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

learn more… | top users | synonyms (1)

2
votes
1answer
184 views

Velocity field induced by vortex points along ellipse

I'm investigating the velocity field induced by a continuous distribution of 2D vortex points distributed along an ellipse $\{a\cos\theta,b\sin\theta\}$. I'm interested in the field inside the ...
0
votes
1answer
99 views

Energy of liquid and gas at same pressure is different?

Air compresses (change in volume) and it creates pressure. It's the internal energy (momentum of each molecules) creates that pressure. But in liquids as it can't be compressed (may be by .3% if I am ...
3
votes
3answers
404 views

Water Level and Pipe Widths

I ran into a bit of physics yesterday, and couldn't understand the physics at work. I've been scouring the Internet, but haven't found the answer yet. I'm guessing there's a basic principle I'm ...
1
vote
0answers
130 views

Time required to fill a pipe line

This is quite embarrassing to ask, but I haven't done a fluid flow calculation in a very long time and when you don't use it, you lose it! I have a natural gas pipeline that I want to purge of air ...
1
vote
0answers
56 views

Closed pipe/sound resonance sound type sound coming from mineral processing plant

I work near a very large mineral processing plant which does vibrate our building and there is also a sound/feeling very similar to the closed pipe/sound resonance that is achieved when opening a back ...
3
votes
1answer
112 views

Calculating Length Scales from Passive Scalar Field

I have a set of PLIF images of a passive scalar advected in a turbulent flow. I'm wondering if it's possible to estimate the integral length-scale based on the images of the passive scalar, and if ...
0
votes
3answers
267 views

Fluid properties

I cannot understand the following sentence, Without flow , however, shearing stresses cannot exist, and compression stress or pressure is the only stress to be considered. (from A Physical ...
3
votes
1answer
171 views

Torque of a rotating fluid on a weighing scale

I was trying to do an experiment to measure torque (Moment force) of a rotating fluid. I placed a cylindrical vessel of dia-12cm with 1liter of water on a weighing scale and using a spoon I rotated ...
0
votes
0answers
35 views

Specific Gravity vs. Pore Space in Chromatography Column

Wondering if we can apply molecular specific gravity to elucidate average time required to pass through a column given porespace, distance and viscosity? This would eliminate the need for special ...
1
vote
1answer
255 views

Compressible flow - subsonic to supersonic and the 2nd law of thermodynamics

I'm reading chapter 16 in Fluid Mechanics by Kundu. It is stated (figures 16.16 and 16.17) that in a constant area duct flow with heating or friction, to go from subsonic conditions to supersonic ...
1
vote
1answer
3k views

Flow Rate and Orifice Diameter

I have a electrical/electronics background and have limited knowledge of Fluid Mechanics. So, i will try to be as clear as possible. I am currently working with brake fluid in an ABS system and to ...
2
votes
1answer
465 views

Momentum Equations for Micropolar Fluid

I am looking for the derivation of Momentum Equations for Micropolar Fluid $$\rho\frac{D\vec V}{Dt}=-\nabla p+(\mu+k_1^*)\nabla^2\vec V+k_1^*(\nabla\times\vec N^*)+\vec J\times\vec B ,\\ \rho ...
0
votes
1answer
306 views

Why whirlpool causes force towards its center?

Higher velocity implies low pressure. So in whirlpool the velocity of water have to decrease with radius in order to have force towards its center. My question is how is explained whirlpool formation ...
0
votes
0answers
49 views

Stagnation point from complex potential

I just wanted to see if I am doing this right. $$\Omega(z) = U(z+\frac{a^2}{z})$$ So to find the stagnation point: $$\Omega'(z) = U(1-\frac{a^2}{z^2})=0$$ Therefore stagnation points occur at: ...
5
votes
3answers
5k views

Reynolds number and inertial force

The Reynolds number is defined as the ratio of ´inertial´ forces to viscous forces. $$ Re = \frac{\text{Inertial Forces}}{\text{Viscous Forces}}$$ Now, viscous forces make sense to me. They are ...
3
votes
1answer
75 views

(Why) is a solid easier to suspend in a thick slurry than in a liquid?

