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

learn more… | top users | synonyms (1)

1
vote
2answers
325 views

Aerofoil Theory Project [closed]

I'm doing a project (dissertation) on the mathematics of Aerofoil Theory. I wonder if I could get some advice on a possible structure. I'm new to fluid dynamics, so it's quite hard to know where to ...
0
votes
0answers
19 views

Solve unsteady-state pressure-falloff axial gas flow equation for permeability

Equation 17 in Section 6.2.1.2 of American Petroleum Institute Recommended Practices 40 for Core Analysis gives a permeability equation of: $$ ...
8
votes
1answer
327 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 ...
2
votes
0answers
46 views

Is it possible to generate one half of a Karman Vortex Street?

The Karman Vortex Street is a type of phenomenon which is generally illustrated by examples in which a long, solid, smooth circular cylinder moves at constant velocity through a fluid. The long axis ...
1
vote
0answers
55 views

Basic fluid mechanics question on the FME

Ok, so I've got a question on a basic fluid dynamics question regarding the force-momentum equation (I don't know how common that phrase is, it's the one used in the textbook I have, but basically the ...
2
votes
0answers
51 views

How can we theoretically calculate the number of balloons needed to stop a bullet?

After watching this video, I am interested in proving it mathematically. The problem is that how can we apply the conservation of momentum here to find the velocity of the bullet while we don't know ...
1
vote
1answer
66 views

How size of objects lifted by the wind depends on the speed of the wind?

What are the sizes of the objects that could be picked up and flown by tornados, depending on the tornado's speed? To put it another way, assuming turbulent flow and object density much higher than ...
0
votes
1answer
142 views

Problem regarding Archimedes Principle [closed]

A small amount of mercury is filled into massless cylindrical test tube with an even bottom and length $l=0,200m$. The test tube is put into a large swimming pool filled with water. a) How ...
1
vote
2answers
129 views

Why can we produce a sound by blowing across a blade of grass, a paper strip or similar

I just don't know how is the sound produced? Does it come from the vibration of the blade of grass or the air in the up and down?
23
votes
3answers
4k views

Is this really a golden ratio spiral?

In this blog post, I found this picture: Tehre are other similar photos: and Does the water really form golden ratio spiral in such cases? Or is the photo just a provocative example, without ...
1
vote
3answers
75 views

What really is “inertial force”?

In Fluid Mechanics we often see the term inertial force when discussing Reynolds number. The problem is, I didn't really get what's this inertial force. Basically, the notion of inertia I have is that ...
0
votes
3answers
62 views

What forces of stress really represent?

I'm studying fluid mechanics and the book says the following: For any continuum, forces acting on a piece of material are of two types. First there are forces of stress, whereby the piece of ...
2
votes
1answer
745 views

Book recommendations for fluid dynamics self study

I have my bachelors degree in engineering science: computer science, option electrotechnic. I have a good understanding of basic mechanics and dynamics, calculus (differential equations). The books ...
0
votes
0answers
21 views

Good books for fluid mechanics [duplicate]

Hi everyone I'm new to this web-site. Over the years I have become more and more interested in applied fluid mechanics. Specifically nano to micro fluidics. As a chemist my mathematical background ...
24
votes
7answers
13k views

Why do tsunami waves begin with the water flowing away from shore?

A sign of a tsunami is that the water rushes away from the shore, then comes back to higher levels. It seems that waves should be both + and - polarized and that some tsunamis should go in the ...
0
votes
1answer
55 views

Properties of Fluids-theoritical confusion

I am having a very basic confusion on how we calculate the height of atmosphere when we assume that the density does not change with altitude(density remains 1.29 kg/m$^3$). I want to know why we say ...
0
votes
1answer
35 views

The name of effect of liquid flow inducing flow to neighboring layers of liquid?

How do you call an effect, when liquid or gas stream is involving the neighboring layers of matter also move? Like on videos of rocket engines testing, when exhausting gas sucks an air and steam from ...
1
vote
1answer
128 views

What is the differential equation for pressure in a container with an orifice?

