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.
Questions tagged [turbulence]
380 questions
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Why does rainwater form moving waves on the ground? Is there a name for this effect?
A while ago it was raining and I noticed that, on sloped pavement, water was flowing in very regular consistent periodic waves, as you see below.
However, I realized I had no idea why this should be happening. There was nothing uphill actually…
user541686
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Turbulent spacetime from Einstein equation?
It is well known that the fluid equations (Euler equation, Navier-Stokes, ...), being non-linear, may have highly turbulent solutions. Of course, these solutions are non-analytical. The laminar flow solutions (Couette flow for example) may be…
Cham
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Why are aerodynamic / streamlined shapes always stumpy at the front?
I'm building an autonomous boat, to which I now add a keel below it with a weight at the bottom. I was wondering about the shape that weight should get. Most of the time aerodynamic shapes take some shape like this:
The usual explanation is that…
kramer65
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What is the mystery of turbulence?
One of the great unsolved problems in physics is turbulence but I'm not too clear what the mystery is. Does it mean that the Navier-Stokes equations don't have any turbulent phenomena even if we solve it computationally? Or does it mean we simply…
cspirou
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Have we figured out how to analyze turbulent fluids?
I was surprised to read that we don't know how to analyze turbulent fluids. On page 3-9 of The Feynman Lectures on Physics (Volume One), Feynman writes:
Finally, there is a physical problem that is common to many fields, that is very old, and that…
25
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What is enstrophy?
In turbulence, the enstrophy of a flow in a domain $\mathcal{D} \subset \mathbb{R}^{D}$
$$
\mathcal{E} = \int_{\mathcal{D}} |\vec{\nabla} \times \, \vec{v}|^2 d^{D}x
$$
appears sometimes, it's cool and has cute properties in 2d (see this answer…
Georg Sievelson
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About turbulence modeling
I have some questions about this paper:
Lagrangian/Hamiltonian formalism for description of Navier-Stokes fluids. R. J. Becker. Phys. Rev. Lett. 58 no. 14 (1987), pp. 1419-1422.
After reading the paper, the question arises how far can we…
21
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What causes wind gusts?
A difference in temperature causes different pressures, air travel from high to low pressure, and that is wind.
We can even produce wind in an experiment like in this video. In this video, what is the way it can produce gusts?
To increase wind…
22flower
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20
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4 answers
How to estimate the Kolmogorov length scale
My understanding of Kolmogorov scales doesn't really go beyond this poem:
Big whirls have little whirls that feed on their velocity, and little whirls have lesser whirls and so on to viscosity. - Lewis Fry Richardson
Th smallest whirl according…
mart
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Why is an airfoil shaped like a teardrop?
I understand the reason airfoils are cambered on the top: to create lift. But one would assume this would result in aircraft wings having a semicircle-shaped design. Why is the cross-section of an airfoil instead more reminiscent of a teardrop on…
James Davis
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Occurrence of turbulence in fluid dynamics from the equations of motion?
How can it be shown that turbulence occurs in fluid dynamics?
I think people imply that it develops because of the $\text{rot}$ terms in the equations of motion, i.e. the Navier-Stokes equations, but I don't see how. Of course, these…
Nikolaj-K
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17
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1 answer
Kolmogorov/Energy spectrum for turbulent boundary layer
Previously, I have calculated energy spectrum for 3D isotropic turbulent flow data which is equally spaced in all three directions and then to compute the energy spectrum, one performs Fourier transform and then accumulates energy located in…
Sidhha
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16
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How to calculate the upper limit on the number of days weather can be forecast reliably?
To put it bluntly, weather is described by the Navier-Stokes equation, which in turn exhibits turbulence, so eventually predictions will become unreliable.
I am interested in a derivation of the time-scale where weather predictions become…
Daniel Grumiller
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16
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4 answers
Can a Styrofoam box bounce back into a moving van?
I just came across this video. A styrofoam box falls out of a moving van, bounces off the road and lands back in the van.
How can the box land back so precisely inside the van?!
Usually, I would consider these type of videos as bogus. But the fact…
AlphaLife
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How fast would a truck have to go to pull a pedestrian onto the road?
Let's suppose a pedestrian P is walking or standing next to a highway.
Suppose a truck T will drive by the said pedestrian at speed V leaving distance L between the two.
Assuming L is a reasonably small finite size how would one calculate the…
Etheryte
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