Specific heat of ordered and isotopically disordered lattices

1978 ◽  
Vol 56 (10) ◽  
pp. 1390-1394
Author(s):  
K. P. Srivastava
Keyword(s):  
Specific Heat ◽  
Low Temperatures ◽  
Numerical Study ◽  
Three Dimensional ◽  
Constant Volume ◽  
Nearest Neighbour ◽  
Two Dimensional ◽  
Appreciable Difference ◽  
Substantial Change ◽  
Neighbour Interaction

An extensive numerical study on specific heat at constant volume (Cv) for ordered and isotopically disordered lattices has been made. Cv at various temperatures for ordered and disordered linear and two-dimensional lattices have been compared and no appreciable difference in Cv between these two structures has been observed. Effect of concentration of light atoms on Cv for three-dimensional isotopically disordered lattices has also been shown.In spite of taking next-nearest-neighbour interaction into account, no substantial change in Cv between the ordered and isotopically disordered linear lattices has been found. It is shown that the low lying modes contribute substantially at low temperatures.

Numerical Study of Flow and Heat Transfer Characteristics of Impinging Jets

2010 ◽  
Author(s):  
Tarek M. Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

This study presents results for flow and heat transfer characteristics of two-dimensional rectangular impinging jets and three-dimensional circular impinging jets. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume computational fluid dynamics (CFD) code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results of the three-dimensional cases show that Reynolds number has no effect on the velocity distribution of the center jet. Results of both two-dimensional and three-dimensional cases show that Reynolds number highly affects the heat transfer and values of the Nusselt number. The maximum Nusselt number was always found at the stagnation point of the center jet.

scholarly journals Three-dimensional stability of a horizontally sheared flow in a stably stratified fluid

2007 ◽  
Vol 570 ◽  
pp. 297-305 ◽  
Author(s):  
AXEL DELONCLE ◽  
JEAN-MARC CHOMAZ ◽  
PAUL BILLANT
Keyword(s):  
Froude Number ◽  
Dimensional Stability ◽  
Numerical Study ◽  
Three Dimensional ◽  
Stratified Fluid ◽  
Two Dimensional ◽  
Horizontal Shear ◽  
Homogeneous Fluid ◽  
Sheared Flow ◽  
Vertical Scales

This paper investigates the three-dimensional stability of a horizontal flow sheared horizontally, the hyperbolic tangent velocity profile, in a stably stratified fluid. In an homogeneous fluid, the Squire theorem states that the most unstable perturbation is two-dimensional. When the flow is stably stratified, this theorem does not apply and we have performed a numerical study to investigate the three-dimensional stability characteristics of the flow. When the Froude number, Fh, is varied from ∞ to 0.05, the most unstable mode remains two-dimensional. However, the range of unstable vertical wavenumbers widens proportionally to the inverse of the Froude number for Fh ≪ 1. This means that the stronger the stratification, the smaller the vertical scales that can be destabilized. This loss of selectivity of the two-dimensional mode in horizontal shear flows stratified vertically may explain the layering observed numerically and experimentally.

Critical Phenomena at the Antiferromagnetic Transition in MnO

1999 ◽  
Vol 602 ◽  
Author(s):  
B.F. Woodfield ◽  
J.L. Shapiro ◽  
R. Stevens ◽  
J. Boerio-Goates ◽  
M.L. Wilson
Keyword(s):  
Ising Model ◽  
Critical Exponent ◽  
Specific Heat ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Applied Pressure ◽  
Polycrystalline Sample ◽  
Type Ii ◽  
Two Dimensional ◽  
Antiferromagnetic Transition

AbstractThe specific heat of a polycrystalline sample of MnO was measured from T ≈ 1 K to T ≈ 400 K using two different experimental apparatuses at zero applied pressure. Features revealed by the data include a hyperfine contribution due to the Mn nuclei, a T2 temperature dependence at low temperatures due to the type-II antiferromagnetic magnon contribution, and a sharp but well defined antiferromagnetic transition (TN = 117.7095 K) that is clearly second order in nature. The critical exponent, α, deduced from the transition is consistent with a two dimensional Ising model. The specific heat of MnO is also compared with recent results on the type-A antiferromagnet LaMnO3.

Statistical mechanics of the two-dimensional assembly

1950 ◽  
Vol 202 (1069) ◽  
pp. 202-207 ◽  
Keyword(s):  
Ising Model ◽  
Curie Temperature ◽  
Statistical Mechanics ◽  
Specific Heat ◽  
Considerable Effect ◽  
Square Lattice ◽  
Nearest Neighbour ◽  
Two Dimensional ◽  
Triangular Lattices

The work of Kaufman & Onsager (1946) on the two-dimensional Ising model of a ferromagnet is extended from the plane square lattice to the plane honeycomb and triangular lattices. The specific heat anomaly, where it exists, turns out to be of the same type in all three lattices, an infinity in the specific heat at the Curie temperature. It is concluded that second-nearest neighbour interactions may have a considerable effect on the position of the Curie temperature.

