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

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Does gravity affect water permeability?

Suppose I have an approximately rectangular prism composed entirely of folded paper. If I place 600lbs on top of these rectangular sheets of paper, the paper should compress. How does this affect ...
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614 views

Calculating Reynolds number for a viscous droplet

I'm trying to develop a very basic scaling law/unit analysis for viscous droplet formation, and I'd like to get some rough numerical values of the Reynolds number to play with. To be specific, I'm ...
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3k views

Why do some carbonated drinks fizz more than others?

Wired magazine ran an article this month on carbonation in soft drinks. If all soft drinks are manufactured effectively identically, why do some types fizz more than others? For example, root beer ...
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32 views

Viscosity and Flow

I have a system with a fairly viscous fluid, 70,000 cP. The flow is induced by applying pressure to a plunger via compressed air. The error in viscosity for this material is +- 15% which can be ...
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7 views

Argument for stability of journal bearing via inertial and viscous forces?

As I understand a journal bearing, a rotor is levitated by hydraulic forces from the lubricant. While these are lots of studies on this subject, I can't manage to find a paper that coherently breaks ...
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Emptying a bottle faster by swirl

A moment ago, I was emptying bottles filled with water (2 liters) that are on the terrace of my house. As I did so I remembered something I saw on TV a some time ago (I don't remember when or where or ...
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41 views

Where can I get fluidics components?

Many years ago people were interested in developing fluidic circuits, i.e. circuits that are analogous to electric ones but that use fluids rather than electricity. It used to be possible to buy ...
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34 views

height of dam to allow certain flow rate

You observe water at rest behind an irrigation dam. The water is 1.5m above the bottom of a gate that, when lifted, allows water to flow under the gate. Determine the height h from the bottom of the ...
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13 views

Conservation Equations forming a Determinate Set

I was reading "molecular gas dynamics" by Bird and came across the the statement that For conservation equations to form a determinate set shear stress and heat flux must be expressed in terms of ...
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151 views

Feynman's derivation of Bernoulli (part of it)

OK, so what's up with the $\Delta M$ here? I don't get it. In fact, my textbook doesn't even put it in. I don't think it is a type-o because he continues on with the explanation. If anything I got ...
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327 views

Finding Surface Tension of water at certain Temperature and Pressure

So the question is: Using the Young-Laplace Equation (if applicable), find the surface tension (dynes/cm) for water at 20 degrees Celsius with 2.5 psi. Round to the nearest tenth. ...
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17 views

Would a solid inside of a parcel moving due to buoyancy be affected by Bernoulli's Principle?

If a parcel (or column) of hot air were rising due to buoyancy and an extremely light solid were to be inside of this parcel (rising with it), would Bernoulli's effect cause the solid to stay inside ...
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50 views

Pressure Question

I have a question that relates to an arrangement of natural gas pipelines but for simplicity I will be describing a less complex problem. Imagine that I have two large pressure vessels connected by a ...
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2answers
77 views

Bubbles of Different Size

Suppose that I have 2 bubbles of different sizes located in a liquid, and assume that both of those bubbles are close to one another. What exactly will happen to both of those bubbles? From a ...
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1answer
102 views

Liquid Column “Recoils” in a Sealed Cylinder When Hit by a Piston — Is it Possible?

Consider a cylinder filled partially with a liquid (e.g. water). The cylinder is sealed, and is at held at room temperature (e.g 298K). At equilibrium (or when no external disturbance is imparted to ...
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1answer
34 views

Do de Laval nozzles have to be asymmetric?

All pictures of de Laval nozzles I've seen have an hourglass shape where the convergent section is shorter than the divergent section. Is this necessary to attain supersonic exhaust velocities, or ...
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1answer
142 views

Sound Propagation using Finite-Difference Time-Domain (FDTD) considering wind effects

I am trying to plot the propagation of sound from a fixed source in a 2D environment using Finite-Difference Time-Domain (FDTD) Method taking into account the effects of the wind velocity. I came ...
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26 views

Books on experimental methods, fluid mechanics related

I need some good books on experimental methods, requirements are: Fluid mechanics related; Thermal, multi-phase etc. topics should be covered; Traditional methods are good, but it would be greater ...
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1answer
40 views

I would like to know what variables to consider when I experiment with pouring from bottles and the “glug” effect?

I am a middle school science teacher and want to model a science fair project for my students. Specifically I want to investigate using a vent in the top of the handle of a gallon milk jug to ...
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20 views

Bernoulli and ideal flows

The question states that there is a permanent source of liquid at the bottom of a given reservoir and I need to find the maximum elevation of the liquid surface given two cases: $1.$ a straight narrow ...
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1answer
25 views

Enstrophy and energy spectral density of vorticity

I'm processing some flow field data obtained by PIV for a turbulent jet with the intention of using the energy spectral density (ESD) function to say something about the processes going on. I'm ...
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1answer
128 views

Taylor expansion in Lattice Boltzmann Method derivation

Currently I'm trying to understand Lattice Boltzmann Method for solving CFD problems. In its derivation BGK approximation is used to get rid of complicated collision integral. But when they come to ...
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1answer
51 views

Does angular momentum of our planetary spin explain the natural 'log e' explanation (the spiral pattern) of my fossil gastropod collection? [closed]

If so, where is the momentum conserved? Any shell may shatter if from a recent land or sea shell. Is a fossil the same way, just waiting for decompression?
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1answer
57 views

Orientation of large water drops break-up

I have observed that if you pour small globs of water from a considerable height (let's say more than 20 meters), the globs will break up. This is not surprising at all since the amount of water ...
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3answers
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What is the physical meaning of diffusion coefficient?

