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

learn more… | top users | synonyms (1)

0
votes
0answers
19 views

Heat system: Dynamic - quasi-stationary - static

I am an engineer in the field of district heating and in the future I will work together with people from computer science and physics. I have a question regarding dynamic/quasi-stationary and ...
10
votes
2answers
604 views

Energy from man-made tornadoes

Peter Thiel just paid $300,000 to Canadian inventor Louis Michaud who is working to construct useful "man-made tornadoes" or "atmospheric vortex engines" which could be components of future power ...
4
votes
1answer
34 views

Symmetry Arguments: Flow Through Cylinder

Why can for symmetry reasons a steady, viscous, incompressible flow, obaying the N.S equation: $$\rho(v \nabla)v = -\nabla p + \eta \Delta v $$ That flows through a cylindrical(very long) pipe not ...
2
votes
1answer
131 views

Current density in phase space

$\newcommand{\dd}{{\rm d}}$ I have a question which arises from looking at the impact free Boltzmann equation. Let $(\vec{x},\vec{v})$ be a vector in our phase space $\Gamma^N = \mathbb{R}^{6N}$. The ...
0
votes
0answers
40 views

Toricelli's law of efflux in moving container

Suppose there is a big tank of water with a small hole near the bottom. Now if this tank starts moving with say a velocity 'v', then will Toricelli's law hold? I tried directly applying Bernoulli's ...
6
votes
3answers
891 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 ...
3
votes
2answers
79 views

Pressure in a fluid

If a fluid is flowing along a vertical line with a constant velocity, will the pressure at every point be the same and irrespective of height?
1
vote
0answers
23 views

What is the impeller flow rate of a watercraft with the given information? [closed]

Given Information: Total craft mass: 100kg. Dimensions: 200cm x 60cm x 10cm thick. Water density 1,000kg/m3. Acceleration: 0 – 12m/s in 5s. Top speed: 12m/s Impeller diameter: 10cm. What is the ...
5
votes
1answer
41 views

How should I think of a liquid in terms of interatomic potential and molecular speed?

A rather simple question for liquids specialists I guess but I have hard time finding information about this. Here is my problem. I understand the ideal gas theory and the Maxwell's speed ...
2
votes
1answer
43 views

Question about propellers

A ship moves forwards because a rotating propeller sends water backwards. The diameter of the propeller is as large as possible because in order to be efficient it must push the the greatest feasible ...
1
vote
1answer
22 views

How are probe liquids selected for Surface Energy measurements?

Why are water, ethylene glycol and diiodomethane generally used for surface energy measurement?
0
votes
1answer
42 views

Conterflow heat exchanger with different flow rates

If we have tube in tube heat exchanger, in classic situation surface area in contact with both fluids is the same (if we ignore wall thickness of the tube). If fluids have significantly different ...
1
vote
4answers
55 views

What makes the magnitude of the force of friction velocity dependent in one scenario, but not the other?

When a solid objects makes contact with another solid object, I believe the magnitude of the force of friction between them does not depend on the relative speed of the two objects. When a solid and a ...
3
votes
2answers
547 views

Why does this capillary action generator not work?

So I was doing a bit of reading. Apparently the the obstacle to generating energy from the forces driving capillary action is breaking the surface tension at the top of a capillary tube. It is just ...
3
votes
1answer
2k views

Torque on a rotational cylinder in viscous fluid [closed]

I've been stuck on what I'm pretty sure is a simple part of a larger question. It's a cylinder (radius a) spinning in a viscous fluid. It's rotating at rate $\Omega$ .During this question we get that ...
7
votes
1answer
255 views

Why Are Normal Shock Waves Unstable in a Converging Channel?

While learning about shock waves in an introductory Gas Dynamics course, it was revealed that normal shocks are unstable if formed in a converging channel. Even if the local conditions ostensibly ...
3
votes
1answer
765 views

Perfect fluids in cosmology?

