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

learn more… | top users | synonyms (1)

2
votes
2answers
29 views

Surface tension and soap bubbles

In a common experiment, you can make a paper clip float on water due to the strong surface tension. Adding just a tiny bit of soap immediately destroys the surface tension and lets the paper clip ...
1
vote
0answers
17 views

In momentum theory, what happens if atmospheric velocity is larger than outflow velocity?

I am currently reading up on aerodynamics, essentially the actuator disk concept and momentum theory as it is described in e.g. Basic Helicopter Aerodynamics by Seddon and Newman. There they assume ...
1
vote
0answers
17 views

Flow through a packed bed

I'm given a situation where a horizontal tube is filled with metal oxide particles and a reducing gas is passed through it. I'm given all the parameters of the system, including the maximum pressure ...
0
votes
0answers
22 views

Energy required to move air through 50x50x50 hanger at 25mph

I've been trying to calculate how much energy it would take (without losses) to continually move a 50x50x50 meter blob of air through a hanger of the same dimensions. I came up with 620 watts which is ...
1
vote
1answer
96 views

Can a thrown egg chip (or break) a car windshield?

Is it possible to throw an egg with such speed that a car windshield will chip (just like with stone chips?) I have searched around for existing research in the area and have found that the impact ...
0
votes
0answers
21 views

Tank draining with piston

I am trying to solve a problem which is close to the tank draining (as here Fuel tank draining) but with a piston a the top of the tank which means $p_A$ different of $p_B$. I search the velocity ...
0
votes
1answer
35 views

Flow rate of water in a gutter system [on hold]

I am attempting to build a waterfall out of a gutter system. I currently have an awning that is 72" by 48" with 3" high (tentatively) buffers on each side to keep the water from flowing off. The ...
0
votes
0answers
25 views

Fluid Mechanics Textbook Request [duplicate]

I'm looking for a textbook with which to independently study fluid mechanics. I have been searching a bit by myself, and my problem with what I have found so far is that the texts assumed certain ...
2
votes
1answer
39 views

Why do flat sheets of paper twist more than paper cones as they fall?

If I cut a 10cm circle out of a piece of paper and drop it, it will twist as it falls, even if it's rigid. If I then cut out a one-quarter wedge of the circle and tape the remaining three-quarters ...
2
votes
0answers
34 views

Are there resources for simulating and/or theoretically describing solitons?

Recently there are striking new ideas emerging on "lower level" dynamics with respect to quantum mechanics involving fluid mechanics principles, including hints of soliton-like aspects to particle ...
3
votes
3answers
82 views

Why do nuclear weapons create a blast wave?

As far as I know, in a nuclear explosion the energy is released in the form of radiation (neutrons, gamma rays, alpha particles and electrons), light and heat. There isn't a chemical reaction that ...
0
votes
0answers
14 views

Evolution of normal of material surface moving at a steady velocity

I need some help with the following question: A material surface moves with the fluid with a steady velocity $\mathbf{U_{o}}$. Show that the unit normal $\mathbf{n}$ to the surface evolves according ...
0
votes
1answer
60 views

Why oobleck does not obey Newtonian dynamics? [duplicate]

In the following post we can see that some guys are walking on Non-Newtonian fluids. As far as I know that, we can not predict the exact amount of strain if we predict some forces. therefore the curve ...
0
votes
1answer
25 views

Conventional definition of ideal fluid

According to Landau&Lifshitz, an ideal fluid is one with zero viscosity and a negligible thermal conductivity. This is also the FR.wikipedia version: En mécanique des fluides, un fluide est ...
1
vote
0answers
25 views

Solving inhomogeneous Stokes equation

I want to solve the Stokes inhomogeneous equation, i.e. $$\nabla^2 \vec v -\nabla P = \vec f(r,\theta)$$ $$\nabla\cdot\vec v=0$$ where $\vec f$ is irrotational, i.e. $\partial_y f_x - \partial_x ...
0
votes
1answer
29 views

Height dependancy when adding volume from below to a fluid column

Suppose there is a fluid column of height H and there is a screw already inserted from outside the column entering through the bottom of the column. The screw has a total length L and only 0.1*L is ...
3
votes
1answer
62 views

Russian propeller fluid dynamics [closed]

On a recently launched Russian Diesel-Electric Submarine, the rear Prop has two distinct features. You can see spheres at base of every propellor blade. Also, the trailing edge of the shaft has four ...
0
votes
1answer
19 views

What forces act on an object submerged in flowing fluid in an enclosed environment (i.e pipe)?