In Fick's first law, the diffusion coefficient is velocity, but I do not understand the two-dimensional concept of this velocity. Imagine that solutes are diffusing from one side of a tube to another ...
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298 views

Why does your car lurch toward an oncoming truck as it passes you?

I notice that the larger the truck the greater the magnitude of the lurch. Can anyone give a physical explanation to this?
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4answers
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Define Pressure at A point. Why is it a Scalar?

I have a final exam tomorrow for fluid mechanics and I was just looking over the practice exam questions. They do not provide solutions. But pretty much I have to define pressure at a point and also ...
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32 views

Sum of velocity fields

In hydrodynamics the for a non-viscous flow the velocity (and density) fields are given by the continuity and Euler equations: $$\rho\frac{\partial \vec{v}}{\partial ...
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1answer
51 views

Is the viscous sublayer size universal?

We know the non-dimensionalized distance of the viscous sub-layer is 5 wall units for a turbulent boundary layer. It is common to see this in Fluid Mechanics books but seems somewhat arbitrary. I ...
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1answer
37 views

Must flow be supersonic for disturbances not to affect upstream?

I'm studying oil production and found a fact that puzzled me. It states that fluid flow downstream of the wellhead must be supercritical in order not to disturb the flow upstream of it. From ...
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1answer
136 views

How to calculate fluid(oil / hydrocarbon) loss under pressure

I'm trying to calculate the amount of fluid that would flow through an area dependant on the amount of pressure that there is. I'd also like to know the rate at which it would flow. Essentially I ...
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1answer
59 views

Vorticity versus Viscosity

For a work project I need to revive my aerodynamics knowledge again. Can somebody help me with the distinction between vorticity and viscosity. If a flow vorticity is not equal to zero, the flow is ...
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0answers
47 views

References on De Broglie-Bohm pilot wave theory

Are there any good books related to the not much popular De Broglie-Bohm pilot wave theory and its application in hydrodynamics, walking droplets concepts?
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2answers
42 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 ...
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1answer
47 views

Fluid flow through an orifice

Forgive me for my ignorance. What would be the method to determine the pressure a non compressible fluid creates when forced though an orifice? Keep in mind this orifice does not have a constant ...
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58 views

Position based dynamics constraint scaling factor

Reading through Müller et al., Position Based Dynamics, 2007 I got lost when passing from equation (5) $$\Delta p = \frac{C(p)}{|\nabla_pC(p)|^2}\nabla_pC(p)$$ to equation (6) (and applying the ...
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2answers
47 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 ...
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31 views

Home experiment with airfoils and Reynold's number

I want to do an experiment about lowering the Reynolds number of an airfoil moving through air. I want to figure out how to lower the turbulence around an airfoil. So my two hypotheses to lower the ...
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2answers
54 views

How can we show that pressure is exerted sideways too?

We can show that pressure upward and downward in a fluid is caused by weight of fluid column or volume. A simple derivation of this: ...
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1answer
173 views

Sum of forces with liquid in rotation

It's not homework (I'm teacher). I would like to compute sum of forces on this study : The shape is symmetrical like that I'm sure the center of gravity is in the center of the shape. I compute ...
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3answers
228 views

Bernoulli's principle on a curve ball

I've seen a few excellent answers here on the Magnus force, which explains why balls with a spin will curve. However, my intuition is still telling me that the Bernoulli's principle would push it the ...
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1answer
37 views

Why are lubicants like grease or oil slippery?

I know that grease or oil are slippery in nature but never thought of why? I want to know what causes this tendency.
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2answers
51 views

How come milk pours smoothly from a bag?

I have seen the commercial about the new beer can where it is vented by puncturing a whole on the can (air behind water). If you just pour normally with normal cans it will get bottle necked and the ...
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1answer
386 views

thought experiment involving water pressure

If I were to move the syringe up, and cause it to be stationary, how does that effect the pressure at the bottom of the pipe? How does the movement of this water effect the system setup and ...
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11 views

Kármán Line Definition from “Aeronautical Flight” (Mass, Area, and Lift)

This question asks something very similar, and the single following answer says, in part, that the balance is achieved when: $$ \frac{2m}{\rho(r) A C_L r} = 1 $$ [...] I note that the mass ...
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22 views

Maximum velocity in a viscous fluid

Situation: A viscous fluid is flowing through a tube, and the rate of ejection is x $m^3s^{-1}$ Finding the velocity of the ejected fluid would be simple enough, by dividing the rate of ejection by ...
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1answer
80 views

Reference Request: Fluid dynamics/Elasticity via Lagrangians

Would there be a book that does what Landau does in Fluid Mechanics and Theory of Elasticity using Lagrangian's/Action-principles, analogous to the presentation in Landau's mechanics? I have only ...
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1answer
41 views

How does one figure out how fast water is moving through a water intake on a dam?

Say the dam is Hoover dam for example. The intake is where the water flows in to turn the turbines that generate electricity. I want to know if there is an equation that describes the speed of the ...
3
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2answers
57 views

Viscosity and surface tension

Both viscosity and surface tension are dependent on the intermolecular forces between the molecules of the liquid. Supposing from this, shouldn't there be a directly proportional relationship between ...
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1answer
16 views

What concepts/rules apply for multi-stage pumping of water

For single stage (ie one pump) water transfers calculations for pressure loss are commonly done by adding the elevation difference of the start and end of the pipe line to the friction losses that ...