading a paper written by seismologist Norman ...
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31 views

Frictionless and inviscid

In the book Fluid Mechanics by Robert A. Granger, there is a study question, 4.10, asking "How can frictionless real fluids exist and inviscid fluids not exist?" Could someone please explain? ...
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128 views

Why dont we consider force exerted by atmospheric pressure in mechanics?

My school has started teaching fluid mechanics, and it really bugs me why we don't consider force exerted by atmospheric pressure in mechanics. I couldn't understand a word my teacher said. There is ...
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58 views

Forces of suction in WIllie Wonka's Chocolate Factory (filmed 2005 starring Johnny Depp) [closed]

Before I begin the question: I am in no way judging this movie, just happened to be casually watching it and saw the scene (referred to below) and thought to post this question. The scene: Boy falls ...
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61 views

Direction of pressure forces on a control volume (surface)

According to http://www.mne.psu.edu/cimbala/Learning/Fluid/Pressure/pressure_basics.htm, "Pressure always acts inward normal to any surface (even imaginary surfaces as in a control volume).". ...
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120 views

Terminal velocity of a steel ball in water [closed]

I am investigating on the terminal velocity of steel balls moving in water. I used the balls with different diameters, such as 3.17mm, 6.02mm, etc. And I used a full-filled 1L graduated cylinder. I ...
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1answer
49 views

Would a linear relationship between pump speed and the flow rate from the pump be expected?

I am building a water cooling system for my pc whereby the water can be individually redirected to each of the three individual graphics cards depending on temperature. Can the relationship between ...
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1answer
37 views

Weather Meridians

Are there meridians that effect cloud movement? While observing radar images of moisture bearing cloud movements (at my location in Florida), I've noticed a splitting of the cloud formations a ...
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2answers
48 views

Why does simmering sauce make bubbles and how Is it different from boiling water

Why does simmering sauce makes bubbles at different places. Is this like boiling water? Why or why not?
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165 views

The optics of vortex (in water): why there is a bright ring?

This picture is from this YouTube video from "Physics Girl", which shows how you can generate vortices in a swimming pool by using a plate: And there she explains the creation of the shaded circle ...
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4answers
67 views

Is it possible to make a low dense object sink in a fluid of higher density by cutting the object in particular shapes?

As we know that pressure becomes greater with decrease of height in a liquid column. If an object having lower density than that of the liquid cut in a shape of a pyramid or a right circular cone is ...
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453 views

Swimming in a ball of water in space

What would I feel if I went swimming in a ball of water in space? Would I feel greater pressure as I went deeper into the sphere? What would it be like to swim in something like that? Also, let's say ...
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1answer
61 views

Can a vacuum make a turbulent flow laminar?

When a vacuum is generated next to a turbulence, does the flow towards the vacuum become laminar? Imagine a vacuum cleaner tube is put next to turbulent air movement, does the "suction" change the ...
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1answer
31 views

Darcy friction factor

I have an assingment that says: How is the friction factor $f$ dependent of the roughness $\epsilon$ and Reynolds number $Re$? The equaton for the friction factor is ...
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1answer
18 views

Can we agitate a classical non viscous fluid?

Suppose we have an infinite amount of a non viscous liquid (No boundary). Inside that liquid works a rotating impeller. Can the impeller agitate the liquid at all? The question arise from thinking ...
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1answer
26 views

In the non-Newtonian flow, what's the difference between Carreau–Bird model and FENE-P model

Can FENE-P model describe the shear-thinning or shear-thickening flow?
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52 views

How to solve Laplace equation in a domain with one boundary along a curve?

Is there a way to solve the 2D Laplace equation $\frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} =0$ on $0 <x<\infty$ and $0 < y < \infty$, such that the domain is ...
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1answer
41 views

What is the best way to calculate speeds at other points in a venturi-tube when knowing one?

I and a friend have made a venturi tube trough which water flows at a low speed. The flow is therefore laminar. We measured the static pressure using some piëzometers at the points 1,2 and 3. We know ...
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59 views

Why does the sound of my tea stirring go up in tone the faster I stir?

I've noticed that when stirring my tea, as I stir faster the tone generated by the stirring goes up. Why is that? Is it something to do with the Doppler Effect? EDIT -------------------------- ...
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1answer
54 views

By what factor would you have to slow down time for water to feel like glass?

I have been told that though glass seems like a solid, it is somehow, in theory, a liquid -- but is just somehow a liquid that is so thick that it appears to be solid. (Of course --- if this premise ...
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1answer
23 views

Are the arms of a hurricane along wind direction?

Within any tropical hurricane satellite photo we see a typical swirl pattern of clouds. Are the arms of clouds we see aligned on the winds vector field? Or are they on the contrary perpendiculars to ...
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2answers
28 views

Friction drag force

When an object moves through air, the air closest to the object’s surface is dragged along with it, pulling or rubbing at the air that it passes. This rubbing exerts a force on the object opposite to ...
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70 views

Can lift contradict conservation of energy?