In cosmology, it is often assumed that the equation of state of a cosmological fluid is of the form $p=w\rho$. Why is this? Is it the equation of a perfect fluid? Why does $w=0$ for matter $1/3$ for ...
1
vote
0answers
25 views

How can frequency of waving in water change the direction object on the surface goes?

In an Australian experiment the physicists studied effects of a simple object that causes waves in fluid. They found that if it vibrates slow, the objects on the surface moves away from the vibration ...
0
votes
0answers
24 views

Equation of state for a radiation fluid

Can anyone give me (point me to a reference of) a derivation of the equation of state for a radiation fluid: pressure = energy/3 Much thanks.
0
votes
1answer
49 views

Terminal Velocity in Water

Another question concerning classical physics. On Earth, the combination of air resistance and gravity interact in a way that creates the phenomenon of terminal velocity. Do other fluids (for example, ...
0
votes
1answer
41 views

Physics behind blowing soap bubbles

Is it possible, using the surface tension of a soap bubble, to calculate the maximum pressure (created by the air flow) it can withstand while still attached to the orifice to prevent it from ...
0
votes
0answers
28 views

What makes some air bubbles in water more persistent?

In a plastic bottle of water, near the walls, it is common to observe the presence of little bubbles (I would estimate them to be $\approx0.5$mm in diameter. In my experience, most of these bubble ...
1
vote
1answer
105 views

Using water pressure as pushing force in a floating bath tub? [closed]

Does physics allow for water pressure to work in this way? if so What formula can prove this? (backup link 1, backup link 2)
1
vote
2answers
44 views

Why do bubbles group when one pops? [duplicate]

I was recently observing the way bubbles move as they pop and disappear. I noticed that when bubbles destabilize and pop, the remaining bubbles immediately surrounding it will move to fill its place. ...
1
vote
1answer
97 views

Rain system movements and highways?

In my free time I sometimes enjoy watching the weather or radar and trying to predict how a rain system will move. Pretty often I notice that a small rain system or even a large one will congregate or ...
1
vote
0answers
27 views

Gas diffusion through a flat plate boundary layer

Set-up Suppose we have a flat plate with a flow of gas parallel to the plate. The flow creates a boundary layer on the surface of the plate. Now, the gas is carrying a reactive species, which is ...
1
vote
1answer
52 views

Energy taken to move volume of blood through a blood vessel

I am trying to find simple ways to get rough answers to how much energy it would take for a unit volume of blood to move along a blood vessels. My main aim is to compare energies it would take for a ...
1
vote
1answer
37 views

Integral of a velocity profile?

Part of my fluid mechanics homework asks me to solve: $${\partial u\over \partial x} = 0$$ Which represents how the velocity profile, u, changes in the x. I'm not sure whether you can integrate ...
1
vote
0answers
20 views

About the fluid friction along the wall in pipes

I wonder how can the friction between the fluid and the wall in a cylinderical pipe can be calculated. Is there any theory that i can refer to? i also want to check if there's any relation between the ...
3
votes
0answers
26 views

How does air going through silica gel change its humidity

Assume that the properties(temperature,humidity,velocity and so on) of the incoming air flow stay constant. The air flow goes through a silica gel plate. Humidity of the air will decrease, but how to ...
3
votes
1answer
107 views

Mach no. should be constant for existence of similarity solution

I am reading some research papers on Taylor-Sedov type self-similar solution to the blast wave problems... It is written that for the existence of similarity solutions Mach number should be ...
1
vote
1answer
67 views

Fluid filled open container in space/vacuum

I have water in a bottle, as I open it in space(or vacuum for that case ). From what I have read in books the water will instantly vapourize,as the vapour pressure of the water inside, far exceeds the ...
1
vote
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 ...
1
vote
2answers
37 views

Does eq. of continuity hold in vacuum too?

When a streamlined flow of water flows down through an ordinary tap, it's cross-sectional area decreases according to eq. of continuity due to atmospheric pressure. If the same apparatus were to be ...
7
votes
6answers
700 views

Why do liquids separate in space with no gravity?