I've seen similar problems all over physics.SE and other sites. Most of the time it is about non-compressible fluids, or not about the differential equations. The physical system of interest is ...
9
votes
3answers
317 views

Why do rain waves form and what is their connection to the texture of the surface they're on?

When it rains and water flows down an inclined street, ripples may form that are carried along with the current. Here's a picture with an example of what I'm talking about I'd like to know what the ...
1
vote
0answers
31 views

Ripples of flowing water on a smooth road surface [duplicate]

Yesterday some friends and I were walking in the rain. We noticed that, on a smooth tarmac road surface, the sheet of water flowing down the road was forming ripples as it went. Why was it doing ...
1
vote
1answer
166 views

Can I use Runge-Kutta to solve these equations?

Edit: I'm going to give some more background and derivation to show how I got to these equations. I am basically following the derivation that is found in the appendix of the following paper: ...
1
vote
2answers
59 views

Is viscosity a function of density only?

I know viscosity is also a function of temperature, but (excluding superfluids) are there any fluids which are less viscous than fluids at lower densities? Is density the ultimate control on ...
128
votes
7answers
19k views

What really allows airplanes to fly?

What aerodynamic effects actually contribute to producing the lift on an airplane? I know there's a common belief that lift comes from the Bernoulli effect, where air moving over the wings is at ...
0
votes
1answer
66 views

The Bernoulli equation: positive and negative sign problem

According to bernoulli equation $$ P_1+1/2 \rho v_1^2+ \gamma h_1= P_2+1/2 \rho v_2^2+ \gamma h_2. $$ Because $$ v_1=0\quad h_1=0 $$ So $$ 0= 1/2 \rho V^2+ \gamma h. $$ It is wrong I know, but ...
7
votes
4answers
21k views

Why can't helicopters reach mount everest?

Is there a reason why people can't just take the helicopter to mount Everest? Why is it that helicopters can't reach that high?
3
votes
2answers
564 views

What air pressure is needed on mars, to have fluid water?

The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi), about 0.6% of Earth's mean sea level pressure. There is a lot of frozen ice on mars, but it can't melt, because of ...
1
vote
4answers
2k views

What is the principle behind centrifugation?

What is the principle behind centrifugation? I understand the idea that you spin something around the centripetal force will cause an apparent force on the spinning system. However I don't quite ...
0
votes
0answers
53 views

Invariant Form of The Material Derivative

Why is the RHS of the following equation invariant to coordinate transformation and the LHS is not? And is there a way to show the equivalency between the LFS and RHS? \begin{align} \vec{V} \cdot ...
0
votes
2answers
46 views

Hydrodynamics: Conservation of momentum violated by a fan in a cylinder?

Consider the following situation: there is a hollow cylinder with both caps removed. The cylinder is submerged into water. Inside the cylinder, we place a fan (or pump) that pumps the water through ...
0
votes
1answer
63 views

How does a faucet work? [closed]

Well I mean how exactly water flows to the sink. How is it pulled through the faucet?
4
votes
0answers
65 views

What is the source of water and waves on the water planet in the movie Interstellar?

We will ignore some of the more obvious issues with the movie and assume all other things are consistent to have fun with some of these questions. Simple [hopefully] Pre-questions: 1) If the water ...
21
votes
2answers
1k views

When a drop of water falls into water, where do the splashes come from?

When a drop of water falls into a reservoir of water from a high enough altitude, water droplets will splash (image credit): My question: Does the water in those droplets come from the original ...
2
votes
3answers
8k views

About an upside down cup of water against atmosphere pressure

There is an experiment we learned from high school that demonstrated how atmosphere pressure worked. Fill a cup of water and put a cardboard on top of it, then turn it upside-down, the water will not ...
1
vote
0answers
34 views

How can one calculate diffusion velocity given the diffusion coefficient?