Let's say we have a pipe with water flowing through it and obstacle is inserted into the pipe and is rigidly fixed to the inner wall so that it does not get washed away. What forces are exerted by ...
2
votes
0answers
19 views

Limits for the linear wave equation

In acoustics and continuum mechanics the following wave equation (for Speed of Sound $c$) for the pressure field $p$ is well-known: $\partial_t \partial_t p = c^2 \Delta p$. This wave equation can be ...
2
votes
3answers
60 views

What is basically the difference between static pressure and dynamic pressure?

What is basically the difference between static pressure and dynamic pressure? While studying Bernoulli's theorem, I came before these terms. The law says: When the fluid flows through a small ...
0
votes
0answers
23 views

Density of an astrophysical ring of fluid around a star

*An equilibrium ring of isothermal fluid orbits a star at radius R. In the plane of the ring, mechanical equilibrium results from a balance of centrifugal force and the gravitational force of the ...
0
votes
0answers
22 views

Micro gripper for conveying tiny objects

Figure below shows a micro gripper used for conveying very small objects (i.e. the spherical object in Figure) and putting them in desired place using capillary force principal in a liquid bridge. To ...
2
votes
0answers
32 views

What is the essential concept behind the difference in the fundamental solutions of the Stokes and Poisson equations?

The fundamental solutions, i.e., the solution with a point source, of the Poisson's equation and the Stokes equations in 3D are: $$\nabla^2 f=\delta(\boldsymbol x) \ \Longrightarrow\ G(\boldsymbol ...
1
vote
1answer
45 views

Can I tell where a leak is in a vertical water pipe based on the water pressure at the bottom?

I have a buried water line with a leak in it and I want to locate approximately where it is. The line runs uphill to a storage tank. I've isolated the leak to one section of the pipe. The diameter of ...
0
votes
1answer
45 views

Decrease in system pressure do to gas dissolution?

A system of fixed volume contains two fluids as illustrated in the figure below, in equal volumes. Their pressures are both equal and high (much greater than atmospheric pressure). Initially the ...
2
votes
0answers
45 views

What happens to running water in sub-zero environment?

Many rivers in sub-zero winter temperatures don't freeze (photo). For simplicity let's discuss a (small) water pipe/canal with uniform cross section, inclined by an angle $\theta$. It seems that: ...
1
vote
0answers
23 views

How much energy to overcome surface tension and create air bubble at an air/water interface

here is my question. Hope you'll help me ;-) Consider a test-tube, almost completely filled with water, and closed with a stopper. Turn it over and then remove the stopper. If the diameter of the ...
0
votes
1answer
38 views

Can an air bubble in a liquid be faster than its terminal velocity

The title says it pretty much. I am wondering if an air bubble in a liquid can move faster (relative to the surrounding liquid) than its terminal velocity?
2
votes
0answers
34 views

Maximum hole size to stop a fluid passing through a solid

In a previous question, the following is answered in a general sense: Assume I have a inverse cone which holds 200ml water. I am going to cut the tip of the cone to create a small hole. How to ...
0
votes
0answers
12 views

Are centrifugal fans subject to triboelectric effects, and if so can the increase in charge be predicted and measured?

A centrifugal blower is a device that moves gas, usually under power of an electric motor. The blower housing and impeller may be metallic, but often are made of plastic materials. My question is ...
0
votes
1answer
55 views

Isn't Pascal's Law valid even if we DON'T ignore gravity?

Pascal's Law can be read anywhere online. Now suppose I want to apply on earth taking into account the variation of pressure with depth. So I don't want to ignore the effect of gravity. So I have ...
0
votes
1answer
35 views

Fluid dynamics? What will happen to liquid pressure and flow rate in a system that splits and recombines the the flow of liquid?