I've seen videos of people in space (on ISS) who squeeze a bottle or something and liquid comes out, it then separates into smaller balls. Why is this surely it should stay pretty much together ...
1
vote
0answers
20 views

Diesel injector sac pressure calculation [closed]

I am trying to calculate the nozzle sac pressure required to deliver 60mm3/ms of diesel fuel into a pressurised cylinder (19MPa). The nozzle has 5 delivery holes of diameter 0.157mm and the discharge ...
0
votes
1answer
31 views

Does water have shear thinning property? [closed]

I'm working on a project and I need to know if the water is viscoelastic? does water have shear thinning property?
1
vote
1answer
40 views

How the flow is distributed when the water flow from one river/drain to multiple rivers/drains?

Assuming that water ( total amount $Q$) flows down from one river/drain, into multiple rivers/drains, under the action of gravity, as shown below: How the flow ($Q$) will be divided among different ...
0
votes
1answer
78 views

Why does pressure decrease as velocity increases?

Bernoulli's principle states that as velocity increase pressure decreases. But higher the velocity, greater is the temperature and pressure must be high. Can you explain the situation in both the ...
0
votes
0answers
40 views

What is the filling time of this liquid storage tank?

A spherical storage tank ($R=3\:\mathrm{m}$, heated just enough to keep the sodium liquid) has to be filled from the lowest point with liquid sodium (at just above its melting point). A pump, very ...
0
votes
0answers
44 views

What is the difference between the pressure and “pressure force”?

I am in the process of going through a question pertaining to inviscid flow over a cylinder. The velocity field is, in polar co-ordinates: $$\vec{u} = U_{\infty}(1 - (\frac{a}{r})^2\cos2\theta,- ...
0
votes
0answers
16 views

What is the significance of the characteristic length in the Reynolds number formula? [duplicate]

It is said to be the diameter of the duct in closed flow cases, but what is its actual physical meaning in other types of flows, such as the flow over a flat plate?
0
votes
0answers
14 views

Should tunnel calibration factor be less than 1?

Regarding an experiment in which air is blown past a small-scale object (i.e. a cylinder) in a wind tunnel, should the tunnel calibration factor be less than 1? I couldn't find anything about this ...
1
vote
2answers
35 views

Why boundry molecules have more energy?

In a system of a solid or a liquid, why the molecules in interface have more energy compared to the bulk of solid or liquid?
1
vote
0answers
31 views

How do impurities affect the surface tension of fluids? [closed]

I want to know what happens to the surface tension of fluids if we add impurities and the reason behind it.
0
votes
2answers
108 views

How fast does the water have to go? [closed]

I have a pot of water. There is a one-way filter at the bottom right: How fast would the water have to be travelling to go into the tank via the one-way filter? Also, I would like to have some ...
0
votes
0answers
19 views

Can the flow of hydrogen in a fuel cell be modelled as adiabatic?

Okay, so right off the bat I'll admit I need this for a problem I'm working on. Not homework though, a project, as a matter of fact. I'm considering taking compressibility effects into account, but ...
0
votes
0answers
21 views

Hydraulic conductivity and flow rate

I have several sources that have the following equation relating the change of volume in a cell to the hydraulic conductivity (permeability coefficient) $L$ and pressure differential $\Delta P$: $$ ...
0
votes
1answer
43 views

Why we have a leak in the pipe if the fluid pressure is lower than the atmosphere

I've read in many books that if our flow pressure is lower than the atmospheric pressure then we'll have a leak in our pipe, but I already know that the flow is always from the high pressure point to ...
2
votes
1answer
69 views

Normal Modes for Standing Waves in 1-D Acoustic Ducts with Arbitrary (but real) Impedance Jumps

Let's say we have a 1-D duct, such as this: Where $Z_i \equiv \frac{P}{US}$ is the acoustic impedance, L is the length of the duct in question, and S is the area of the cross-section. In general, ...