Questions tagged [turbulence]

A regime of nonlinear viscous flow characterized by random, rotational motion with a wide range of length scales. Its study is critical to many fields, such as aerospace, atmospheric science, chemical engineering, and astrophysics.

Filter by
Sorted by
Tagged with
0
votes
2answers
41 views

Reynolds number determines turbulent or laminar but Moody Chart has different interpretation

One can calculate the Reynolds number to determine whether or not flow is turbulent or not inside a pipe with circulating water. The formula is: $Re = \frac{\rho VD}{\mu}$ Let's say one gets $Re = 10,...
0
votes
1answer
22 views

Why does turbulent mixing result in a reduction of pressure and an increase in temperature?

For example, if i have a horizontal orifice plate in a tube and i'm pushing flow through it, there will be significant turbulent mixing downstream of the orifice plate. E.g. https://www.youtube.com/...
0
votes
0answers
5 views

What does near field shear layer mean?

I'm reading a research paper and the abstract is as follows... Ignition initiation by a turbulent hot jet involves complex transport and chemical processes with disparate and sensitive time scales. ...
1
vote
0answers
16 views

Some question regarding turbulent eddies

There's several concepts I don't have a clear understanding of: Plots of the turbulent energy cascade have a wave frequency as the axis - yet I see definitions of this "frequency" as the ...
1
vote
1answer
16 views

Turbulent Energy Cascade - Scale Between the Integral and Kolmogorov Microscale

I have seen derivations of the the length scale, time scale and characteristic velocity of eddies in the inertial or large-scale range and in the diffusive or Kolmogorov scale range. I'm interested ...
1
vote
0answers
27 views

How does water move out of the way/around an object moving under water?

Let's say a torpedo moved under the water. Water is virtually in-compressible right? So what happens to the water in front of the torpedo as it pushes forward? It has to somehow move out of the way, ...
-1
votes
2answers
41 views

What is the structure on SUV's top back edge? [closed]

I see a lot of SUV's that has the structure as shown in the picture .I am talking about the the top back edge (right above the back window). Wont't it worsen the streamlined design and causing more ...
0
votes
1answer
18 views

What is the function for the magnitude of air resistance/drag?

In John Taylor's Classical Mechanics, he gives a basic treatment on air resistance/drag. In order to do this, he models air resistance as $\mathbf{f}=-f(v)\mathbf{\hat{v}}$, and then Taylor expands $f(...
1
vote
1answer
64 views

Why friction losses depend on velocity squared?

This is the reason that suction pipes of centrifugal pumps are most of the times much wider than the discharge pipes and that restriction of blood flow in arteries is always an alarming event. Does ...
1
vote
4answers
28 views

Confused about the direction of the Magnus effect force

From what I've read, the cause for the force acting as the result of the Magnus effect is the formation of a bended wake behind the moving sphere. Take a look at that picture: From that picture, it ...
3
votes
2answers
722 views

Can a theory of everything solve the oldest problem of turbulence? [closed]

Can a theory of everything solve the oldest problem of turbulence? Can we have unified theory of universe without solving the problem of turbulence?
1
vote
2answers
53 views

Is theoretically possible to have the laminar flow above $Re=10^7$?

The onset of turbulent flow ranges greatly, for pipe flow I came across the information that the onset of turbulent flow occurs at approximately $Re=10^4$, while for boundary layers on the airplane's ...
0
votes
0answers
17 views

How to simulate salinity gradient in experiment?

I feel like the question is probably fairly fundamental. I have to recreate oceanic turbulence in terms of salinity and temperature gradients. Temperature is easy - heater. What should I do with the ...
0
votes
1answer
18 views

Energy cascade in turbulence

I have studied that energy is transferred from larger eddy to smaller eddy and so on until that energy is converted into heat via viscous dissipation. 1. What i am not able to understand is why is ...
3
votes
1answer
32 views

Why turbulence is non-equilibrium?

I've encountered this notion many times that turbulence is non-equilibrium (e.g., Falkovich & Sreenivasan, Physics Today, 59, 2006). However, I am confused about what does it mean by "non-...
-1
votes
1answer
46 views

Why does a running fan causes some soundproofing in the room?