This question has to do with sending liquid coolant at a temperature of -25C thru standards computer water cooling components, like a CPU Waterblock, GPU Waterblock, and 120MM Liquid Radiator. I ...
4
votes
1answer
116 views

Integral of Sedov's self-similar solution to the spherical blast wave problem

I'm studying the Taylor-Sedov self-similar solution to the problem of a strong explosion in a homogenoeus atmosphere. The problem is discussed in Landau & Lifschitz VI (in the 2nd edition it's ...
0
votes
1answer
35 views

Strong and weak turbulence

As far as I understand, in general, turbulence describes the process of transfer of energy from a large scale, at which a system is perturbed, to a small scale, where dissipation happens. At ...
2
votes
0answers
67 views

What does the net force do with this droplet in magnetic field?

Consider a spherical droplet with radious $R_d$ which is coated with an immiscible ferrofluid with volume equal to $2v_f$ (shown dark in Fig. 1). While the droplet is in rest on a surface, if I ...
0
votes
1answer
14 views

How do we define capillary number in 2D (two dimensions)

In 3D the capillary number $Ca$ is defined as: $$Ca=\frac{\nu \rho U}{\gamma}$$ where $\nu$ is the kinematic viscosity ($m^2/s$), $U$ is the velocity ($m/s$)and $\gamma$ is the interfacial tension ...
1
vote
1answer
66 views

Application of Bernoulli's theorem

My teacher told me the following examples of Bernoulli's principle. I didn't understand how Bernoulli's principle is applied in these examples. It is dangerous to stand on edge of platform when ...
1
vote
3answers
52 views

How much of the energy of a car is required for overcoming air resistance?

How much of the energy of a car is required for overcoming air resistance? For example, assume a car going 65 mph has a mileage of 25 gpm. If all air resistance was eliminated, approximately what ...
0
votes
1answer
61 views

What causes surface tension actually? [duplicate]

Surface tension has really made me crazy! Surface tension occurs at the interface of air & water. It is a force per unit length tangential to the intersurface. But what actually causes it? One ...
2
votes
1answer
57 views

“Where” does dissipated enstrophy go?

We are all familiar with the kinetic energy dissipation and how it is converted into heat which can either be radiated away or go into the internal energy of the system. In the enstrophy transport ...
0
votes
4answers
51 views

What is the friction force at terminal velocity?

As terminal velocity is inversely proportional to viscosity or fluid friction, then my question is: at terminal velocity, the fluid friction is maximum or zero?
0
votes
1answer
45 views

Falling raindrop internal movements

A falling raindrop has the shape of a drop, because of the friction with the air it's falling through I wonder, does this friction also cause a circular internal movement in the drop like this? ...
0
votes
1answer
26 views

Dependence of streamlined flow on viscosity

My teacher told true class the following statement:- Streamlined flow is more likely for liquid with more viscosity as sturdy flow can only be achieved with slow speed. It's true that viscosity ...
0
votes
1answer
28 views

A fluid in a wide tube being centrifuged

Imagine a large, awkward and imbalanced centrifuge with the glass test tube in the shape of a large rectangular prism, rotating about one of its ends parallel to the sides. Inside this glass test ...
1
vote
0answers
31 views

Navier-Stokes equations through a orifice [closed]

I have reactor that looks as follows : In the first part, my reactants flow in. The reaction is started and generates heat as a result. It then expands slightly into the second part where after ...
1
vote
1answer
26 views

Prove thrust is double the dynamic pressure across a nozzle

I'm trying to teach myself some of the content from 'Rocket Propulsion Elements' by George P. Sutton. After reading over the first couple of chapters feeling like I understood everything, I came ...
1
vote
2answers
29 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 ...
0
votes
0answers
28 views

Lovely flow rate [duplicate]

How can we calculate the measure of the air flow rate when it is coming out of the balloon? (I mean that which parameter affects that? For example, the measure of balloons neck or the ratios or ...
6
votes
1answer
76 views

How can a droplet of liquid float on the surface of the same liquid?

This can happen during the rain, or when pouring water. Sometimes small (1-2 mm) droplets of water float on the surface for some time (a few seconds) before coalescing with the big body of water. A ...
1
vote
1answer
41 views

Flow rate through hole at bottom of tank, estimate time for depth to reach 1 foot

I am a structural engineering student and have limited experience in fluid dynamics. I'm not quite sure if I'm going about the problem in the correct way. The question is: An open cylinder of ...