Numerical Study of the Turbulent Wake of a Towed or Auto-Propelled Axisymmetrical Body in a Stratified Medium Using LES-VMS

2013 ◽  
Author(s):  
B. Sainte-Rose ◽  
X. Lenhardt ◽  
O. Allain ◽  
A. Dervieux
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Turbulent Wake ◽  
Flow Dynamics ◽  
Stratified Medium ◽  
Two Dimensional ◽  
Multi Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Good Agreement

Numerical simulations of close and far wakes behind an axisymmetrical body in a stratified medium are carried out. Towed and auto-propelled regimes are considered. The parameters of the flow are Pr = 7, Re = 10000 based on the diameter of the cylinder and F = 25. Turbulence is modelled with a Large Eddy Simulation - Variational Multi-Scale approach. Realistic results are obtained for the towed case where the so-called three-dimensional (3D), non-equilibrium (NEQ) and quasi two-dimensional (Q2D) regimes are exhibited with very good agreement with the experiments. In addition, the effect of auto-propulsion on the flow dynamics is satisfactorily addressed.

scholarly journals A Numerical Study of the effect of Bolt Thread Geometry on the Load Distribution of Continuous Threads

2021 ◽  
Author(s):  
Abdulla Sherif Mahmoud Fathalla ◽  
◽  
Ali Akhavan Farid ◽  
Reza Moezzi ◽  
Seyed Saeid Rahimian Koloor ◽  
...  
Keyword(s):  
Load Distribution ◽  
Numerical Study ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Reliable Performance ◽  
Dimensional Simulation ◽  
Three Dimensional Finite Element ◽  
Distribution Behaviour

Load distribution has been studied extensively for ISO thread, but the load distribution on power screw threads, specifically ACME and Square threads, has not been studied yet. In this article, axisymmetric two-dimensional and three-dimensional Finite Element Analysis have been conducted on bolts with different sizes and thread geometries to examine the effect of the thread geometry on the load distribution. The thread geometries were studied with ISO, ACME, and Square threads attention. The sizes used are from the ISO coarse series. In order to investigate on the effect of bolt thread geometry, several simulations have been performed. The two-dimensional simulation results have shown reliable performance in determining the load distribution behaviour when the thread geometry is modified. Moreover, the results agreed with the three-dimensional simulation outcomes regarding the load distribution behaviour when the size is varied.

Unsteady flow of gas at high pressure into a closed volume filled with liquid

2020 ◽  
Vol 6 (4) ◽  
pp. 127-140
Author(s):  
Maksim V. Alekseev ◽  
Ivan S. Vozhakov ◽  
Sergey I. Lezhnin
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Water System ◽  
Liquid Lead ◽  
Asymptotic Model ◽  
Closed Volume ◽  
Two Dimensional ◽  
Open Platform ◽  
Significant Difference ◽  
The One

Within the framework of 2D (two-dimensional, axisymmetric) and 3D (three-dimensional) formulations of the problem, this article presents a numerical simulation of the process of gas outflow under pressure into a closed container partially filled with liquid. The authors have performed the numerical modeling using the open platform OpenFOAM with the help of a solver based on the method of liquid volumes (VOF method) with a standard k-e turbulence model. A comparison is made with the one-dimensional (1D) asymptotic model, in which the oscillations of the fluid as a whole are determined by the enthalpy balance. A numerical study of the evolution of pressure during gas outflow is carried out. The results show that the physical properties of the fluid used affect the amplitude and frequency of the pulsations. The modeling has shown that gas flows into water in the form of a jet, and a projectile forms in liquid lead near the hole through which it flows out. The significant influence of three-dimensional effects on the evolution of gas outflow into liquid is demonstrated. Satisfactory agreement was obtained for both two-dimensional and three-dimensional calculations and the results obtained using the asymptotic model. For the “gas — water” system, the results of calculations by the asymptotic model give a significant difference from the results of numerical calculations.

scholarly journals Numerical study of an ion-exchanged glass waveguide using both two-dimensional and three-dimensional models

2011 ◽  
Vol 43 (4) ◽  
pp. 882-888 ◽  
Author(s):  
Pengfei Wang ◽  
Yuliya Semenova ◽  
Jie Zheng ◽  
Qiang Wu ◽  
Agus Muhamad Hatta ◽  
...  
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Glass Waveguide
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