Factbites
 Where results make sense
About us   |   Why use us?   |   Reviews   |   PR   |   Contact us  

Topic: Prandtl number


Related Topics

In the News (Tue 25 Jun 19)

  
  Prandtl number - Wikipedia, the free encyclopedia
The Prandtl Number is a dimensionless number approximating the ratio of momentum diffusivity and thermal diffusivity.
In heat transfer problems, the Prandtl number controls the relative thickness of the momentum and thermal boundary layers.
The mass transfer analog of the Prandtl number is the Schmidt number.
en.wikipedia.org /wiki/Prandtl_number   (125 words)

  
 ASP Annual Scientific Report 2002 - Scientific Highlights
In the upper part (z < 2) the Prandtl number is 1 in both cases, whereas in the lower part (z > 2) the Prandtl number is 0.25 for the left and 4 for the right case.
It was shown that the Prandtl number has nearly no influence on the penetration depth of a single downflow, whereas the full convection simulations show a significant increase of the overshoot depth with decreasing Prandtl number.
Thus the dependence of the overshoot depths on the Prandtl number is caused by the different thermal adjustment of the mean stratification and not by a change of the deceleration of a single downflow.
www.asp.ucar.edu /asr2002/highlights.htm   (958 words)

  
 [No title]   (Site not responding. Last check: 2007-10-21)
In physics, the P clet number is a dimensionless number relating the forced convection of a system to its heat conduction.
In fluid mechanics, the Rayleigh number for a fluid is a dimensionless number associated with the heat transfer within the fluid.
When the Rayleigh number is below the critical value for that fluid, heat transfer is primary in the form of conduction; when it exceeds the critical value, heat transfer is primarily in the form of convection.
www.worldhistory.com /wiki/P/Prandtl-number.htm   (295 words)

  
 Prandtl number: Facts and details from Encyclopedia Topic   (Site not responding. Last check: 2007-10-21)
Mach number (ma) is defined as a ratio of speed to the speed of sound in the medium in case....
The reynolds number is the most important dimensionless number in fluid dynamics and provides a criterion for determining dynamic similarity....
The weissenberg number is a dimensionless number used in the study of viscoelastic flows....
www.absoluteastronomy.com /encyclopedia/p/pr/prandtl_number.htm   (493 words)

  
 Learn more about Fluid mechanics in the online encyclopedia.   (Site not responding. Last check: 2007-10-21)
The foundational axioms of fluid mechanics are the conservation laws, specifically, conservation of mass, conservation of momentum (also known as Newton's second law), and conservation of energy These are based on classical mechanics and are violated in relativistic mechanics.
The Reynolds number can be used to evaluate whether viscous or inviscid equations are appropriate to the problem.
Turbulence is instead modeled using one of a number of turbulence models and coupled with a flow solver that assumes laminar flow outside a turbulent region.
www.onlineencyclopedia.org /f/fl/fluid_mechanics_1.html   (961 words)

  
 Péclet number - Wikipedia, the free encyclopedia
In physics, the Péclet number is a dimensionless number relating the forced convection of a system to its heat conduction.
It is equivalent to the product of the Reynolds number with the Prandtl number.
There are various definitions of the Péclet number.
en.wikipedia.org /wiki/Peclet_number   (105 words)

  
 Rayleigh number   (Site not responding. Last check: 2007-10-21)
When the Rayleigh number is below critical value for that fluid heat transfer primary in the form of conduction ; when it exceeds the critical value transfer is primarily in the form of convection.
The Rayleigh number is defined as product of the Grashof number which describes the relationship between buoyancy and inertia within a fluid and the Prandtl number which describes the relationship between the viscosity of a fluid and its temperature.
In geophysics the Rayleigh number is of fundamental it indicates the presence and strength of within a fluid body such as the which is a solid but which behaves a fluid over geological time scales.
www.freeglossary.com /Rayleigh_number   (416 words)

  
 Ludwig Prandtl Passage @ FolkArtMuseum.com (Folk Art Museum)   (Site not responding. Last check: 2007-10-21)
He was a pioneer of aerodynamics, and developed the mathematical basis for the fundamental principles of subsonic aerodynamics in the 1920s.
He was also the eponym of the Prandtl number.
In 1901 Prandtl became a professor of mechanics at a technical school in Hannover.
www.folkartmuseum.com /encyclopedia/Ludwig_Prandtl   (659 words)

