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

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187 views

Speed of sound in non-newtonian fluids

Recently I saw some videos of non-newtonian (shear-thickening) fluids like corn starch mixed with water(sometimes known as oobleck), where the fluid is placed on top of a speaker cone and starts to ...
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35 views

Which laws of physics apply when creating a soap blaster with pressurized air?

I want to create a soap blaster using: a 1" hose with 8 bar compressed air a non pressured container of soap and water mix without the use a pressurized tank I.e. something like this sand blaster: ...
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3answers
86 views

Can a very thin sheet of any material float inside a liquid?

When a body is immersed in a liquid,buoyancy is the net force of all the forces acting on it. Now the forces are equivalent to those which will act on the same volume of liquid.Rightly so,but ...
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295 views

Is it possible to extract nitrogen from the air via a centrifuge

I was thinking about how they have cans of compressed nitrogen for filling paint cans, and also that they sometimes will blow nitrogen in to food containers before sealing them, and that got me ...
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148 views

Velocity of a viscous fluid through a tube

When a viscous liquid flows through a tube in a laminar flow, why is its velocity highest at the center? I understand the concept of shear viscosity and why the liquid in contact with moving plate ...
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45 views

Variance and Intermittency in turbulence

In the turbulent transport of a scalar field, $\Phi$, decomposed into mean and fluctuating components, $\Phi=\left<\Phi\right>+\phi^\prime$, the scalar variance is defined as ...
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1answer
97 views

How can I predict the convective updraft speed above a stove element?

I want to know the rate at which air will ascend above a stove element. Is there some relationship between ambient air temperature, element temperature, and speed of the resulting updraft? If ...
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1answer
141 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 ...
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1answer
92 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 ...
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335 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 ...
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96 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 ...
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53 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 ...
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99 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 ...
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196 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 ...
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1answer
157 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 ...
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22 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 ...
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200 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 ...
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1answer
2k 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 ...
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1answer
343 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 ...
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228 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 ...
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45 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: ...
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3answers
2k 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 ...
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66 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 ...
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22 views

The definition (or perhaps, explaination) of Effective Pressure or Effectiveness in a Hydraulic System

I am trying to understand the effect of effective pressure or effectiveness in a hydraulic system. I have seen different units for effective pressure or effectiveness - e.g. Nm/Bar Nm/L etc. and I am ...
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1answer
62 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 = ...
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3answers
5k 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 ...
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157 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 ...
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111 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 ...
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1answer
1k 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?
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147 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 ...
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79 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. ...
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155 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 ...
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775 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 ...
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83 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 ...
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109 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 ...
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172 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 ...
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150 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?
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1answer
478 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 ...
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1answer
132 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 ...
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142 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 ...
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103 views

Pressure Rise in Closed Tank with 2 Inputs

Supposing you had a cylindrical closed tank inside the body of a submarine; the top of the tank is at 200m depth. The tank has height 2.5m and internal volume 1.8m^3. A section of pipework is ...
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142 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 ...
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2answers
191 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 ...
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263 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)
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445 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 ...
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2answers
286 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). ...
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1answer
195 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 ...
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46 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?
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195 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 ...
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113 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 ...