Inviscid quasi-geostrophic flow over topography: testing statistical mechanical theory

1996 ◽  
Vol 309 ◽  
pp. 85-91 ◽  
Author(s):  
William J. Merryfield ◽  
Greg Holloway
Keyword(s):  
Numerical Simulations ◽  
Large Range ◽  
Initial Conditions ◽  
Steady Flows ◽  
Mechanical Theory ◽  
Geostrophic Flow ◽  
Mechanical Description ◽  
Flow Over Topography ◽  
Statistical Mechanical ◽  
Parameter Values

Numerical simulations are employed in a detailed test of the statistical mechanical description of topographic turbulence. Predictions of steady flows correlated with topography are given particular attention. Agreement between numerical and statistical mechanical results is demonstrated for a large range of parameter values, and over an ensemble of random choices of topography and initial conditions.

Synchronization in Relaxation Oscillator Networks with Conduction Delays

2001 ◽  
Vol 13 (5) ◽  
pp. 1003-1021 ◽  
Author(s):  
Jeffrey J. Fox ◽  
Ciriyam Jayaprakash ◽  
DeLiang Wang ◽  
Shannon R. Campbell
Keyword(s):  
Numerical Simulations ◽  
Coupled Oscillators ◽  
Initial Conditions ◽  
Relaxation Oscillator ◽  
Phase Lag ◽  
Relaxation Oscillators ◽  
Oscillator Networks ◽  
Coupled Networks ◽  
Parameter Values ◽  
Zero Phase

We study locally coupled networks of relaxation oscillators with excitatory connections and conduction delays and propose a mechanism for achieving zero phase-lag synchrony. Our mechanism is based on the observation that different rates of motion along different nullclines of the system can lead to synchrony in the presence of conduction delays. We analyze the system of two coupled oscillators and derive phase compression rates. This analysis indicates how to choose nullclines for individual relaxation oscillators in order to induce rapid synchrony. The numerical simulations demonstrate that our analytical results extend to locally coupled networks with conduction delays and that these networks can attain rapid synchrony with appropriately chosen nullclines and initial conditions. The robustness of the proposed mechanism is verified with respect to different nullclines, variations in parameter values, and initial conditions.

scholarly journals The Impact of Initial Conditions in N-Body Simulations of Debris Discs

2015 ◽  
Vol 32 ◽  
Author(s):  
E. Thilliez ◽  
S. T. Maddison
Keyword(s):  
Numerical Simulations ◽  
Initial Conditions ◽  
Parent Body ◽  
Dust Trapping ◽  
Physical Context ◽  
Disc Width ◽  
Wide Range ◽  
Belt Width ◽  
New Generation ◽  
The Impact

AbstractNumerical simulations are a crucial tool to understand the relationship between debris discs and planetary companions. As debris disc observations are now reaching unprecedented levels of precision over a wide range of wavelengths, an appropriate level of accuracy and consistency is required in numerical simulations to confidently interpret this new generation of observations. However, simulations throughout the literature have been conducted with various initial conditions often with little or no justification. In this paper, we aim to study the dependence on the initial conditions of N-body simulations modelling the interaction between a massive and eccentric planet on an exterior debris disc. To achieve this, we first classify three broad approaches used in the literature and provide some physical context for when each category should be used. We then run a series of N-body simulations, that include radiation forces acting on small grains, with varying initial conditions across the three categories. We test the influence of the initial parent body belt width, eccentricity, and alignment with the planet on the resulting debris disc structure and compare the final peak emission location, disc width and offset of synthetic disc images produced with a radiative transfer code. We also track the evolution of the forced eccentricity of the dust grains induced by the planet, as well as resonance dust trapping. We find that an initially broad parent body belt always results in a broader debris disc than an initially narrow parent body belt. While simulations with a parent body belt with low initial eccentricity (e ~ 0) and high initial eccentricity (0 < e < 0.3) resulted in similar broad discs, we find that purely secular forced initial conditions, where the initial disc eccentricity is set to the forced value and the disc is aligned with the planet, always result in a narrower disc. We conclude that broad debris discs can be modelled by using either a dynamically cold or dynamically warm parent belt, while in contrast eccentric narrow debris rings are reproduced using a secularly forced parent body belt.

Investigations on Aerodynamic Loading Limits of Subsonic Compressor Tandem Cascades: Midspan Flow

2013 ◽  
Author(s):  
Charlotte Hertel ◽  
Christoph Bode ◽  
Dragan Kožulović ◽  
Tim Schneider
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Numerical Simulations ◽  
Pressure Distribution ◽  
Large Range ◽  
Pressure Rise ◽  
Transition Model ◽  
Diffusion Factor ◽  
Aerodynamic Loading ◽  
Tandem Cascades

An optimized subsonic compressor tandem cascade was investigated experimentally and numerically. Since the design aims at incompressible applications, a low inlet Mach number of 0.175 was used. The experiments were carried out at the low speed cascade wind tunnel at the Technische Universität Braunschweig. For the numerical simulations, the CFD-solver TRACE of DLR Cologne was used, together with a curvature corrected k-ω turbulence model and the γ-Reθ transition model. Besides the incidence variation, the aerodynamic loading has also been varied by contracting endwalls. Results are presented and discussed for different inlet angles and endwall contractions: pressure distribution, loss coefficient, turning, pressure rise, AVDR and Mach number. The comparison of experimental and numerical results is always adequate for a large range of incidence. In addition, a comparison is made to an existing high subsonic tandem cascade and conventional cascades. For the latter the Lieblein diffusion factor has been employed as a measure of aerodynamic loading to complete the Lieblein Chart of McGlumphy [1].

scholarly journals Statistical Mechanical Theory of a Closed Oscillating Universe

2009 ◽  
Vol 40 (3) ◽  
pp. 267-275
Author(s):  
A. Pérez-Madrid ◽  
I. Santamaría-Holek
Keyword(s):  
Mechanical Theory ◽  
Statistical Mechanical

Statistical mechanical theory of local compositions

1985 ◽  
Vol 22 (3) ◽  
pp. 253-275 ◽  
Author(s):  
G.Ali Mansoori ◽  
James F. Ely
Keyword(s):  
Mechanical Theory ◽  
Statistical Mechanical
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