When making cacao (the non-instant type), one usually mixes the powder with a small amount of milk or water before mixing this slurry into the rest of the milk/water. Some manufacturers of slurry ...
2
votes
1answer
68 views

Velocity from velocity potential

I have this homework question and I get a different answer to the solutions. In Cylindrical polar coordinates $(r,\theta,z)$, the velocity potential of a flow is given by: $$\phi = ...
2
votes
3answers
8k views

How to establish relation between flow rate and height of the water column of the tank?

Suppose a water tank has 1" diameter drain at the bottom and is filled with water up to one meter height above the drain. What time it will take the tank to drain out completely. Now say, the tank is ...
3
votes
1answer
234 views

Static pressure of free air stream

One of the common misunderstandings regarding Bernoulli's principle is that, in general, "faster moving air has lower pressure". Bernoulli's principle can only be applied to asingle streamline in ...
1
vote
1answer
142 views

Surface Water Drainage - Grate Inlet Capcity

The situation is a grated drain across a driveway entrance (so a thin long drain) if I know the roughness of the upstream surface (ie mannings roughness), the slope of the surface upstream (which is ...
2
votes
1answer
2k views

What is bulk viscosity and how does it affect the flow? [closed]

What is bulk viscosity and how does it affect the flow? Explain the idea of introducing such a term in the Navier-Stokes equation. What are the consequences if not taken into account?
1
vote
0answers
198 views

Projectile motion of the water surface from water discharging from a pipe

I am looking at pipe flow into a pit. How do I calculate the outside water surface path. I understand how to calculate projectile motion from calculus in terms of a velocity, point object and ...
4
votes
1answer
84 views

How to relate wingtips vortices with the energy loss it engenders?

On planes, wingtips vortices engender a loss in terms of lift, and an incresed of the drag, so an energy loss. Is there any possibilty to find a mathematical model relating both ? Thanks for the help. ...
2
votes
0answers
192 views

How does an atomizer work?

Will someone please explain how a basic pump atomizer works? I have a feeling it has something to do with pressure and the Venturi effect, but I'd really like to know precisely how they work as ...
0
votes
1answer
1k views

What are the assumptions of the Navier-Stokes equations?

I wanted to model a real life problem using the Navier-Stokes equations and was wondering what the assumptions made by the same are so that I could better relate my entities with a 'fluid' and make or ...
0
votes
0answers
88 views

What does “define analytically” mean?

I'm trying to do my homework in physics but here I have found something that I am not understanding. It says: Define analytically the terms that should stationary flow accomplish. I know that ...
1
vote
1answer
118 views

Visualisation of vortex flows

Are there examples of vortex flows (eg: von Karman vortex street or large eddies) which are visualized in a way apart from displaying where the mass is displayed? I can imagine there to be a display ...
3
votes
2answers
203 views

What is the theoretical justification for a fluid flow's being irrotational?

I am not a fluid dynamicist, and I really just began thinking about this problem as my curiousity drew me into building an answer for the question What really allows airplanes to fly?. It is very ...
0
votes
1answer
207 views

How to calculate the energy required to generate a vortex? [closed]

I am looking for the formula to calculate how much energy it requires to create a vortex. Can anyone assist please?
7
votes
1answer
570 views

How to make the bubbles in my soda drink last longer?

I would like to make the bubbles in my soda drink last longer. For example, one good thing to do is to keep the bottle shut when you don't drink. But what else I can do? Should I try to minimize the ...
1
vote
1answer
153 views

May I know how a vortex tube works? [duplicate]

From my point of view, high gas pressure input creates air rotation inside the tube. Due to the rotation, the kinetic energy in the air change to internal energy. The internal energy release as heat ...
0
votes
1answer
179 views

Derive conservation law using divergence theorem

Material scientists have discovered a new fluid property called "radost" that is carried along with a fluid as it moves from one place to the next (just like a fluid's mass or momentum). Let ...
0
votes
0answers
170 views

Waves produced by a mass of water on the calm sea surface

Suppose we have a parallelepiped shaped box full of water on the surface of the sea. Suddenly the box disappears. What is the shape of the waves vs. time caused by the fall of the water contained in ...
3
votes
2answers
207 views

What explains the effect of water's path falling around a ball/curve?