  
 [No title]
Besides all, the Grashof number (Gr) is proportional to the characteristic temperature difference (difference of the temperatures at the vertical walls in this case).
The task of the GAMM benchmark is to calculate the critical value of the Grashof number which corresponds to a bifurcation from steady to oscillatory state of the flow.
Number of basis functions in horizontal and vertical directions is the only data to be supplied.
www.spec.org /cpu/CFP2000/178.galgel/docs/README   (1454 words)

  
 Clarkson U | TMFL | DJS Research | Buoyancy-induced flows within a two-dimensional, square enclosure.
As the Prandtl number is decreased, the lines of constant vorticity become coincident with the streamlines within the interior region of the enclosure.
with Prandtl numbers of order one or smaller, two distinct flow patterns in the corner are identified, i.e., a temperature overshoot and a standing wave.
At a higher Prandtl number of 7.00, no evidence of this corner flow structure is observed.
www.clarkson.edu /fluidflow/djs/ms.html   (280 words)

  
 Aviation and Aerodynamics: Ludwig Prandtl
Direct consequences of the theory were the introduction of the Reynolds number in fluid mechnanics, the effects of the skin friction of fluid flow, many heat transfer problems, the solution of the d'Alembert paradox.
Prandtl's other contributions include: the introduction of the Reynolds number in fluid mechanics, airfoils and wing theory (including theories of aerodynamic interference, wing-fuselage, wing-propeller, biplane, etc); fundamental studies in the wind tunnel, high speed aerodynamics (correction formula for subsonic compressible flows), theory of turbulence.
Prandtl L. Recent progress in the theory of air flow as applied to aeronautics, NACA TM-55, 1922.
www.aerodyn.org /People/prandtl.html   (488 words)

  
 Dipprey, Duane F. (1961-01-01) An experimental investigation of heat and momentum transfer in smooth and rough tubes at ...
A Prandtl number range of 1.20 to 5.94 was investigated by adjusting the bulk temperature of the water.
Results were obtained for Reynolds numbers from 6 x [...] to 5 x [...] and from 1.4 x [...] to 1.2 x [...] at the lowest and highest Prandtl number respectively.
An exception to this general behavior occurs at high Prandtl number in the region of transition between the "smooth" and the "fully rough" [...] characteristic.
etd.caltech.edu /etd/available/etd-04082005-110724   (296 words)

  
 Astrophys. Inst. Potsdam - Magnetohydrodynamics
Prandtl number, upper curves in the graph, the Hartmann number is a measure of the magnetic field strength).
Now we studied MHD Taylor-Couette flows for large Prandtl numbers, and there is indeed a subcritical excitation of Taylor vortices due to the presence of magnetic fields.
The magnetic Prandtl numbers in astrophysical objects are indeed orders of magnitudes larger than those of terrestrial conducting fluids (Hg 10^-7, Ga 10^-6, Na 10^-5).
www.aip.de /image_archive/Magnetohydrodynamics.html   (887 words)

  
 Research Projects Ready to Bid
The geometric parameters studied were number of ribs (18 to 48), helix angle (25 to 45 deg.) and rib height to diameter ratio (e/d: 0.0212 to 0.0353).
The geometric parameters studied were number of fins (60 to 70), helix angle (8 to 25) and fin height to diameter ratio (e/d: 0.11 to 0.22).
The data was taken in a smooth tube, the Reynolds number was ranged from 280 to 49,000 and the Prandtl number was ranged from 4 to 158.
xp20.ashrae.org /RESEARCH/1280-TRP.htm   (3139 words)

  
 AERADE
The data are presented in tabular form at intervals of either 20 K or 20 degree Celsius and as equations (except for the Prandtl number).
ESDU 03008 presents values of thermal conductivity, viscosity, isobaric specific heat capacity and Prandtl numbers of the vapours of 17 halogenated propanes, butanes, ethylenes and benzenes in the dilute or ideal gas.
The data are presented in tabular form at intervals of both 20 K and 20 degrees Celsius and as equations (except for the Prandtl number).
aerade.cranfield.ac.uk /subject-listing/esdu/ES33.html   (1097 words)

