scholarly journals Natural convection for anomalous density variation of water: numerical benchmark

2005 ◽  
Vol 5 (3/4/5) ◽  
pp. 158 ◽  
Author(s):  
T. Michalek ◽  
T.A. Kowalewski ◽  
B. Sarler
Keyword(s):  
Natural Convection ◽  
Density Variation ◽  
Anomalous Density

Natural Convection in a Horizontal Cavity Partially Occupied by a Porous Media Saturated by a Coolant Liquid

2006 ◽  
Author(s):  
Fakhreddine S. Oueslati ◽  
Rachid Bennacer ◽  
Habib Sammouda ◽  
Ali Belghith
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Natural Convection ◽  
Flow Structure ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Heat Fluxes ◽  
Complex Flow ◽  
Coupled Equations ◽  
Complex Flow Structure

The natural convection is studied in a cavity witch the lower half is filled with a porous media that is saturated with a first fluid (liquid), and the upper is filled with a second fluid (gas). The horizontal borders are heated and cooled by uniform heat fluxes and vertical ones are adiabatic. The formulation of the problem is based on the Darcy-Brinkman model. The density variation is taken into account by the Boussinesq approximation. The system of the coupled equations is resolved by the classic finite volume method. The numerical results show that the variation of the conductivity of the porous media influences strongly the flow structure and the heat transfer as well as in upper that in the lower zones. The effect of conductivity is conditioned by the porosity which plays a very significant roll on the heat transfer. The structures of this flow show that this kind of problem with specific boundary conditions generates a complex flow structure of several contra-rotating two to two cells, in the upper half of the cavity.

Transient Natural Convection of Water in a Horizontal Pipe With Constant Cooling Rate Through 4°C

1976 ◽  
Vol 98 (4) ◽  
pp. 581-587 ◽  
Author(s):  
K. C. Cheng ◽  
M. Takeuchi
Keyword(s):  
Natural Convection ◽  
Transient Flow ◽  
Temperature Fields ◽  
Freezing Process ◽  
Horizontal Pipe ◽  
Transfer Rates ◽  
Transient Natural Convection ◽  
Anomalous Density ◽  
Horizontal Cylinders ◽  
Relationship Of

A theoretical analysis is carried out to study the influence of an anomalous density-temperature relationship of water on the transient natural convection in horizontal cylinders with wall temperature decreasing at a uniform rate. Numercial solutions are obtained for three cases involving different cooling rates, pipe diameters, and initial uniform water temperatures for temperature conditions between 0 and 7°C. The transient flow and temperature fields, and local and overall heat transfer rates are presented to study the inversion of flow patterns caused by the maximum density at 4°C. The numerical results are compared with the experimental measurements and predictions of a quasi-steady boundary-layer model reported by Gilpin [2], and generally a good agreement is observed. Some implications on the subsequent freezing process are pointed out.

THE PRESSURE-INDUCED ROTATIONAL ABSORPTION SPECTRUM OF HYDROGEN: II. ANALYSIS OF THE ABSORPTION PROFILES

1959 ◽  
Vol 37 (11) ◽  
pp. 1249-1259 ◽  
Author(s):  
Z. J. Kiss ◽  
H. L. Welsh
Keyword(s):  
Experimental Data ◽  
Absorption Spectrum ◽  
Semiempirical Method ◽  
Density Variation ◽  
Rare Gases ◽  
Anomalous Density ◽  
Order Of Magnitude ◽  
Rotational Parts ◽  
Boltzmann Law ◽  
Dispersion Line

The experimental profiles obtained in Part I for the pressure-induced absorption of H2 and H2 – foreign gas mixtures in the region 300–1400 cm−1 are separated by a semiempirical method into rotational and translational parts. The pressure-induced rotational lines of H2 are shown to have a dispersion line shape, modified by the Boltzmann law. The intensities of the rotational parts of the spectra are, on the average, 13% greater than those calculated in Part I on the assumption of quadrupole interaction alone; the residual experimental intensity probably represents the effect of overlap interaction. The intensities of the translational parts of the spectra are of the same order of magnitude as the translational intensities in mixtures of the rare gases. Some additional experimental data on double rotational transitions and on the anomalous density variation of the absorption in H2–Xe mixtures are given.

Numerical simulation of natural convection using unsteady compressible Navier-stokes equations

2017 ◽  
Vol 27 (11) ◽  
pp. 2508-2527 ◽  
Author(s):  
Mahmoud M. El-Gendi ◽  
Abdelraheem M. Aly
Keyword(s):  
Natural Convection ◽  
Temperature Difference ◽  
Stokes Equations ◽  
Calculated Data ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Navier Stokes ◽  
Large Temperature ◽  
Present Calculation ◽  
Content Type

Purpose Boussinesq approximation is widely used in solving natural convection problems, but it has severe practical limitations. Using Boussinesq approximation, the temperature difference should be less than 28.6 K. The purpose of this study is to get rid of Boussinesq approximation and simulates the natural convection problems using an unsteady compressible Navier-Stokes solver. The gravity force is included in the source term. Three temperature differences are used namely 20 K, 700 K and 2000 K. Design/methodology/approach The calculations are carried out on the square and sinusoidal cavities. The results of low temperature difference have good agreement with the experimental and previous calculated data. It is found that, the high temperature difference has a significant effect on the density. Findings Due to mass conservation, the density variation affects the velocity distribution and its symmetry. On the other hand, the density variation has a negligible effect on the temperature distribution. Originality/value The present calculation method has no limitations but its convergence is slow. The current study can be used in fluid flow simulations for nuclear power applications in natural convection flows subjected to large temperature differences.