Disclaimer: I'm not a physicist. If you take an apple or a ball (or a cylinder works too) and put it under a tap such that the water falls down the side (not the centre) of the sphere, you get water ...
7
votes
1answer
282 views

Why is there a space between the flame and the nozzle on the space shuttle?

Why is there some space between the flame and the nozzle on the space shuttle? (see above picture)
3
votes
2answers
575 views

Example of inviscid flow with drag

This was my engineering viva question and I couldn't think of any example, for I am totally convinced that there cannot be drag in a inviscid flow. It also bothers me whether it is possible, a ...
3
votes
2answers
323 views

Water level difference by pumping [closed]

Open tank is partially filled with water and is divided into two equal parts by the wall. The wall has pipe that connects both sections. Obviously, water levels are equal from both sides (Fig.1). ...
17
votes
1answer
236 views

What are the equations of motion of a hole in a soap bubble?

Imagine the following situation: I have a thin stationary water film, like a soap bubble, suspended inside a large ring. I throw a small loop of string onto the film and punch a hole inside it. How ...
3
votes
1answer
92 views

Nonlinear waves and shock formation

In the cases of nonlinear acoustics, why is shock formation unlikely when the dispersion is strong when compared to the nonlinearity of the wave?
1
vote
1answer
276 views

Aerofoil Theory Project

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 ...
3
votes
1answer
126 views

Mysteries of the water meter

Recently, I got an exceptionally high bill for water consumption. I went to check my water meter, and saw that it rotates in a pace of about 200 cc per minute, even though all the faucets in my home ...
1
vote
1answer
193 views

Ship wake height

It is well known that a ship traveling in a deep water produces wake. Far from the aft of the ship, these wake are called a Kelvin wake. I found the mathematical expression of the shape of the wake, ...
4
votes
2answers
577 views

Finding Stagnation Points from the complex potential

I am trying to find the stagnation point of a fluid flow from a complex potential. The complex potential is given by $$\Omega(z) = Uz + \cfrac{m}{2\pi}\ln z.$$ From this I found the streamfunction to ...
0
votes
3answers
205 views

Does the ceiling fan make the air and dust spiral in?

Does the rotation of ceiling fan makes air circulate in a spiral, circular motion beneath the radius of fan or the air from outside is also mixed with it and replaces the air in room? A ...
3
votes
3answers
3k views

Why should fluids be confined for Pascal's Law to be applicable

When is Pascal's law about fluid pressure propagation applicable? Is it applicable to a closed circular pipe with a pump rotating the fluid, but not to a tub of water. Most statements require only ...
2
votes
1answer
66 views

A way to track a gas's expansion

I was wondering if there is a way to see, empirically, how a gas behaves. Perhaps the most natural way is to use fumes with color, but they quickly disperse, rendering partially useless. Are there ...
0
votes
1answer
45 views

Non-uniform field pressure on fluid

I have been studying fluid mechanics and currently I was trying to understand Euler's equation for fluid flow. For that purpose, I was following this webpage. My problem is in understanding Eq.(12). ...
0
votes
1answer
177 views

how to reduce pressure drop in a 5/16 ss tube

I have a fluid line which passes high density fluid at $60 \text{psi}$. At the end there is a valve. I have a $30 \text{psi}$ dynamic pressure drop in the line valve itself creates a back pressure of ...
3
votes
0answers
159 views

Bubble in a pipeline

I am just thinking about this phenomenon: We have a horizontal pipeline with a flowing liquid, which contains a small bubble of gas. How do the dimensions of this bubble change when it reaches a ...
2
votes
0answers
55 views

Realistic Ocean Shears

I was wondering if anyone could point me to published data on the vertical structure of strong ocean currents, such as the Gulf Stream. I am primarily interested in the mean current profile as a ...