  
 MMA Memo 203 Forced Air Cooling at High Altitude
Using the Re number calculated in the average Nu number formulae, the results are shown in Figure 3.
The characteristic length of a cylinder perpendicular to the flow is its diameter.
For a characteristic length of 0.02 m, the Re number is reduced by 50 times that for a characteristic length of 1 m,.
www.alma.nrao.edu /memos/html-memos/alma203/memo203.html   (1935 words)

  
 Fluid dynamics   (Site not responding. Last check: 2007-10-21)
The foundational axioms of fluid dynamics are the conservationlaws, specifically, conservation of mass, conservationof momentum, (also known as Newton's second law orthe balance law), and conservation of energy.
The Reynolds number can be used to evaluate whether viscous or inviscid equations are appropriateto the problem.
Turbulence is instead modeled using one of a number of turbulence models and coupledwith a flow solver that assumes laminar flow outside a turbulent region.
www.therfcc.org /fluid-dynamics-59.html   (858 words)

  
 Dimensionless Numbers in Heat Transfer   (Site not responding. Last check: 2007-10-21)
For flow over a flat plate, the critical Reynolds number is observed to vary between 1e+5 to 3e+6 depending on the turbulence level in the free stream and the roughness of the surface.
Heat transfer gurus have invented another dimensionless number called the Prandtl number which is a grouping of the properties of the fluid but it has a significance to our discussion.
The Grashof number is the ratio of buoyancy forces to the viscous forces.
www.coolingzone.com /Content/Library/Tutorials/Tutorial%201/DNHT.html   (2128 words)

  
 [No title]
The GAMM benchmark considers fixed values of the Prandtl number and the aspect ratio (0.015 and 4 respectively), and varies the boundary conditions.
A relatively small number of degrees of freedom makes it possible to study linear stability of steady solutions, requiring solution of an eigenvalue problem, which is usually impossible for an arbitrary CFD code.
However, only the number of basis functions in horizontal and vertical directions is provided in the SPEC input, the other data taking default values.
www.spec.org /cpu/CFP2000/178.galgel/docs/178.galgel.txt   (755 words)

  
 boeck
Non-dimensional control parameters are the Marangoni number Ma describing the strength of the thermo-capillary forcing, the Prandtl number P, and the aspect ratio.
We have performed simulations with a small Prandtl number P = 0.1 for Marangoni numbers up to 100 000 in a periodic box where the horizontal dimension equals twice the height of the cell [3].
We could show that the limit of zero Prandtl number does not lead to the same singular behavior as in the two-dimensional case, where an unbounded exponential growth of the flow amplitude occurs above a Marangoni number close to the linear stability threshold.
www.tu-dresden.de /mw/ilr/for_berichte/boeck.html   (797 words)

  
 Mailgate: sci.physics.computational.fluid-dynamics: Re: Turbulent Prandtl number for nitrogen   (Site not responding. Last check: 2007-10-21)
Mailgate: sci.physics.computational.fluid-dynamics: Re: Turbulent Prandtl number for nitrogen
Following the > definition of the Prandtl number I was able to calculate the (laminar) > Prandtl number (Pr=0.67) but I don't know how to scale the laminar > number to obtain the turbulent one.
Often, a turbulence Prandtl number of 0.7-0.9 is used in numerical simulations.
mailgate.supereva.it /sci/sci.physics.computational.fluid-dynamics/msg01821.html   (173 words)

  
 [No title]
The discrepancies between theory and experiment may be due to differences between the experiment parameters(M/R = 8 at Prandtl number of 100) and those of theory (M/R = 2.7 at infinite Prandtl number).
For small (large) wave numbers the defect moves in a direction that adds (removes) two rolls to (from) the system and hence increases (decreases) the overall wave number to a value closer to the center of the stable band.
Motion in the opposite direction where the wave number is being increased is qualitatively different - the path is smoother and there is less of a time dependence in the speed.
www.physics.gatech.edu /schatz/control/benard.html   (538 words)

  
 NACA UK Mirror report description page   (Site not responding. Last check: 2007-10-21)
Although it approaches zero when the Prandtl number approaches zero, its dependence on the Prandtl number is not large for Prandtl numbers of order unity and larger.
This type of Prandtl number dependence is typical for many of the other results depending on both velocity and temperature fluctuations.
For example, for small Prandtl numbers the double temperature correlation falls off much more slowly with separation distance than the velocity correlation does, while for large Prandtl numbers the opposite is true.
naca.central.cranfield.ac.uk /report.php?NID=7266   (276 words)

