Heat thermal structure in the interfacial boundary layer measured in an open tank of water in turbulent free convection

1977 ◽  
Vol 83 (2) ◽  
pp. 311-335 ◽  
Author(s):  
Kristina B. Katsaros ◽  
W. Timothy Liu ◽  
Joost A. Businger ◽  
James E. Tillman
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Standard Deviation ◽  
Theoretical Calculations ◽  
Thermal Structure ◽  
The Body ◽  
Heat Diffusion ◽  
Return Flow ◽  
Experimental Conditions ◽  
Heat Diffusion Equation

The thermal structure in the boundary layer and its relation to the heat flux from the cooling and evaporating surface of a deep tank of water are investigated. When a deep layer of water in contact with still air above loses heat to the air, the cooled water in a region just under the surface converges along lines and then plunges down in sheets. These sheets of falling water dissipate as they move into the body of the water, which is in turbulent motion. The vertical profiles of the horizontally averaged temperature and its standard deviation agree fairly closely with theoretical profiles based on time averages of the solution to the heat diffusion equation. The differences between observed and thus predicted profile shapes are consistent with the expected effects of the falling cold thermals and the warm return flow, which are neglected in the theories. The profiles of the standard deviation have large values up to the interface and lie between predictions based on boundary conditions of constant surface temperature and constant heat flux, in keeping with the experimental conditions.The relation between the net heat flux and the temperature difference across the boundary layer is given in non-dimensional form by N = 0[sdot ]156R0[sdot ]33, which is in good agreement with the asymptotic similarity prediction N [vprop ] R1/3 but lower than theoretical calculations of the upper bound of N vs. R.

Thermally induced mineral and chemical transformations in calcareous mudstones around a basaltic dyke (Perthus Pass, southern Massif Central, France). Possible implications as a natural analogue of nuclear waste disposal

Clay Minerals ◽  
2007 ◽  
Vol 42 (2) ◽  
pp. 213-231 ◽  
Author(s):  
C. Henry ◽  
J.-Y. Boisson ◽  
A. Bouchet ◽  
A. Meunier
Keyword(s):  
Theoretical Calculations ◽  
Heat Diffusion ◽  
Large Temperature ◽  
Chemical Transformations ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Retention Capacity ◽  
Massif Central ◽  
Thermally Induced ◽  
X Ray

AbstractA mixed-layer illite-smectite, illite-rich calcareous mudstone intruded by a basaltic dyke at the Perthus Pass (southern Massif Central, France) allows us to study the transformation of clays subjected to a brief thermal gradient. X-ray diffraction, scanning electron microscopy, electron microprobe and atomic absorption spectroscopy analyses were performed on samples at variable distances from the mudstone-dyke contacts.A roughly similar evolution is seen on both sides of the dyke: quartz, calcite, kaolinite and illite disappear; Ca-silicates, albite and saponite-beidellite form, late meteoric halloysite crystallizes in open fractures.Chemical and mineralogical transformations are related to heat diffusion from the dyke. Theoretical calculations highlight the influence of the dyke orientation. The mineralogical reactions observed in rocks are similar to those observed in experimental conditions. The formation of new swelling phases with a high retention capacity linked to a short duration, large-temperature increase, should constitute a positive process for Repository Performance Assessment.

A Hybrid Heat Flux Distribution Model for Jet Impingment on a Flat Plate

2008 ◽  
Author(s):  
Gerardo Carbajal ◽  
G. P. Peterson ◽  
C. B. Sobhan ◽  
D. T. Queheillalt
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Flux Distribution ◽  
Heat Diffusion ◽  
Aluminum Plate ◽  
Back Side ◽  
Heat Flux Distribution ◽  
Heat Diffusion Equation ◽  
Parabolic Function ◽  
Probabilistic Function

