The thermal bar

1992 ◽  
Vol 236 ◽  
pp. 27-42 ◽  
Author(s):  
S. S. Zilitinkevich ◽  
K. D. Kreiman ◽  
A. Yu. Terzhevik
Keyword(s):  
Laboratory Experiments ◽  
Heat Budget ◽  
Traditional Approach ◽  
Laminar Regime ◽  
Laboratory Measurements ◽  
Cold Zone ◽  
Thermal Bar ◽  
Simple Theoretical Model ◽  
Theoretical Predictions ◽  
Zone Ii

A simple theoretical model of the thermal bar is derived on the basis of heat budget equations for the following three zones of a wedge-shaped water basin warmed from above: (i) stably stratified shallow warm-water zone; (ii) vicinity of the bar; (iii) convectively mixed deep cold zone. In contrast to the traditional approach, advective warming of the vicinity of the bar and associated facilitating of the thermal bar propagation are taken into account. Theoretical predictions are compared with the data of lacustrine and laboratory measurements taken from current literature. New laboratory experiments have been carried out to examine the laminar regime of the thermal bar.

scholarly journals A Theoretical Model of Thermal Bar Movement in a Circular Lake

1993 ◽  
Vol 24 (1) ◽  
pp. 13-30 ◽  
Author(s):  
S. S. Zilitinkevich ◽  
J. G. B. Malm
Keyword(s):  
Theoretical Model ◽  
Field Data ◽  
Present Model ◽  
Heat Budget ◽  
Maximum Density ◽  
Thermal Bar ◽  
Simple Theoretical Model ◽  
Model Predictions ◽  
Budget Equation ◽  
Infinite Wedge

The present paper concentrates on the movement of the spring thermal bar with time, and a simple theoretical model is derived for the case of an axisymmetric circular lake. The lake is considered to consist of three different zones: 1) a nearshore stably stratified warm water zone, 2) the thermal bar zone of descending water with temperature approximately equal to that of maximum density, and 3) an offshore cold unstably stratified zone. The basis for the model is the heat budget equation, where horizontal dynamical heat exchange in the vicinity of the bar zone is taken into account. In comparison with a previous model (Zilitinkevich et al. 1991), describing an infinite wedge of water, the present model is more general and takes into account the effect of shore-line curvature. This effect is characterized by a non-dimensional number and causes a marked increase in the displacement rate of the bar at the final stage of its existence. Model predictions are also compared with field data taken from the literature.

Plasma Jet Ignition of Methanol at Sub-Zero Temperatures

1994 ◽  
Vol 208 (3) ◽  
pp. 153-159 ◽  
Author(s):  
J R Dawe ◽  
P R Smy ◽  
R F Haley ◽  
J D Dale ◽  
M F Bardon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Laboratory Experiments ◽  
Plane Surface ◽  
Plasma Jet ◽  
Pulsed Plasma ◽  
Test Liquid ◽  
Cold Starting ◽  
Simple Theoretical Model ◽  
Sufficient Energy ◽  
Fuel Vaporization

Use of a pulsed plasma jet igniter to improve low-temperature starting of 100 per cent methanol (M100) fuelled engines is explored. A simple theoretical model of heat transfer from plasma to liquid methanol shows that sufficient energy is transferred for fuel vaporization in cold starting. Two laboratory experiments test liquid plane surface and droplet modes of ignition. An ordinary four cylinder auto engine fitted with plasma jet igniters is tested for cold starting in a Canadian winter, and cold starting is improved from +10°C (conventional ignition) to −16°C.

The influence of nonlinear bottom friction on the properties of decaying cyclonic and anticyclonic vortex structures in a shallow rotated fluid

2014 ◽  
Vol 753 ◽  
pp. 217-241 ◽  
Author(s):  
S. V. Kostrykin ◽  
A. A. Khapaev ◽  
I. G. Yakushkin
Keyword(s):  
Horizontal Plane ◽  
Laboratory Experiments ◽  
Initial State ◽  
Turbulent Eddy ◽  
Modified Model ◽  
Initial Stage ◽  
Free Decay ◽  
Axisymmetric Vortex ◽  
Theoretical Predictions ◽  
Eddy Flow