In cruise flight of an aircraft lift does no work, it just holds the aircraft aloft. In order to climb aircraft pitch up and need excess energy because the thrust vector now has a vertical component ...
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100 views

Why does glue stretch straighter than string?

So I have some bottles of lemonade and I peeled the labels off both of them, revealing the glue underneath. When these bottles were next to each other the glue stuck. I pulled them apart and it forms ...
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36 views

Heat transfer between river and air

There is a temperature sensor about 200 feet back from a large river, at about the same height as the river. A sewage pipe continuously dumps water of about 12 degrees C in the river directly in front ...
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21 views

Fluid Dynamics applied to Aircraft wings [duplicate]

On aircraft wings, the bottom is flat and the top is curved. I know this benefits the aircraft by producing lift, but I wish to understand how. I'm told it has something to do with how fluids behave.
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What happens to the air in a water bottle when it falls?

(ignoring the air resistance that causes the bottle to take positions in mid air. Let's say it is dropped in a vacuum with earth's gravity accelerating it downwards) I just cannot catch what happens ...
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39 views

'Eulerian' description of a rigid body submerged in fluid

In this paper, equations of rigid body motion (eq 4 and 5 in the paper) are written in Eulerian form (eq 12 in the paper). The rigid body is submerged in a viscous incompressible fluid. ...
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2answers
42 views

Field theory for a finite temperature normal fluid

Can normal-fluid (not superfluid) hydrodynamics be derived from some classical field theory? Here I mean conservation (continuity) equations for mass (density), momentum, and energy (entropy, ...
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41 views

Find the force and the torque so that the cylinder is in balance

At the cylinder of the picture there are static pressures from environment fluid of density $\rho$. If we neglect the atmospheric pressure, calculate how much force and how much torque is needed so ...
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2answers
114 views

Incompressible Navier-Stokes pressure solve in simulations

I am a complete newcomer when it comes to fluid simulations. I'm currently working through some tutorials to understand the idea of of the discretized Navier-Stokes equations for numerical ...
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80 views

Fluid mechanics -Question about boundary?

Problem statement: A two-dimensional fluid stream of thickness $S$ and velocity $c$ (evenly distributed through the thickness of the stream) falls on a stationary plate and gets separated. Calculate ...
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1answer
35 views

Equation of a water pump with a nozzle

If I have a small water pump with a flow f (L/s) and maximal pressure p (bar) and attach its output to a small tube having on the other end a nozzle with an area A (m^2). What is the equation that ...
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How did we get rid of the term $\overrightarrow{G}_W$? [closed]

Equation of conservation of momentum: $$\frac{d}{dt}\int_{W}\rho \overrightarrow{u}dV+\int_{\partial{W}}\rho \overrightarrow{u} (\overrightarrow{u} \cdot ...
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Paradoxical Friction When Frying Eggs

I cook scrambled eggs for breakfast in an 8-inch diameter non-stick frying pan with sloping sides (approx 45 degrees). I cook the eggs in a lot of butter and bacon grease that is melted firest, so ...
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66 views

Area Integrals when Calculating Force Exerted by Air Pressure [closed]

I'm trying to find the force exerted on the walls of a cavity being filled with air. This involves doing area integrals, which I'm struggling with. The setup below is slightly complicated, see the end ...
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49 views

What happens when I open the door between 2 objects full with liquid, but with different center of rotation?

No gravity. Two disks are full of a liquid: water for example. Each disk rotates around its center of rotation. Disks rotate at the same angular velocity. Centers of rotation are not the same. Like ...
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mathematical Physics + fluid mechanics, thermodynamics + mass transfer? beginner [closed]

I am completely new to the world of physics and am interested in learning the aforementioned topics. I have previously studied biochemistry, but am fascinated by physics and am interested in ...
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2answers
45 views

Heating suprecritical water in a closed water tank

How does the pressure of water in a closed tank evolve in the following setting: - closed tank of 2 liters (filled up with water) - water initially at 25°C and pressurized to 3 bars The water is now ...
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48 views

Is vortex tube reversible? [closed]

If you inject cold and hot air in outlets of a vortex tube, do you obtain a greater pressure at inlet?
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1answer
83 views

In a fluid, why are the shear stresses $\tau_{xy}$ and $\tau_{yx}$ equal?

In solid bodies, $\tau_{xy}=\tau_{yx}$ makes sense to me because the volume elements "hold together" and can not spin against each other and therefore the resulting torque from the shear stresses has ...
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Confused on how to apply the volume integral form of the Biot-Savart law

In Viscous evolution of point vortex equilibria (Jing, 2011) the author explains that the velocity equation for the Lamb-Oseen vortex is found by applying the 2D Biot-Savart law to the vorticity ...
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Can water seep in?

Today morning I was sweating a lot, and a drop of it directly fell on my iPhone's home button. Considering the height of fall to be approx. $30 cm$, I started wondering whether water could seep in. ...