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

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Distance traveled by a water jet

I helped my kid in a science fair project, where we punctured holes in a water bottle at various heights and then measured the distance traveled by the water jets before they hit the ground. The ...
3
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2answers
143 views

Rayleigh-Taylor Instability dependence on acceleration direction

I'm trying to bolster my understanding of the Rayleigh-Taylor instability, and I've gotten stuck on the point of which fluid (more or less dense) is being accelerated into the other. Cases of uniform ...
3
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1answer
124 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 ...
4
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1answer
37 views

Does the definition of compressibility depend on the frame of reference?

According to many authors, a fluid is defined to be incompressible if the material derivative of the density $\frac{D\rho}{Dt}$ is zero, that is to say, that in an frame of reference following the ...
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0answers
14 views

water pressure relationship to volume [on hold]

I have a one inch pipe 120 feet long and caped. I have a 60 pound input of pressure. I put a half inch pipe at the end and open it. What happens to the pressure in the one inch pipe? If I add another ...
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1answer
6k views

Calculation of pressure from flow rate of water

Anybody kindly help me to find how to calculate pressure in bar from flow rate. I have a pipe and from that I am transferring water at a constant flow rate of 5ml/min. At this flow rate, with a 0.5 cm ...
11
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2answers
729 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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0answers
16 views

frequencies that affect newtonian and non newtonian liquids [on hold]

I have a science fair coming up and i need to know which sound frequences affect liquids, both newtonian and non newtownian. i also need to know the science and formulae behind it. Your answers will ...
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1answer
20 views

Monoatomic fluids and free space around atoms

In monoatomic fluids the atoms can move quite freely around each other. Is there any thermodynamic/statistical mechanic equation how much free space there is between the atoms? This has to be ...
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4answers
103 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?
3
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1answer
155 views

Fluid dynamics tsunami

I have been given a energy head (pressure) in meters for a given tsunami on land. If the tsunami hits a wall 1 meter by 1 meter, is it possible to calculate the height it will reach. I am thinking it ...
7
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0answers
106 views

Could Navier-Stokes equation be derived directly from Boltzmann equation?

I know how to derive Navier-Stokes equations from Boltzmann equation in case where bulk and viscosity coefficients are set to zero. I need only multiply it on momentum and to integrate it over ...
3
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1answer
177 views
+100

Fluid flow: Force acting on the fluid and the Navier-Stokes equation

Consider a one dimensional fluid flow in a rectangular tube. Typical streams are the poiseuille streams. Consider the case in wich we apply a force on the fluid. The Navier-Stokes equation (for ...
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2answers
72 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 ...
41
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5answers
14k views

How effective is speeding?

At a simple level, speeding in a car attempts to minimize the time required to travel a distance by utilizing the basic relationship: $$d=st$$ So for a given distance, time should be inversely ...
2
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1answer
16 views

Boat Hull Drag in Shallow Water

I paddle several different types of small craft in the ocean and bays near my home. One phenomenon I've observed is beyond my understanding of drag on a narrow displacement hull. When paddling in ...
5
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1answer
157 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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2answers
37 views

Do rotating non-circular projectiles also experience Magnus lift?

The Magnus effect has been studied on spherical projectiles such as golf balls, tennis balls, and soccer balls. The backspin of a golf ball leads to Magnus lift that opposes gravity, thus allowing the ...
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2answers
721 views

Difference resultant aerodynamics force on an airfoil and a flat plate

From basic airfoil theory the following free body diagram can be determined for a two dimensional asymmetric airfoil: Here the direction of the resultant force is governed by the geometry of the ...
2
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1answer
477 views

Force required to move a fluid out of piston at depth

I have a cylinder filled with water in it at the bottom of the ocean. Say 100 meters down. In this cylinder is a piston that moves up and down. Its job is to squish the water out the bottom of the ...
3
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1answer
67 views

Is Archimedes' principle valid with moving objects?

I was solving a classic application of Archimedes' principle: a body partially submerged that is made to oscillate vertically and perform a simple harmonic oscillations. The equations turn out to be ...
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1answer
74 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?
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1answer
38 views

Velocity field of solid body rotation [on hold]

Consider a fluid in solid body roation about the z-axis with angular speed $\varOmega$ Derive an expression for the velocity field (u(x,y), v(x,y)) and show the vorticity of this velocity ...
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0answers
38 views
6
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1answer
2k views

Is there an analytical solution for fluid flow in a square duct?

I couldn't find one but assumed it must exist. Tried to find it on the back of an envelope, but got to an ugly differential equation I can't solve. I'm assuming a square duct of infinite length, ...
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0answers
16 views

Reference for passive scalar

I would like to learn about turbulence of a scalar advected by a random velocity field. I know that this problem can be solved analytically and that the statistics of the scalar field are ...
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2answers
44 views

What is the pressure of falling water?