AbstractThe problem of the decay of intense vortices in a shallow rotated neutrally stratified fluid is considered using simulations with a modified model of von Kármán type and laboratory experiments. The numerical model describes a forced axisymmetric vortex, vertically confined, but infinite in the horizontal plane. It may be used for comparisons with laboratory experiments, in which a quasi-turbulent eddy flow is generated, using magnetohydrodynamic forcing. A detailed analysis of simulations of the free decay of the flow from an initial state, given either by an arbitrary Poiseuille or by a forced stationary profile of vorticity, is provided. Based on this analysis, three different regimes of decay of intense anticyclones in the parameter space of the Ekman and initial Rossby numbers are found. It is shown that anticyclones with large enough Rossby and small enough Ekman numbers may decay to a non-trivial stationary state, or at least they decay much slower than cyclones of the same intensity. The laboratory experiments show much slower decay of intense anticyclones than weak anticyclones or cyclones, and also a dominance of anticyclones over cyclones during the initial stage of decay. These observations qualitatively agree with theoretical predictions.

Magnetic dipole rotation spectrum of oxygen

1969 ◽  
Vol 310 (1503) ◽  
pp. 579-590 ◽  
Keyword(s):  
Magnetic Dipole ◽  
Spectral Range ◽  
Experimental Error ◽  
Quantitative Comparison ◽  
Laboratory Measurements ◽  
Signal Noise ◽  
Theoretical Predictions ◽  
Noise Ratio ◽  
Rotation Spectrum ◽  
Line Strengths

The identification of the magnetic dipole rotation spectrum of oxygen in atmospheric studies has been confirmed by laboratory measurements in the spectral range 12 to 65 cm -1 , using interferometric techniques combined with long absorption paths and pressures of 2 to 3 atmospheres. A quantitative comparison has also been made between the laboratory observations and the theoretical predictions, giving agreement in the frequencies to within +0∙026 cm -1 and that of the integrated line-strengths within experimental error, as defined by the signal/noise ratio of the observed spectra.

scholarly journals Modeling of Screw-Dental Structure Interaction: First Step Toward Finite Element Analysis

2020 ◽  
Vol 23 (2) ◽  
pp. 125-129
Author(s):  
A. Pasculli ◽  
F. Rizzo ◽  
M. Mangifesta ◽  
A. Viskovic ◽  
A. De Sanctis ◽  
...  
Keyword(s):  
Finite Element ◽  
Error Propagation ◽  
Laboratory Experiments ◽  
Fragility Curves ◽  
Laboratory Measurements ◽  
Research Activity ◽  
Element Analysis ◽  
Support Materials ◽  
Structure Interaction ◽  
Error Propagation Analysis

This research is focused on the screw-structure interaction under dynamic impulses aimed to the contact analysis of gap propagation at dental implant-abutment interface under dynamic loading. The purpose is to investigate the fracture mechanism that occurs during the screw penetration in a support and during the support vibration. Numerical Finite Element (FEM) analyses are calibrated through experimental laboratory measurements on support materials and screws typologies. Uncertainty due to the laboratory error propagation is investigated using Polynomial Chaos Expansion (PCE) of experimental measurements. The research is planned through the following steps: FEM calibration trough laboratory experiments on materials; laboratory experiments and material mechanics identification; uncertainty error propagation analysis through PCE expansion; fragility curves for numerical model calibration; FEM models calibration trough laboratory measurements on cycling loads. Therefore, the main purpose of the research activity, of which this article constitutes a preliminary and an explorative step, is to study a methodology that minimizes the local damage of the dental material due to the generation of micro-cracks following the implantation actions. Accordingly, in this paper, preliminary results are reported.

scholarly journals Laboratory measurements of stomatal NO<sub>2</sub> deposition to native California trees and the role of forests in the NO<sub><i>x</i></sub> cycle

2020 ◽  
Author(s):  
Erin R. Delaria ◽  
Bryan K. Place ◽  
Amy X. Liu ◽  
Ronald C. Cohen
Keyword(s):  
Laboratory Experiments ◽  
Field Measurements ◽  
Large Degree ◽  
Laboratory Studies ◽  
Laboratory Measurements ◽  
Deposition Fluxes ◽  
Deposition Velocities ◽  
Direct Laser ◽  
Leaf Level

