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Turbulent flow

on Tue Apr 05, 2016 12:19 pm


Fluid Mechanics and
Turbulent Flow
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TurbuLence

on Tue Apr 05, 2016 12:58 pm
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Turbulent Flow

on Tue Apr 05, 2016 3:54 pm
R.F. L3-7 wrote:
Finally, there is a physical problem that is common to many fields, that is very old, and that has not been solved. It is not the problem of finding new fundamental particles, but something left over from a long time ago—over a hundred years. Nobody in physics has really been able to analyze it mathematically satisfactorily in spite of its importance to the sister sciences. It is the analysis of circulating or turbulent fluids. If we watch the evolution of a star, there comes a point where we can deduce that it is going to start convection, and thereafter we can no longer deduce what should happen. A few million years later the star explodes, but we cannot figure out the reason. We cannot analyze the weather. We do not know the patterns of motions that there should be inside the earth. The simplest form of the problem is to take a pipe that is very long and push water through it at high speed. We ask: to push a given amount of water through that pipe, how much pressure is needed? No one can analyze it from first principles and the properties of water. If the water flows very slowly, or if we use a thick goo like honey, then we can do it nicely. You will find that in your textbook. What we really cannot do is deal with actual, wet water running through a pipe. That is the central problem which we ought to solve some day, and we have not.
A poet once said, “The whole universe is in a glass of wine.” We will probably never know in what sense he meant that, but it is true that if we look at a glass of wine closely enough we see the entire universe. There are the things of physics: the twisting liquid which evaporates depending on the wind and weather, the reflections in the glass, and our imagination adds the atoms. The glass is a distillation of the earth’s rocks, and in its composition we see the secrets of the universe’s age, and the evolution of stars. What strange array of chemicals are in the wine? How did they come to be? There are the ferments, the enzymes, the substrates, and the products. There in wine is found the great generalization: all life is fermentation. Nobody can discover the chemistry of wine without discovering, as did Louis Pasteur, the cause of much disease. How vivid is the claret, pressing its existence into the consciousness that watches it! If "our" minds, for some convenience, divide this glass of wine, this universe, into parts—physics, biology, geology, astronomy, psychology, and so on—remember that nature does not know it! So let us put it all back together, not forgetting ultimately what it is for. Let it give us one more final pleasure: drink it and forget it all!

Fluid flows  in nature   normally depart from laminarity  and are turbulent
in the majority of cases, including flows around bodies such as airplanes,
vehicles, ships, and in internal flows such as in ducts, turbomachines, 
propulsors, and in blood circulation in the human body. Furthermore
the boundary layer in the earth's atmosphere is turbulent and so is the flow 
of water in rivers and canals ,  the jet streams in the upper troposphere  and 
the water currents below the surface of the oceans.Cumulus clouds are also
in turbulent motion ; the Gulf Stream is a  turbulent wall-jet kind of flow. 
The photosphere of the sun and the photospheres of similar stars are in 
turbulent motion; interstellar clouds (nebulae) are turbulent; the wake of
 the earth in the solar wind is  presumably a turbulent wake. Laminarity 
is the anomaly and not the standard. The parameter which is fundamental 
to the transition from laminarity to turbulence is  the Reynolds  number,  
i.e.,  the ratio of inertial  to viscous forces.                     Dimensionaly

where m is the mass, a the acceleration, Fv the viscous force,
U a characteristic velocity, L a characteristic lenght , τ the 
shear stress , μ the dynamic viscosity coeficient, v the
kinematic viscosity coefficient, and ρ the density.
The Reynolds number is a parameter which carries
information on the overall behavior of the flow field
When the Reynolds number is below a critical value
ReC the viscous forces are high enough to smooth 
instabilities in the flow. Whenever Re ReC  the
flow will start to exhibit all the features of 
developed turbulence.
These features establish the major differences
between laminar and turbulent flows:
extreme sensitivity to initial and boundary conditions
unpredictability and randomness
wide range of structures (scales) in space and time
fully three-dimensional nature
higher diffusion compared to the laminar case
presence of cross-fluctuating terms among
fluid mechanics variables.
The sensitivity to initial conditions is the key point
for the understanding of the behavior of turbulent flows;
it is not possible, even in principle, to control the BC and 
IC to an arbitrarily small degree, especially if they pertain 
to a turbulent flow field (such as the inlet conditions for a
channel). In comparison to laminar flow, a turbulent flow
will exhibit a substantial (not only apparent due to our 
ignorance) unpredictable andrandom nature at any point
and any time which originates from this high sensitivity 
to BC and IC; this also produces correlated  fluctuations 
among the fluid-mechanics variables.   These complex 
behaviors seem to prevent the possibility of an analy-
tical approach when dealing with turbulent flows;in 
fact , from the mathematical point of view , there is 
still no theorem proving the existence and uniquene-
ss  of solutions to the Navier -Stokes equations in fully
3-dimensional conditions (as in turbulent flows), for arb-
itrary time intervals,  whatever the Reynolds number.