A hybrid numerical-experimental technique has been developed to determine the unknown non-uniform heat flux distribution produced by the impingement of a jet on one side of a vertical flat aluminum plate. The method involves coupling of the unknown heat flux distribution as a boundary condition to the heat diffusion equation, which is solved by the finite volume method utilizing a computer code developed for the purpose. The heat flux distribution has been modeled using both a deterministic parabolic function and a probabilistic function. The resulting transient inverse problem was solved by comparing the numerical solution with the experimental data on the back side of the plate. In the experimental method, the aluminum plate was heated for 40 seconds, and an infrared camera located at the back side was used to record the transient temperature data at intervals of one second. A propane torch was the source of the impinging jet, with the flux intensity assumed to be constant with respect to time. The solid plate was cooled by natural convection and radiation heat transfer at the back side. It was found that use of the probabilistic function for the heat flux distribution produced numerical results where the temperature difference between the numerical and experimental data was within an error limit of 0.4 °C. Conversely, the parabolic function produced temperature results that did not match well with the experimental data.

Fractional-Diffusion Solutions for Transient Local Temperature and Heat Flux

1999 ◽  
Vol 122 (2) ◽  
pp. 372-376 ◽  
Author(s):  
V. V. Kulish ◽  
J. L. Lage
Keyword(s):  
Heat Flux ◽  
Diffusion Equation ◽  
Local Time ◽  
Simple Relation ◽  
Solution Procedure ◽  
Heat Diffusion ◽  
Time Varying ◽  
Infinite Domain ◽  
Heat Diffusion Equation ◽  
Transient Heat Diffusion

Applying properties of the Laplace transform, the transient heat diffusion equation can be transformed into a fractional (extraordinary) differential equation. This equation can then be modified, using the Fourier Law, into a unique expression relating the local value of the time-varying temperature (or heat flux) and the corresponding transient heat flux (or temperature). We demonstrate that the transformation into a fractional equation requires the assumption of unidirectional heat transport through a semi-infinite domain. Even considering this limitation, the transformed equation leads to a very simple relation between local time-varying temperature and heat flux. When applied along the boundary of the domain, the analytical expression determines the local time-variation of surface temperature (or heat flux) without having to solve the diffusion equation within the entire domain. The simplicity of the solution procedure, together with some introductory concepts of fractional derivatives, is highlighted considering some transient heat transfer problems with known analytical solutions. [S0022-1481(00)01002-1]

The Impact of Horizontal Model Grid Resolution on the Boundary Layer Structure over an Idealized Valley

2014 ◽  
Vol 142 (9) ◽  
pp. 3446-3465 ◽  
Author(s):  
Johannes S. Wagner ◽  
Alexander Gohm ◽  
Mathias W. Rotach
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Layer Structure ◽  
Thermal Structure ◽  
Inversion Layer ◽  
Lower Boundary ◽  
Grid Resolution ◽  
Convective Boundary ◽  
Boundary Layer Structure ◽  
The Impact

The role of horizontal model grid resolution on the development of the daytime boundary layer over mountainous terrain is studied. A simple idealized valley topography with a cross-valley width of 20 km, a valley depth of 1.5 km, and a constant surface heat flux forcing is used to generate upslope flows in a warming valley boundary layer. The goal of this study is to investigate differences in the boundary layer structure of the valley when its topography is either fully resolved, smoothed, or not resolved by the numerical model. This is done by performing both large-eddy (LES) and kilometer-scale simulations with horizontal mesh sizes of 50, 1000, 2000, 4000, 5000, and 10 000 m. In LES mode a valley inversion layer develops, which separates two vertically stacked circulation cells in an upper and lower boundary layer. These structures weaken with decreasing horizontal model grid resolution and change to a convective boundary layer over an elevated plain when the valley is no longer resolved. Mean profiles of the LES run, which are obtained by horizontal averaging over the valley show a three-layer thermal structure and a secondary heat flux maximum at ridge height. Strong smoothing of the valley topography prevents the development of a valley inversion layer with stacked circulation cells and leads to higher valley temperatures due to smaller valley volumes. Additional LES and “1 km” runs over corresponding smoothed valleys reveal that differences occur mainly because of unresolved topography and not because of unresolved turbulence processes. Furthermore, the deactivation of horizontal diffusion improved simulations with 1- and 2-km horizontal resolution.