I notice that when I switch on my fan inside my room, the room becomes soundproof to a great extent to the outside noises. The greater is the speed of the fan, the greater is the soundproofing. When ...
0
votes
0answers
19 views

Approximation of air resistance of rectangle with angle alpha

my problem is not that hard to explain, but maybe hard to model, because I couldnt find anything appropriate on the forum or internet..;D I need approximate the air resistance force of a rectangle ...
0
votes
0answers
17 views

Correlation function definition in hear transfer (statistical theory of turbulence)

I am trying to reproduce the approach in the paper by Nikishov. Since the paper is not easy to get I will just write out the statements here. They write the heat transfer equation for averaged ...
3
votes
0answers
72 views

From Kolmogorov (1941) to $k^{-5/3}$

I'm actually studying the famous paper of Kolmogorov (1941). I am trying to derive the passages that deduces the fact that the Energy spectrum has a dependency $k^{-5/3}$. As far as I know, the ...
0
votes
1answer
35 views

frequency wavenumber

Usually, when you have to go from frequency to wavenumber you have to adopt the following equation: $$k = \frac{2\pi f}{U}$$ where k is the wavenumber, f is the frequency and U is the velocity. ...
1
vote
1answer
55 views

Difference between alfven waves and magnetic fluctuations in solar corona

I have read in this paper https://arxiv.org/pdf/1911.07973.pdf about particles being accelerated in the solar corona either by Alfven waves (to my understanding when the turbulence is weak) or by ...
0
votes
0answers
27 views

How do we determine the flow regime during condensation without knowing the Reynolds number?

Condensation occurs in the mixed flow regime of a condensate film on a flat vertical plate. How does one determine the flow regime during condensation without knowing the Reynolds number? I know that ...
1
vote
1answer
32 views

Are the boundary and initial conditions only effecting parameters make turbulence unpredictable?

The book that I used to study turbulence states that "in a laboratory experiment initial and boundary conditions can not be fully under control, despite all the effort there will be infinitesimal ...
3
votes
1answer
36 views

Why traditional turbulence theory concerns so much about statistics such as correlations?

I have been wondering why the traditional turbulence theory, e.g., Kolmogorov's 1941 theory, concerns so much about things like two-point correlations, structure functions, their scalings, and so ...
0
votes
0answers
31 views

Modification of Mixing Length Damping Function to include Surface Roughness

Surface roughness has been incorporated into the van Driest damping function in studies by van Driest himself (1956) and more recently by Krogstad (1991) and Crimaldi et al (2006). These models ...
1
vote
0answers
51 views

Turbulence and the symmetries of Navier-Stokes

I am reading the book "Turbulence - The Legacy of A.N. Kolmogorov" by Frisch. He begins the book by introducing the different stages of fluid motion when the Reynolds number increases. In particular ...
0
votes
0answers
20 views

Behavior of parachutes in Crew Dragon launch escape experiment

When watching deployment of parachutes in SpaceX Crew Dragon Escape experiment, I noticed that sometimes parachutes collides with each other and later- separates. (Btw, you can watch this movie here, ...
1
vote
0answers
63 views

Reynolds number in General Relativity

Does the relativistic counterpart of the Reynolds number exist, and how can find it? And what is the dissipative term in Einstein equations?
1
vote
0answers
49 views

Good resource for Drag Coefficient vs Reynolds number (various shapes)?

The Wikipedia page on Drag Coefficient has a nice chart a little way down that shows the Drag Coefficient vs Reynolds number for a sphere, derived from experimental data. I am interested in looking at ...
0
votes
2answers
80 views

Physical interpretation of “Reynolds speed”

Reynolds number is the ratio of the fluid speed to some characteristic speed, $v_R = \frac{\mu}{\rho L}$ where $L$ is some characteristic length scale of the situation. Is there an intuitive ...
3
votes
2answers
151 views

Is there anything more chaotic than fluid turbulence?

Fluid turbulence is a highly complex and non-linear chaotic phenomenon. Great difficulties and complications are encountered when trying to accurately and robustly calculate or simulate fluid flows, ...
0
votes
1answer
49 views

Boiling water quites down [duplicate]

When I heat water in my electric kettle the noisy turbulence gets louder and louder as the water nears boiling. Shortly before the kettle turns itself off (presumably when it detects the temperature ...
1
vote
1answer
55 views

Why does water change from transparent to opaque when it comes out of a tap?

When we open the nozzle of the tap slowly, we observe a fine near-transparent beam of water particles coming down smoothly. If we loosen the nozzle a bit more, rotational effects start to appear, ...
1
vote
3answers
697 views

Bernoulli's law for turbulent flow

Is Bernoulli's law valid for turbulent flow for a non-viscous, non-compressible, non-rotating fluid with isoentropic flow? An ideal fluid has coeffieicent of viscosity=0,which implies that it's ...
0
votes
0answers
13 views

Estimating (or Modelling) an opening of vertically hinged door due to air flow

I am solving a simple looking, but actually difficult fluid dynamics problem. As shown, a hinged door is placed at the bottom of the box-shaped duct. Here, it is possible to assume any friction at ...
0
votes
0answers
50 views

How do I determine the shape of steam?