* Abbreviations
IC initial condition
BC boundary condition

Millennium Problems : Navier–Stokes Equation
http://www.claymath.org/sites/default/files/navierstokes.pdf


Last edited by Manhattan Gandhi on Tue Apr 05, 2016 7:00 pm; edited 1 time in total
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TurbuLence

on Tue Apr 05, 2016 4:21 pm


https://ctr.stanford.edu/

https://ctr.stanford.edu/ctr-video

http://www.efluids.com/



NCFMF . National Committee for Fluid Mechanics Films 
http://web.mit.edu/hml/ncfmf.html , 1969.





This visualization shows ocean surface currents around the 
world during the period from June 2005 through Dec. 2007

http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003827/
http://www.nasa.gov/topics/earth/features/perpetual-ocean.html

Visualization of a geophysical turbulent flow:The Gulf Stream
and eddies in the western North Atlantic Ocean:

http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=3913


Last edited by Manhattan Gandhi on Tue Apr 05, 2016 4:35 pm; edited 1 time in total
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NASA Langley | Study at Wallops Island

on Tue Apr 05, 2016 4:32 pm


Wake Vortex Study at Wallops Island.

NASA Langley Research Center
Turbulence Modeling Resource
https://turbmodels.larc.nasa.gov/

C-5A Wing Vortice tests at NASA Langley Research Center
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TurbuLence

on Tue Apr 05, 2016 7:13 pm


Leonardo da Vinci’s illustration of the swirling flow of turbulence.
Windsor Castle, Royal Library


The sketch
above--- a free water jet issuing from a square hole into a pool---represents perhaps the world's
first use of visualization as a scientific tool to study a turbulent flow. Leonardo wrote (translated
by Ugo Piomelli, University of Maryland), "Observe the motion of the surface of the water,which
resembles that of hair, which has two motions, of which one is caused by the weight of the hair,
the other by the direction of the curls; thus the water has eddying motions,  one part of which is
due to the principal current, the other to the random and reverse motion."  According to  John L.
Lumley, Cornell University, Leonardo may have prefigured the now famous Reynolds turbulence
decomposition nearly 400 years prior to Osborne Reynolds' own flow visualization and analysis.
In describing the swirling water motion behind a bluff body,       da Vinci provided the earliest
reference to  the importance of vortices in fluid motion: "So moving water strives to maintain
the course pursuant to the power which occasions it and, if it finds an obstacle in its path,
completes the span of the course it has commenced by a circular and revolving movement."
Leonardo accurately sketched the pair of quasi-stationary, counterrotating vortices in the midst
of the random wake. Finally, da Vinci's words "... The small eddies are almost numberless, and
large things are rotated only by large eddies and not by small ones, and small things are turned
by both small eddies and large" presage Richardson's cascade, coherent structures, and large-
eddy simulations, at least.            .Reference: M. Gad-el-Hak: Flow Control: Passive, Active, and
Reactive Flow Management, Cambridge University Press, 2000.


Last edited by Manhattan Gandhi on Tue Apr 05, 2016 7:27 pm; edited 2 times in total
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Leonardo da Vinci

on Tue Apr 05, 2016 7:23 pm
http://www.giss.nasa.gov/research/briefs/canuto_01/



A rigid obstacle in flowing water creates wake turbulence,   a fact noted and sketched
by Leonardo da Vinci in 1509. The passage of a moving body through a static medium
has the same effect, and the turbulence can be used to accelerate a following body.
What is true for a boat in water also applies to electrons passing through a gas,   a
fact exploited by Blumenfeld et al.1 in their high-energy plasma wakefield accelerator.