Imagine a breaking wave 10m high. The wave breaks onto a beach. What is the maximum pressure created by the wave on the beach, ignoring effects such as might be cause by air?
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1answer
214 views

Capillary action meniscus height in a tube fitted inside another tube?

I was thinking about how would capillary action change in a tube (classic example) and in a tube fitted inside another tube (considering water as the liquid involved). Height of liquid column: ...
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1answer
36 views

How can I add a rounded trailing edge to an airfoil? [closed]

I have an airfoil coordinates file (NACA 65(4)-421) with a sharp TE. I need it to be rounded. It doesn't seem that there are any tools available to help with this, so I've tried making my own Python ...
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0answers
28 views

Wind blows to surface, how long legs I need? [closed]

Wind blows onto the surface normally at at speed of 20m/s. The frame (in vertical plane) has two supporting bars in the plane of the ground as shown welded rigidly. What is the length of horizontal ...
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1answer
66 views

What is the physical origin of acoustic modes in a duct?

Lets deal with wave propagation in a cylindrical duct. We ask the question: "what is the general form of a pressure wave which can propagate through the duct?" In answering this, we assume that the ...
3
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1answer
35 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 ...
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0answers
12 views

the different settling speed of two solid particles in fluid

In a container full of fluid A, which can be water or oil, I have two solid particles, both of which are of the same material. These two particles are of different size. One is bigger than the other ...
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2answers
78 views

Ice when melted at zero gravity [closed]

I wish to know the behavior of ice at zero gravity, how ice will behave when melted at g=0? Thanks
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3answers
5k views

Is this really a golden ratio spiral?

In this blog post, I found this picture: There are other similar photos: and Does the water really form golden ratio spiral in such cases? Or is the photo just a provocative example, without ...
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0answers
15 views

Find parameters of blood constitutive equation [on hold]

I used a viscosimeter to study the rheology of blood. I have data of viscosity, speed, shear stress and shear rate. I want to find the parameters of the constitutive equation of blood: , where ...
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2answers
30 views

How to increase flow rate? [closed]

I am coming up with ideas of how to increase grain (corn, soybeans etc,) flow in a tube. My first idea is to have spiral ribs inside of the tube to create a vortex effect that will allow the grain to ...
9
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2answers
130 views

Why pouring milk from a height makes a chain shape?

I have noticed a chain-like shape when milk is poured from a height into a cup. Actually the chain pattern repeats itself after some distance and again till it reaches the milk in the cup. Any ...
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0answers
45 views

Establish a relation between height of the water column and time in a spherical container with a hole in the bottom [closed]

Suppose we have half of a sphere of radius $R$ filled with water. In the bottom of the container there is a hole of area $S_0$. Velocity of the water flow out of the hole is $$V=\lambda(2gh)^{1/2}.$$ ...
8
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2answers
248 views

Fluid Mechanics with calculus on manifolds

Fluid Mechanics is a branch of physics that uses a lot of vector calculus in $\mathbb{R}^3$ to describe phenomena mathematically. Calculus on manifolds, however, is the straightforward generalization ...
7
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1answer
160 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 ...
2
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1answer
28 views

Patterns in laminar flow of tap water

This is a simple experiment that anyone can do at home. Open your tap so that the water maintains a laminar flow, and the cross section of flow is considerably thin. Place your finger 3-4 cm below the ...
8
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1answer
340 views

Lagrangian Coordinates in Fluid Flow

I apologize if this is not the right place to ask this question: I am currently reading a paper by Y. Brenier, where for the fluid flow he introduces a Lagrangian label $a$ instead of the vertical ...
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1answer
197 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 ...
9
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3answers
272 views

Physics of how the cochlea isolates frequencies along its length?

Can anyone explain the separation of frequencies along the basilar membrane of the cochlea please? (equations would be nice) I understand it being related to the resistance caused by fluid in the ...
1
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1answer
103 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 ...
2
votes
2answers
105 views

What's the physics origin and meaning of $\delta_{ij}-k_ik_j/k^2$

The projection tensor $P_{ij}\equiv\delta_{ij}-k_ik_j/k^2$ happens frequently in fluid mechanics or field theory. What's the physics origin of this structure and what's the meaning?
6
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3answers
362 views

Why does the lake surface appear darker in some areas?

My question: What causes the surface of the lake to appear darker in some places? My take on the matter: Firstly, I don't dare to say it's fishe which cause it. Secondly, the dark surfaces move ...
2
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4answers
2k views

What is the principle behind centrifugation?

What is the principle behind centrifugation? I understand the idea that you spin something around the centripetal force will cause an apparent force on the spinning system. However I don't quite ...
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0answers
20 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 ...