Anomalous density dependence of the v1 band of carbon dioxide in pressure-induced absorption

1970 ◽  
Vol 48 (1) ◽  
pp. 95-98 ◽  
Author(s):  
L. Mannik ◽  
A. R. W. McKellar ◽  
N. Rich ◽  
J. C. Stryland
Keyword(s):  
Carbon Dioxide ◽  
Density Dependence ◽  
Density Variation ◽  
Linear Term ◽  
Density Region ◽  
Induced Absorption ◽  
Active Absorption ◽  
Anomalous Density ◽  
Density Expansion

The anomaly in the density variation of the integrated absorption of the pressure-induced v1 band of carbon dioxide is shown experimentally to be represented by a linear term in the density expansion of the intensity, which is important only in the lower density region (0–20 amagat). A calculation indicates that the linear term arises from the infrared-active absorption of the v1 band of C16O18O.

Natural Convection in Cylindrical Configuration: Effect of the Obstacle on the Unsteadiness

2002 ◽  
Author(s):  
K. Choukairy ◽  
R. Bennacer ◽  
P. D. Matthey ◽  
R. Duval
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Molecular Diffusion ◽  
Control Volume ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Necessary Condition ◽  
Thermal Transfer ◽  
The One ◽  
Control Volume Approach

The heat transfer by natural convection are frequently used in the various processes and are also met in various situation in nature. In order to improve these kind of heat transfer, it’s possible to disturb the flow of origin by an obstacle along the way of the principal flow. This obstacle modifies on the one hand the structure of the flow and affects the local transfers. On the other hand, it allows the transition towards and obtaining a macroscopic contribution (eddy) in complement of the microscopic transfer (molecular diffusion). The effect of an obstacle on the thermal transfer, was previously studied and we purpose to complete such studies in transitional domain. The obtained non-stationary natural convection is analysed. A study is carried out by considering the transient resolution (DNS) of such problem in two-dimensional configuration. The density variation is taken into account by the boussinesq approximation. The control-volume approach is used for solving the governing equation. The temporal variation of Nusselt and energy is given with and without obstacle. We illustrate the necessary condition in order to improve the transfer in such configuration. The effect of height and width of the inserted body is systematically analysed.

Non-linear natural convection and mass transfer flow near a vertical moving porous plate with chemical reaction and Soret effect

2019 ◽  
Vol 15 (5) ◽  
pp. 846-858 ◽  
Author(s):  
Basant Kumar Jha ◽  
Muhammad Nasir Sarki
Keyword(s):  
Natural Convection ◽  
Skin Friction ◽  
Thermal Diffusion ◽  
Chemical Reaction ◽  
Soret Effect ◽  
Porous Plate ◽  
Density Variation ◽  
Content Type ◽  
Non Linear ◽  
Transfer Flow

Purpose The purpose of this paper is to conduct a theoretical study on steady fully developed non-linear natural convection and mass transfer flow past an infinite vertical moving porous plate with chemical reaction and thermal diffusion effect. Closed-form expressions for dimensionless velocity, concentration, Sherwood number and skin-friction are obtained by solving the present mathematical model. Design/methodology/approach The fully developed steady non-linear natural convection and mass transfer flow near a vertical moving porous plate with chemical reaction and thermal diffusion effect is investigated. The non-linear density variation and Soret effect were taken into consideration. The dimensionless velocity, temperature and concentration profiles were obtained in terms of exponential functions, and were used to compute the governing parameters, skin-friction and Sherwood number. Findings The effect of coefficient of the non-linear density variation with the temperature (NDT) and concentration (NDC) parameter, chemical reaction parameter, thermal diffusion parameter are discussed with the aid of line graphs and tables. The analysis of the result shows that the velocity as well as skin-friction having higher values in the case of non-linear variation of density with temperature and concentration in comparison to linear variation of density with temperature and concentration. It is observed that the velocity and skin-friction increase with an increase in the Soret parameter. Originality/value The aim of this paper is to extend the work of Muthucumaraswamy (2002) by incorporating the thermal diffusion (Soret) effect and non-linear density variation with temperature (NDT) and concentration (NDC), on which, to the best knowledge of the authors, no studies have been carried out.

Fluid-structural dynamics of ground-based and microgravity caloric tests

2005 ◽  
Vol 15 (2) ◽  
pp. 93-107
Author(s):  
M. Kassemi ◽  
J.G. Oas ◽  
Dimitri Deserranno
Keyword(s):  
Natural Convection ◽  
Driving Forces ◽  
Density Variation ◽  
Microgravity Environment ◽  
Bulk Fluid ◽  
Basic Premise ◽  
Caloric Stimulation ◽  
The Impact ◽  
Orbiting Spacecraft ◽  
Caloric Tests

Microgravity caloric tests aboard the 1983 SpaceLab1 mission produced nystagmus results with an intensity comparable to those elicited during post- and pre- flight tests, thus contradicting the basic premise of Barany's convection hypothesis for caloric stimulation. In this work, we present a dynamic fluid structural analysis of the caloric stimulation of the lateral semicircular canal based on two simultaneous driving forces for the endolymphatic flow: natural convection driven by the temperature-dependent density variation in the bulk fluid and expansive convection caused by direct volumetric displacement of the endolymph during the thermal irrigation. Direct numerical simulations indicate that on earth, the natural convection mechanism is dominant. But in the microgravity environment of orbiting spacecraft, where buoyancy effects are mitigated, expansive convection becomes the sole mechanism for producing cupular displacement. A series of transient 1 g and microgravity case studies are presented to delineate the differences between the dynamics of the 1 g and microgravity endolymphatic flows. The impact of these different flow dynamics on the endolymph-cupula fluid-structural interactions is also analyzed based on the time evolutions of cupular displacement and velocity and the transcupular pressure differences.

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