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

learn more… | top users | synonyms (1)

1
vote
0answers
99 views

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 ...
1
vote
0answers
64 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 ...
1
vote
0answers
33 views

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 ...
8
votes
5answers
218 views

Is there a definite boundary between a powder and a fluid?

Given a powder of solid substance what will happen if we make the granules smaller and smaller mechanically? Will this eventually make a liquid or gas from the powder? Can there be gaseous substanse ...
0
votes
0answers
29 views

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 ...
1
vote
0answers
85 views

momentum equation to find velocity of solid particle after collision [closed]

If a particle collides with a liquid drop, particle might penetrate into drop and so the velocity of particle reduces. i.e. a sudden change in particle velocity happens right at the collision moment, ...
1
vote
0answers
43 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?
1
vote
2answers
342 views

Steady flow in fluid dynamics?

Steady flow is the condition in which the flow velocity profile does not vary with time. Mathematically this is translated to $\frac{\partial \mathbf{v}}{\partial t} = 0$, for example in the ...
1
vote
2answers
37 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 ...
0
votes
0answers
45 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 ...
1
vote
0answers
35 views

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 ...
4
votes
1answer
77 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 ...
3
votes
1answer
131 views

How does a hollow-point bullet move smoothly through the air, presenting a 'cup-shaped' nose instead of an actual sharp-point to the fluid?

Hollow-point rounds move smoothly through the air when presenting a 'hollow cup-shape' instead of a traditional 'sharp point' to the fluid air. Does this mean the air trapped, and at some assumed ...
4
votes
2answers
252 views

Does water maintain equal level in connected vessels?

Consider a system as illustrated below: There are two 55 gallon barrels used to store water coming down the gutter. These barrels are connected together on the bottom to maintain equal water level ...
1
vote
1answer
244 views

Capillary action meniscus height in a tube fitted inside another tube?

I was thinking about how would capillary action change in a tube (classic example) and in a tube fitted inside another tube (considering water as the liquid involved). Height of liquid column: ...
3
votes
1answer
153 views

I would like to know what variables to consider when I experiment with pouring from bottles and the “glug” effect?

I am a middle school science teacher and want to model a science fair project for my students. Specifically I want to investigate using a vent in the top of the handle of a gallon milk jug to ...
1
vote
0answers
24 views

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. ...
7
votes
3answers
488 views

Why does the lake surface appear darker in some areas?

What causes the surface of the lake to appear darker in some places? Firstly, I know that it's not fishes that cause it. Secondly, the dark surfaces move from time to time and thus are not ...
4
votes
2answers
7k views

Calculate fluid pressure loss due to hole leakage

I have a cylindrical pipe of internal diameter of around 5mm, with pressurised fluid flowing though it. If I have holes at the wall of the pipe, how do I calculate the pressure loss due to water ...
2
votes
1answer
28 views

Effect of small changes in atmospheric pressure on open cylinder piston

OK, I'm not a physics student, but I played one for 2 semesters 35 years ago... now I'm a competitive shooter working a theory about why small changes in atmospheric conditions cause our hyper-tuned ...
2
votes
1answer
48 views

Finding velocity field of spherical bubble in incompressible fluid

I have the following question: A spherical bubble in an incompressible fluid of density $\rho$ has radius $a(t)$. Write down an expression for the velocity field at a radius $R > a$. The pressure ...
1
vote
0answers
10 views

Increased pressure of Liquid Pitch and Limestone (Bitumen/Asphalt) @ approximately 300 degrees Fahrenheit

If liquid pitch and limestone (20/80 mostly limestone) is pumped (appx. 5 gpm) out of a nozzle that restricts the flow compared to the flow that would be achieved straight out of the pump ( no ...
0
votes
1answer
27 views

Nozzle vs Orifice Water Jug Draining

why is this happening? Water jug draining So why does the water drain faster when you drain a jug through a funnel compared to the hole you make at the bottom of a jug( the hole is the same size as ...
0
votes
1answer
58 views

How do compressible fluids behave near a sink?

Imagine there is a large spherical tank of a fluid floating in space. There is a small pipe from the outside to the inside that opens in the center of the spherical tank and lets fluid out at a ...
3
votes
1answer
176 views

Fluid dynamics tsunami

I have been given a energy head (pressure) in meters for a given tsunami on land. If the tsunami hits a wall 1 meter by 1 meter, is it possible to calculate the height it will reach. I am thinking it ...
1
vote
0answers
121 views

Can one model a spiral galaxy with a similar manifold to one for a whirlpool?

My question is more of a phenomenological question than literal, since the forces involved are very different. When one looks at the distortions (or wrinkles or whatever you wish to call them) in the ...
0
votes
0answers
44 views

Flow rate Calculation with Pipe Diameter and pressure?