Abstract. Both canopy-level field measurements and laboratory studies suggest that absorption of NO2 through the leaf stomata of vegetation is a significant sink of atmospheric NOx. However, the mechanisms of this foliar NO2 uptake and their impact on NOx lifetimes remains incompletely understood. To understand the leaf-level processes affecting ecosystem scale atmosphere-biosphere NOx exchange, we have conducted laboratory experiments of branch-level NO2 deposition fluxes to six coniferous and four broadleaf native California trees using a branch enclosure system with direct Laser Induced Fluorescence (LIF) detection of NO2. We report NO2 foliar deposition that demonstrates a large degree of inter-species variability, with maximum observed deposition velocities ranging from 0.15–0.51 cm/s during the daytime, as well as significant stomatal opening during the night. We also find that the contribution of mesophyllic processing to the overall deposition rate of NO2 varies by tree species, but has an ultimately inconsequential impact on NOx budgets and lifetimes. Additionally, we find no evidence of any emission of NO2 from leaves, suggesting an effective uni-directional exchange of NOx between the atmosphere and vegetation.

The growth of compositionally stratified solid above a horizontal boundary

1989 ◽  
Vol 199 ◽  
pp. 29-53 ◽  
Author(s):  
Andrew W. Woods ◽  
Herbert E. Huppert
Keyword(s):  
Laboratory Experiments ◽  
Thermal Flux ◽  
Far Field ◽  
Diffusive Transport ◽  
Heavy Fluid ◽  
Heavy Component ◽  
Simple Theoretical Model ◽  
Fixed Composition ◽  
Composite Solid ◽  
Compositional Convection

The compositional stratification in solid formed by cooling a binary alloy from below is investigated theoretically and experimentally. It is shown that in order to grow composite solid the boundary temperature needs to be below the eutetic temperature. Two separate cases are considered. In the first, heavy fluid is released on solidification. The solid growth is then governed by the diffusive transport of heat and composition. The resultant solid is shown to have a fixed composition until the far-field conditions change. In the second case, light fluid is released on solidification. This generates turbulent compositional convection in the melt which significantly increases the transport of heat and composition across the solid/melt interface. As a result, the fraction of heavy component in the solid initially increases, but subsequently decreases to conserve mass. A simple theoretical model, using the approximation of a flat solid/melt interface is developed; this predicts differences in the thermal flux in saturated and undersaturated melts. Laboratory experiments involving aqueous solutions of sodium carbonate cooled from below which released light fluid displayed compositional convection and stratification of the solid as predicted.

scholarly journals Alpha-pinene oxidation by OH: simulations of laboratory experiments

2004 ◽  
Vol 4 (9/10) ◽  
pp. 2285-2311 ◽  
Author(s):  
M. Capouet ◽  
J. Peeters ◽  
B. Nozi`ere ◽  
J.-F. Müller
Keyword(s):  
Gas Phase ◽  
Laboratory Experiments ◽  
State Of The Art ◽  
Peroxy Radicals ◽  
Large Scatter ◽  
Laboratory Measurements ◽  
Model Simulations ◽  
Product Yields ◽  
Alpha Pinene ◽  
Primary Products

Abstract. This paper presents a state-of-the-art gas-phase mechanism for the degradation of α-pinene by OH and its validation by box model simulations of laboratory measurements. It is based on the near-explicit mechanisms for the oxidation of α-pinene and pinonaldehyde by OH proposed by Peeters and co-workers. The extensive set of α-pinene photooxidation experiments performed in presence as well as in absence of NO by Nozière et al. (1999a) is used to test the mechanism. The comparison of the calculated vs measured concentrations as a function of time shows that the levels of OH, NO, NO2 and light are well reproduced in the model. Noting the large scatter in the experimental results as well as the difficulty to retrieve true product yields from concentrations data, a methodology is proposed for comparing the model and the data. The model succeeds in reproducing the average apparent yields of pinonaldehyde, acetone, total nitrates and total PANs in the experiments performed in presence of NO. In absence of NO, pinonaldehyde is fairly well reproduced, but acetone is largely underestimated. The dependence of the product yields on the concentration of NO and α-pinene is investigated, with a special attention on the influence of the multiple competitions of reactions affecting the peroxy radicals in the mechanism. We show that the main oxidation channels differ largely according to photochemical conditions. E.g. the pinonaldehyde yield is estimated to be about 10% in the remote atmosphere and up to 60% in very polluted areas. We stress the need for additional theoretical/laboratory work to unravel the chemistry of the primary products as well as the ozonolysis and nitrate-initiated oxidation of α-pinene.

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