  
 [No title]   (Site not responding. Last check: 2007-10-21)
A numerical and analytical study of the free convection thermal boundary layer or wall jet at finite Prandtl number is performed to understand the mechanisms of the separation of a high Prandtl number thermal boundary layer flows.
The velocities and pressure in the lower deck are obtained thus determining the temperature distribution in the reversed flow zone.
The asymptotic structure of the flow downstream of separation for the temperature is analysed indicating a functional dependence on the streamfunction in the slowly recirculating inviscid core.
www.cis.jhu.edu /~tilak/istp.html   (147 words)

  
 [No title]   (Site not responding. Last check: 2007-10-21)
The thermal field of a separating wall jet is studied for a range of values of the Prandtl number of the fluid.
The structure of the jet near the point of separation is described by a free interaction in which the fundamental problem is to solve the boundary-layer equations in a viscous sublayer close to the wall.
The large Prandtl number limit is considered in detail and it is shown that the main variation of the thermal field occurs within a region in the immediate neighbourhood of the point of separation.
www.cis.jhu.edu /~tilak/jem2000.html   (178 words)

  
 ipedia.com: Fluid dynamics Article   (Site not responding. Last check: 2007-10-21)
In order to determine whether to use conventional fluid dynamics (a subdiscipline of continuum mechanics) or statistical mechanics, the Knudsen number is evaluated for the problem.
The foundational axioms of fluid dynamics are the conservation laws, specifically, conservation of mass, conservation of momentum, (also known as Newton's second law or the balance law), and conservation of energy.
In order to determine whether to use compressible or incompressible fluid dynamics, the Mach number of the problem is evaluated.
www.ipedia.com /fluid_dynamics.html   (950 words)

  
 Viscous heating of sensor tips
C at 1 m/s and increases as the square root of Prandtl number and velocity squared.
Based on Prandtl number scaling, the error should be greatest in laminar flows and decrease with embedded turbulence by up to a factor of 3 in 0
However, the scaling of the viscous heating results with Prandtl number do predict a decrease in the wall temperature as turbulence develops within a constant mean flow and the Prandtl number decreases toward 1.
www.seabird.com /technical_references/viscous.htm   (2378 words)

  
 Prandtl Number   (Site not responding. Last check: 2007-10-21)
Ludwig Prandtl, a German teacher and scientist, in 1904, conceived the idea of a boundary layer that adjoins the surface of a body moving through a fluid.
The treatment of the boundary layer near the solid boundary as a viscous fluid and the flow outside the boundary layer as a frictionless fluid was one of Prandtl
In this article, the role of Prandtl number in heat transfer applications and some of the associated correlations are discussed.
www.dekker.com /sdek/165377615-38416014/abstract~content=a713499275~db=enc   (556 words)

  
 Rice University - CENG 403 - Prandtl Numbers with prcalc and mixpr   (Site not responding. Last check: 2007-10-21)
Rice University - CENG 403 - Prandtl Numbers with prcalc and mixpr
The Prandtl Number = cp*m/k is a dimensionless quantity that plays an important role in heat exchange.
mixpr(zs,T,j) finds the Prandtl number for a low density gas mixture zs gives the mol fraction of each compound T gives the temperature in the units of Tdeg j gives the indices of the compounds (if missing it includes all compounds.
www.owlnet.rice.edu /~chbe402/ed1projects/prandtl.html   (187 words)

  
 Monday afternoon, 20 November 1995, 16:51   (Site not responding. Last check: 2007-10-21)
The type of instability that occurs is strongly dependent on the Prandtl number of the liquid.
Both the primary and secondary bifurcations persist for zero Prandlt number, indicating that both of the instabilities are purely hydrodynamical.
For intermediate Prandlt numbers the flowfield bifurcates directly to an oscillatory state as for larger Prandtl numbers but the structure of the bifurcated solution is different from the higher Prandlt number state making us inclined to belive that there is an additional branch of solutions for this range of Prandtl numbers.=20
flux.aps.org /meetings/BAPSDFD95/abs/SGg01.html   (231 words)

Try your search on: Qwika (all wikis)

Factbites
  About us   |   Why use us?   |   Reviews   |   Press   |   Contact us  
Copyright © 2005-2007 www.factbites.com Usage implies agreement with terms.