When you dip a fork into a plate of hot food right off the stove and pull it out again with a forkful of food, it generates water vapour steam from the temperature difference. I am wondering how the ...
1
vote
1answer
960 views

Reynolds number in a wind tunnel

I would like to understand how to calculate the Reynolds number in the test chamber of a wind tunnel. It is known that the Reynolds number for a pipe is: $$Re = \frac{UL}{\nu}$$ where $U$ is the ...
0
votes
2answers
56 views

When was any one liter of Long Island Sound water last in the Atlantic Ocean? [closed]

When was any one liter of Long Island Sound water last in the Atlantic Ocean? The Sound for this model is: Area: 1,268 mi² Mean depth: 63 feet Length 110 miles Eastern opening into the Atlantic is ...
0
votes
0answers
29 views

Most effecient negative shape to create laminar flow

I was looking at laminar flow filters to aid in my mycology work I'm doing. Most filters use an aluminum extrusion with fins. I figured the options out there are pretty expensive for what you get and ...
2
votes
1answer
75 views

Problem about the hypothesis of turbulence from Kolmogorov (1941)

I'm actually studying the famous paper of Kolmogorov (1941) about incompressible turbulence (https://royalsocietypublishing.org/doi/abs/10.1098/rspa.1991.0075), but something struck me and I can't get ...
0
votes
1answer
26 views

Uncertainty Decomposition in velocity signal

I have a timeseries with repeated measured velocity signal (almost periodic signal). To find the mean time-varying velocity, I have decomposed the signal and computed the ensemble-average and the RMSE ...
1
vote
0answers
393 views

Turbulent flow in a pipe - how to compute the friction coefficient $\lambda$

Consider a pipe of diameter $D = 0.01$ m and Length $L = 1.0$ m represented in the figure underneath. At the in- and outlet, the pipe cross-section converges, respectively diverges smoothly. We will ...
1
vote
0answers
64 views

Physical Interpretation of Kolmogorov 5/3 law [duplicate]

The Kolmogorov 5/3 law says that in turbulent flow, the energy $E(k)$ contained in a certain wave number k is proportionate to $k^{-\frac{5}{3}}$. How should one interprete this result in physical ...
4
votes
2answers
45 views

How much will a hole in the wing of a bumblebee affect its flying? [closed]

let's assume the holes are round shape in the middle of both wings. if the size is 1% of the whole wing, how much will be the impact? i assume this is not linear, how much will be affected if the hole ...
1
vote
0answers
22 views

Is there a physical limit to silent quadcopters, and what are the parameters?

Quadcopters can now navigate fairly well indoors. One could imagine many possible uses, including telepresence and security, but which are limited because of the loud noise. Assuming zero 'motor ...
4
votes
1answer
68 views

What exactly sets the scale in Fusion power plants?

In fusion power plants, larger devices are said to achieve fusion more easily, next step tokamaks like DEMO are even larger than ITER. In a quantitative way, what exactly isn't scale invariant in a ...
3
votes
2answers
364 views

How should energy loss in a hydraulic jump be calculated?

The energy loss in a hydraulic jump is still calculated with the old equation of Bresse from year 1860; (I.e., equation 7 in this paper from 2017) $$ \frac{\Delta E}{E_1} = \frac{(\sqrt{1+8Fr^2}-3)^3}...
0
votes
0answers
34 views

Is that reasonable to use kinetic energy and potential energy of a fluid system to define the laminar, transition and turbulent region?

This is my assumption ( I don't know whether it exists or not ): I suppose a fluid system always contains two types of energy, i.e., kinetic energy and potential energy. The kinetic energy of a ...
1
vote
1answer
243 views

What is a precise definition for laminar flow that includes “laminar vortex-shedding”?

I can't find a definition for laminar flow that includes vortex structures. See paper: Numerical calculation of laminar vortex-shedding flow past cylinders and countless others when googled.
2
votes
1answer
423 views

What is the relation between incompressible flow and laminar flow?

I have a small question about dynamics. My textbook shows me the velocity profile for an incompressible flow, which has a parabolic profile. Does this automatically mean it's laminar flow? I don't ...

1
2 3 4 5 6