I am using a constant Diameter pipe from a motor to a machine for oil flow.A pressure trasmitter is kept near the machine to know the pressure.So can we calculate the Flow rate using the parameters ...
0
votes
2answers
127 views

Fluids in U-shaped Tube

In a U-shaped tube, water and oil are separated by a movable membrane. What is the ratio of the heights $\frac{h1}{h2}$ (density of the oil $ρ_{oil}$ = 0.92 $\frac{g}{cm^3}$)? I tried solving by ...
4
votes
1answer
136 views

Kolmogorov/Energy spectrum for turbulent boundary layer

Previously, I have calculated energy spectrum for 3D isotropic turbulent flow data which is equally spaced in all three directions and then to compute the energy spectrum, one performs Fourier ...
0
votes
1answer
20 views

the different settling speed of two solid particles in fluid

In a container full of fluid A, which can be water or oil, I have two solid particles, both of which are of the same material. These two particles are of different size. One is bigger than the other ...
4
votes
2answers
91 views

Is Torricelli's law “wrong” for big holes? - Tank draining problem

Consider a tank full of water with a constant cross-sectional area A1 placed vertically on the ground. Now someone drills a hole of an area A2 in the bottom of the tank, and the liquid starts escaping ...
1
vote
0answers
42 views

Pumping water from a well [closed]

I have water well $h_1=70~m$ below ground level. A cylindrical tube of diameter $e$ joins the well to a tank of height $h_3=10~m$, $h_2=1.5~m$ above the ground. The tank is initially filled with water ...
1
vote
2answers
792 views

Difference resultant aerodynamics force on an airfoil and a flat plate

From basic airfoil theory the following free body diagram can be determined for a two dimensional asymmetric airfoil: Here the direction of the resultant force is governed by the geometry of the ...
0
votes
0answers
40 views

Pool full of Jell-O

Imagine I have filled my backyard swimming pool (8 feet deep) with a solid block of Jell-O. What would happen if I tried to swim in it? My understanding is that the viscosity of the "water" doesn't ...
6
votes
2answers
113 views

What is the curve described by the water of a wet spinning tennis ball?

I'm looking at this picture from this site and I'm curious about what is the curve described by the water. The involutes $$x=r\left[\cos(\theta+n)+\theta\sin(\theta+n)\right]\\ ...
0
votes
0answers
74 views

Why Does Moving a Cup of Coffee Up and Down whilst carrying it Make it less Likely to Spill?

Sometimes I have a Very Full Mug of Coffee and I am trying to carry it without it spilling. I noticed that if I moved the Mug up and down when carrying it, it seemed to settle the coffee and make it ...
8
votes
3answers
5k views

What about negative Pressure?

Here is something I see : Let's say the ideal fluid(water here) of density $\rho$ is drawn from a source by a motor and thrown upwards with a velocity $v$. Now we take the power of motor be ...
1
vote
2answers
747 views

Efflux speed of ideal fluid dependent on diameter?

I have a cylinder full of water with diameter $D$ with a round opening on the bottom with diameter $d$. The water is friction-free and incompressible. Now I need a relationship for the efflux speed ...
1
vote
2answers
104 views

Silicone tube with three holes, flow rate, pressure

I have a silicone tube -- a saline solution flows in from one end, and then flows out of three holes of equal diameter and equal distance from each other that are along the side of the tube. What can ...
2
votes
0answers
35 views

Fluid flowing into small pores

I have some open porous foams with pore sizes ranging from 50-100nm. I want to flow water into this structure but even at 30 atmospheres it would NOT go in. I am looking for a way to calculate the ...
7
votes
1answer
105 views

Wavy stream of liquid

When pouring a liquid into a glass some streams have a wavy shape, like the one in the following photo: (Couldn't find a better picture, sorry.) What causes the stream to be of such a shape?
11
votes
3answers
14k views

Why does water pouring from a glass sometimes travel down the side of the glass?

If you have a glass of water, say, three quarters full and you pour it at an angle of say, $45^{\circ}$ with respect to the the table, the water comes out of the glass and goes directly down towards ...
11
votes
2answers
209 views

Why pouring milk from a height makes a chain shape? [duplicate]

I have noticed a chain-like shape when milk is poured from a height into a cup. Actually the chain pattern repeats itself after some distance and again till it reaches the milk in the cup. Any ...
2
votes
0answers
27 views

$L^p$-weighted enstrophy calculations

Mathematician here, only somewhat familiar with physics, but finding myself involved in a research project on fluid dynamics. I'm studying a 3D simulation of turbulent fluid flow, and we are currently ...
1
vote
0answers
32 views

What is a diffusionless fluid?

I'm taking a course in astrophysical fluid dynamics and have come across a problem involving "small diffusionless disturbances" of a fluid. Based on the nature of the course I expect the examiner to ...
1
vote
0answers
37 views

Volumetric flow rate as a function of radius of pipe [duplicate]

I have a container (assume open on top) with $1m^3$ of water. That water exits this container from an opening that has a cross-section area A e.g. $πR^2$ = $1cm^2$. What is the volumetric flow rate ...
1
vote
1answer
35 views

Applying unsteady Bernoulli (to a balloon attached to a tube)

Using Bernoulli’s equation for an unsteady irrotational motion of an inviscid incompressible fluid, solve the following: Water of density $\rho$ is driven through a horizontal tube of length $L$ and ...
2
votes
1answer
37 views

Bernoulli Equation for isentropic ideal gas flow

If one derives the Bernoulli Equation for the isentropic ideal gas flow you get: $ \frac{1}{2}v^2 + g z + \left(\frac{\kappa}{\kappa -1} \right) \frac{p}{\rho} = const. $ Two questions: Is ...
12
votes
5answers
774 views

Compressibility and the form of Newton's second law in fluid mechanics

In deriving Euler's equations for fluid mechanics, in particular $$f=\rho \partial_t v +\rho v\cdot \nabla v$$ for some body force $f$ (e.g Landau & Lifschitz 2.3) one assumes the continuity ...
1
vote
1answer
79 views

Why bodies lose heat faster in water than in air?

A simple question. In several places, including this very recent and already famous paper http://www.sciencemag.org/content/348/6236/786.short it is stated that bodies lose heat in water very fast ...