Velocity and Temperature Fields Measurement of Natural Convection Flow Using Thermochromic Liquid Crystals

2005 ◽  
Author(s):  
Vale´rie Me´nard ◽  
Adel Stitou ◽  
Ste´phane Le Masson ◽  
David No¨rtersha¨user ◽  
Pierre Millan
Keyword(s):  
Liquid Crystal ◽  
Natural Convection ◽  
Particle Deposition ◽  
Temperature Fields ◽  
Convection Flow ◽  
Simple Relationship ◽  
Natural Convection Flow ◽  
Calibration Methods ◽  
Intensity Response ◽  
Velocity And Temperature Fields

Based on a particular property of some liquid crystal to reflect a specific wavelength for a specific temperature, Particle Image Velocimetry and Thermometry (PIVT) is a method allowing to measure simultaneously velocity and temperature fields. In a first part, this study discusses PIVT calibration methods and especially the effect of liquid crystal particle deposition on hue and intensity response. An experimental set-up is designed and the results confirm the high variations of intensity response with time and the need to use a simple relationship between hue and temperature. In a second place, these results are used to apply PIVT to an unsteady natural convection flow in a cavity containing an internal heat source.

On transition mechanisms in vertical natural convection flow

1974 ◽  
Vol 66 (2) ◽  
pp. 309-337 ◽  
Author(s):  
Yogesh Jaluria ◽  
Benjamin Gebhart
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Velocity Field ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Temperature Fields ◽  
Convection Flow ◽  
Transition Regime ◽  
Natural Convection Flow ◽  
Velocity And Temperature Fields

An experimental investigation has been made of the processes occurring during the natural transition from laminar to turbulent flow of natural convection flow of water adjacent to a flat vertical surface where the surface heat flux is uniform. Measurements of both the velocity and temperature fields were made over wide ranges of the heat flux and at various downstream locations. Of principal interest were the definitions of the boundaries of the transition regime and their determination at several values of the surface heat flux. The interaction of the velocity and temperature fields during transition was measured. Our results show that transition events are not correlated in terms of the Grashof numberG*. The formG*/xn, wherenis of order ½ was found to give satisfactory correlations. Measurements of the frequency and growth rate of disturbances indicate the primacy of the velocity field during transition and show that the growth of turbulence in the temperature field lags behind that in the velocity field. The study of the turbulence growth, in terms of intermittency factors in both the velocity and temperature fields, resulted in unambiguous criteria for the boundaries of the transition regime. Our results suggest a kinetic energy flux parameterEand a single value closely correlates both our measurements of the onset of transition as well as those from all past studies known to us, for both different fluids and heating conditions.

A Pseudospectral Analysis of Laminar Natural Convection Flow and Heat Transfer Between Two Inclined Parallel Plates

2006 ◽  
Author(s):  
Serkan Kasapoglu ◽  
Ilker Tari
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Boundary Conditions ◽  
Boussinesq Approximation ◽  
Temperature Fields ◽  
Convection Flow ◽  
Parallel Plates ◽  
Natural Convection Flow ◽  
Constant Wall Temperature ◽  
Laminar Natural Convection

Three dimensional laminar natural convection flow of and heat transfer in incompressible air between two inclined parallel plates are analyzed with the Boussinesq approximation by using spectral methods. The plates are assumed to be infinitely long in streamwise (x) and spanwise (z) directions. For these directions, periodic boundary conditions are used and for the normal direction (y), constant wall temperature and no slip boundary conditions are used. Unsteady Navier-Stokes and energy equations are solved using a pseudospectral approach in order to obtain velocity and temperature fields inside the channel. Fourier series are used to expand the variables in × and z directions, while Chebyshev polynomials are used to expand the variables in y direction. By using the temperature distribution between the plates, local and average Nusselt numbers (Nu) are calculated. Nu values are correlated with φ, which is the inclination angle, and with Ra·cosφ to compare the results with the literature.

scholarly journals Natural Convection Flow Of An Electrically Conducting Fluid In A Rectangular Cavity Having Internal Energy Sources With Linearly Heated Bottom Wall

2013 ◽  
Vol 32 ◽  
pp. 61-73
Author(s):  
M Obayedullah ◽  
M M K Chowdhury
Keyword(s):  
Natural Convection ◽  
Rectangular Cavity ◽  
Conducting Fluid ◽  
Bottom Wall ◽  
Temperature Fields ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Electrically Conducting ◽  
Electrically Conducting Fluid ◽  
Rayleigh Numbers

Natural convection flow in a rectangular cavity containing internally heated and electrically conducting fluid has been investigated numerically. The bottom wall of the cavity is linearly heated whereas the top wall is well insulated. The left and right vertical walls are maintained at constant hot and cold temperature respectively.Results have been obtained with respect to Rayleigh numbers and Hartmann numbers. Flow and temperature fields for these cases have been studied. Average Nusselt numbers at hot, cold and linearly heated bottom wall have been calculated. It is found that the temperature, fluid flow and heat transfer strongly depend on internal and external Rayleigh numbers and Hartmann numbers. DOI: http://dx.doi.org/10.3329/ganit.v32i0.13648 GANIT J. Bangladesh Math. Soc. (ISSN 1606-3694) 32 (2012) 61-73    

NATURAL CONVECTION STUDY IN AN ENCLOSURE WITH DIFFERENT ASPECT RATIOS

2007 ◽  
Vol 18 (12) ◽  
pp. 1903-1923 ◽  
Author(s):  
YI DONG ◽  
QINGLAN ZHAI
Keyword(s):  
Natural Convection ◽  
Present Model ◽  
Distribution Functions ◽  
Temperature Fields ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Aspect Ratios ◽  
Boltzmann Method ◽  
Rayleigh Numbers ◽  
Good Agreement

Natural convection in an enclosure with different ratios are investigated with the lattice Boltzmann method, and double distribution functions (DDF) are proposed to simulate the velocity and the temperature fields. Meanwhile, compared with other existing results, we studied the effect of the different aspect ratios on heat transfer, and 2D numerical simulation of natural convection flow in a square cavity are performed at Rayleigh numbers 103–106 with fixed Prandtl number 0.71 in detail. The numerical results of the Nusselt number along the two sidewalls and the maximum velocities along the horizontal and vertical lines through the cavity center are in good agreement with existing results, which shows the accuracy of the present model.

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