I am creating a basic simulation of 2-D diffusion and was wondering how diffusion velocity of a particle can be calculated if the diffusion coefficient is known (using no other information). Is this ...
7
votes
2answers
571 views

Why aren't airplanes like golf balls?

Ok this is a silly question but here it goes Although it is good to have a laminar flow of the air around the object for low drag but the laminar flow is prone the phenomena called separation (sounds ...
0
votes
0answers
11 views

Equivalence of Bulk Modulus Definitions [duplicate]

Per http://en.wikipedia.org/wiki/Bulk_modulus, $K=-V\frac{\mathrm d P}{\mathrm d V}$ and $K=\rho \frac{\mathrm d P}{\mathrm d \rho}$ are two equivalent definitions for $K$, the bulk modulus. How do ...
0
votes
2answers
47 views

Create air stream from heat

We know that heating the air inside a bounded box raises its pressure. And if there is a hole in the box, then air flows out until the pressure inside and outside balances. So in this case we would ...
9
votes
3answers
758 views

Would a perfectly clean and perfectly smooth champagne glass have no bubbles?

My understanding is that nucleation sites for bubbles in a champagne glass are either due to defects in the glass or due to fibers in the glass. (See this article for details on that statement.) Does ...
3
votes
3answers
79 views

Why do square shaped cups spill easier than round cups?

I've noticed that when I use a cup that is square shaped with convex sides, it spills more easily than a circular cup. Why does this happen? What is the most spill-prone cup shape? What is the most ...
0
votes
2answers
92 views

Liquid placed in a rotating cylinder

The Question A closed vertical cylinder is filled with an incompressible liquid of mass m completely. The cylinder is now sealed from all sides and rotated about ...
3
votes
6answers
31k views

Relation between pressure, velocity and area

In a nozzle, the exit velocity increases as per continuity equation $Av=const$ as given by Bernoulli equation (incompressible fluid). Pressure is inversely proportional to velocity, so we have lower ...
1
vote
0answers
76 views

Lattice Gas Cellular Automata - HPP model square lattice

In the HPP model of LGCA, a square lattice is used and there is only one collision configuration as mentioned in figure (taken from the book Lattice Gas Cellular Automata and Lattice Boltzmann models ...
1
vote
0answers
58 views

How does a sonic black hole (or dumb hole) work?

I came across this term and I heard they used sonic black holes to detect something analogous to hawking radiation, but I have failed to find sources which explain how exactly they work and how they ...
3
votes
1answer
249 views

The original thorium reactor?

With lunar thorium being common, and heavier than iron or nickel, does earth's core have the the occasional nuclear reaction?
2
votes
1answer
220 views

Thought experiment about fluid mechanics (reductio ad absurdum)

In an interview a philosopher said: "Suppose I cut the handle off your coffee mug leaving two holes. Would the coffee flow out of one hole faster than the other? If we tried to figure this out by ...
4
votes
2answers
56 views

Water level of ice in cup [duplicate]

Since ice is less dense than water, it floats on it, we all know this. Now suppose, if ice is floating in a glass cup, when the ice melts there should be some change at water level in the glass cup. ...
2
votes
2answers
1k views

How much water must flow trough canal to maintain a constant water deep?

In order to maintain a constant water deep in canal, how much water must flow trought the pipe ? As shown on picture, canal have a rectangular shape. I don't know if canal length have an influence. ...
4
votes
1answer
110 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
4answers
270 views

Pressure in fluid mechanics of incompressible liquid

Most liquids can be approximated to be incompressible, since the Mach-number is much smaller than 1. That means that the density variations are negligible and from the relation between pressure p and ...
1
vote
1answer
289 views

Calculating water flow as function of the height of water above the inlet pipe [closed]

The Source of Water is Pond where the water level do change randomly. A pipeline of 200mm pipe diameter run for around 2500 m. The Height difference between the level of the inlet pipe and the level ...