THE ROYAL COLLECTION © 2007, HER MAJESTY QUEEN ELIZABETH II
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Labrador Current

on Tue Apr 05, 2016 7:26 pm


View of the Labrador Current, 8 transatlantic flight minutes [130km]
east of Belle Isle,  taken on a flight from London to Chicago. 

Terra, 8 May 2003, 1535 UTC: 
Ice and contrails along Labrador coast, Canada

 
3 May 2013

6 April 2008
 
Satellite Terra - Ice in the Labrador Current - http://terra.nasa.gov/
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Reynolds Number , Interstellar Turbulence

on Tue Apr 05, 2016 7:41 pm


Last edited by Manhattan Gandhi on Wed Apr 06, 2016 1:09 am; edited 1 time in total
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Hiroshige

on Tue Apr 05, 2016 8:44 pm


Utagawa Hiroshige - View of the Whirlpools at Awa triptych, 1857



Naruto Whirlpool 
Utagawa Hiroshige
Edo , Tokyo
[ca. 1853]




六十余州名所図会 阿波 鳴門の風波[detail2]
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Spiral Galaxies

on Tue Apr 05, 2016 8:56 pm
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TYPHOONS

on Tue Apr 05, 2016 9:31 pm
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The Starry Night

on Tue Apr 05, 2016 9:46 pm
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Re: Turbulent flow

on Tue Apr 05, 2016 10:02 pm


The NASA/ESA Hubble Space Telescope has been observing the
V838 Mon light echo since 2002. Each new observation of the light
echo reveals a new and unique "thin-section" through the interstellar
dust around the star. This video morphs images of the light echo from
the Hubble taken at multiple times between 2002 and 2006. The numerous
whorls and eddies in the interstellar dust are particularly noticeable. Possibly
they have been produced by the effects of magnetic fields in the space between
the stars.

Light echo around V838 Monocerotis In January 2002
Images showing the expansion of the light echo 4 March 2004
http://apod.nasa.gov/apod/ap040305.html
V838 Monocerotis stages of expansion beginning from May 2002 to October 2004



Image Sequence of V838 Monocerotis Epochs
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Pictures

on Tue Apr 05, 2016 10:08 pm


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Pictures 2

on Tue Apr 05, 2016 10:25 pm
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神奈川沖浪裏

on Tue Apr 05, 2016 10:34 pm


神奈川沖浪裏 The Great Wave off Kanagawa .
Hokusai 1829


Kaijo no Fuji, from the second volume of One Hundred Views of Mount Fuji, 1834.
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Moskstraumen MaelströM , Edgar Allan Poe , Maelstrom , Nautilus

on Tue Apr 05, 2016 11:15 pm
Riding the whirlpools of the world's strongest tidal current at Saltstraumen, Norway
Saltstraumen Maelstrom

Maelstrom of Saltstraumen
  The maelstrom off Norway,
  as illustrated by Olaus Magnus
  on the Carta Marina , 1539.
https://s-media-cache-ak0.pinimg.com/8683de003b1e54d40ec.jpg
https://gr.pinterest.com/abebaruck/whirlpools/

 
 Harry Clark , 1919 
 "A Descent into the Maelström"
 Edgar Allan Poe.


--------------------------------------


 : A Descent into the Maelström , 1841 , by Edgar Allan Poe
------------------------------------------------------------------------------
Moskstraumen Maelström



At the end of 20,000 Leagues Under the Sea (1870) Captain Nemo disappeared
sending his Nautilus submarine into the Maelström.      ( Nemo and Nautilus 
survived as we know from "the Mysterious Island"). The "Norway maelström" 
is also mentioned in Herman Melville's Moby-Dick.


 


Last edited by Manhattan Gandhi on Wed Apr 06, 2016 12:03 am; edited 2 times in total
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Beneath Jupiter

on Tue Apr 05, 2016 11:34 pm
Beneath Jupiter



Cloud Swirls around Southern Jupiter from Juno 
https://apod.nasa.gov/apod/image/1702/JupiterSouth_JunoPeach_1200.jpg


Swirling Storm System / Cassini Spacecraft Nov 2000.

Red Spot Turbulence :
https://pds.jpl.nasa.gov/planets/captions/jupiter/grsturb.htm
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