Relative Intensities in ED Patterns From Thin Gold Films

1972 ◽  
Vol 30 ◽  
pp. 636-637
Author(s):  
R. H. Morriss ◽  
J. D. C. Peng ◽  
C. D. Melvin
Keyword(s):  
Theoretical Calculations ◽  
Diffraction Theory ◽  
Gold Films ◽  
Reasonable Accuracy ◽  
Experimental Conditions ◽  
Crystal Perfection ◽  
Heavy Atoms ◽  
Fine Focus ◽  
Convergent Beam ◽  
Beam Diffraction

Although dynamical diffraction theory was modified for electrons by Bethe in 1928, relatively few calculations have been carried out because of computational difficulties. Even fewer attempts have been made to correlate experimental data with theoretical calculations. The experimental conditions are indeed stringent - not only is a knowledge of crystal perfection, morphology, and orientation necessary, but other factors such as specimen contamination are important and must be carefully controlled. The experimental method of fine-focus convergent-beam electron diffraction has been successfully applied by Goodman and Lehmpfuhl to single crystals of MgO containing light atoms and more recently by Lynch to single crystalline (111) gold films which contain heavy atoms. In both experiments intensity distributions were calculated using the multislice method of n-beam diffraction theory. In order to obtain reasonable accuracy Lynch found it necessary to include 139 beams in the calculations for gold with all but 43 corresponding to beams out of the [111] zone.

Men’s Hunger, Food Consumption, and Preferences for Female Body Types

2014 ◽  
Vol 45 (6) ◽  
pp. 495-497 ◽  
Author(s):  
Nicolas Guéguen
Keyword(s):  
Food Consumption ◽  
Female Body ◽  
The Body ◽  
Slender Body ◽  
Mediation Effect ◽  
Point Scale ◽  
Body Type ◽  
Experimental Conditions

Nelson and Morrison (2005 , study 3) reported that men who feel hungry preferred heavier women. The present study replicates these results by using real photographs of women and examines the mediation effect of hunger scores. Men were solicited while entering or leaving a restaurant and asked to report their hunger on a 10-point scale. Afterwards, they were presented with three photographs of a woman in a bikini: One with a slim body type, one with a slender body type, and one with a slightly chubby body. The participants were asked to indicate their preference. Results showed that the participants entering the restaurant preferred the chubby body type more while satiated men preferred the thinner or slender body types. It was also found that the relation between experimental conditions and the choices of the body type was mediated by men’s hunger scores.

Determination of alcohols in mixtures by 19F NMR spectroscopy using hexefluoroacetone reagent

1982 ◽  
Vol 47 (7) ◽  
pp. 1973-1978 ◽  
Author(s):  
Jiří Karhan ◽  
Zbyněk Ksandr ◽  
Jiřina Vlková ◽  
Věra Špatná
Keyword(s):  
Standard Deviation ◽  
Nmr Spectroscopy ◽  
Standard Method ◽  
Internal Standard ◽  
Internal Standard Method ◽  
Concentration Region ◽  
Experimental Conditions ◽  
Curve Method ◽  
Sample Preparation Procedure

The determination of alcohols by 19F NMR spectroscopy making use of their reaction with hexafluoroacetone giving rise to hemiacetals was studied on butanols. The calibration curve method and the internal standard method were used and the results were mutually compared. The effects of some experimental conditions, viz. the sample preparation procedure, concentration, spectrometer setting, and electronic integration, were investigated; the conditions, particularly the concentrations, proved to have a statistically significant effect on the results of determination. For the internal standard method, the standard deviation was 0.061 in the concentration region 0.032-0.74 mol l-1. The method was applied to a determination of alcohols in the distillation residue from an oxo synthesis.

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