scholarly journals Semiquantum Chaos in Two GaAs Quantum Dots Coupled Linearly and Quadratically by Two Harmonic Potentials in Two Dimensions

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Emile Godwe ◽  
Justin Mibaile ◽  
Betchewe Gambo ◽  
Serge Y. Doka
Keyword(s):  
Quantum Dots ◽  
Numerical Simulations ◽  
Chaotic Behavior ◽  
Two Dimensions ◽  
Periodic Behavior ◽  
Coupling Parameters ◽  
Ehrenfest Theorem

We analyze the phenomenon of semiquantum chaos in two GaAs quantum dots coupled linearly and quadratically by two harmonic potentials. We show how semiquantum dynamics should be derived via the Ehrenfest theorem. The extended Ehrenfest theorem in two dimensions is used to study the system. The numerical simulations reveal that, by varying the interdot distance and coupling parameters, the system can exhibit either periodic or quasi-periodic behavior and chaotic behavior.

Direct numerical simulations of Rayleigh–Bénard convection in water with non-Oberbeck–Boussinesq effects

2019 ◽  
Vol 881 ◽  
pp. 1073-1096 ◽  
Author(s):  
Andreas D. Demou ◽  
Dimokratis G. E. Grigoriadis
Keyword(s):  
Numerical Simulations ◽  
Two Dimensions ◽  
Direct Numerical Simulations ◽  
Wall Region ◽  
Number Range ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Near Wall

Rayleigh–Bénard convection in water is studied by means of direct numerical simulations, taking into account the variation of properties. The simulations considered a three-dimensional (3-D) cavity with a square cross-section and its two-dimensional (2-D) equivalent, covering a Rayleigh number range of $10^{6}\leqslant Ra\leqslant 10^{9}$ and using temperature differences up to 60 K. The main objectives of this study are (i) to investigate and report differences obtained by 2-D and 3-D simulations and (ii) to provide a first appreciation of the non-Oberbeck–Boussinesq (NOB) effects on the near-wall time-averaged and root-mean-squared (r.m.s.) temperature fields. The Nusselt number and the thermal boundary layer thickness exhibit the most pronounced differences when calculated in two dimensions and three dimensions, even though the $Ra$ scaling exponents are similar. These differences are closely related to the modification of the large-scale circulation pattern and become less pronounced when the NOB values are normalised with the respective Oberbeck–Boussinesq (OB) values. It is also demonstrated that NOB effects modify the near-wall temperature statistics, promoting the breaking of the top–bottom symmetry which characterises the OB approximation. The most prominent NOB effect in the near-wall region is the modification of the maximum r.m.s. values of temperature, which are found to increase at the top and decrease at the bottom of the cavity.

Delay stabilization of periodic orbits in coupled oscillator systems

2010 ◽  
Vol 368 (1911) ◽  
pp. 319-341 ◽  
Author(s):  
B. Fiedler ◽  
V. Flunkert ◽  
P. Hövel ◽  
E. Schöll
Keyword(s):  
Normal Form ◽  
Numerical Simulations ◽  
Periodic Orbits ◽  
Coupled Oscillators ◽  
Coupled Oscillator ◽  
Non Invasive ◽  
Coupling Parameters ◽  
Necessary And Sufficient ◽  
Time Delayed Feedback ◽  
Coupled Oscillator Systems

We study diffusively coupled oscillators in Hopf normal form. By introducing a non-invasive delay coupling, we are able to stabilize the inherently unstable anti-phase orbits. For the super- and subcritical cases, we state a condition on the oscillator’s nonlinearity that is necessary and sufficient to find coupling parameters for successful stabilization. We prove these conditions and review previous results on the stabilization of odd-number orbits by time-delayed feedback. Finally, we illustrate the results with numerical simulations.

SPH Numerical Simulations of the Deformation of a Liquid Surface in Two Dimensions

2019 ◽  
pp. 63-75
Author(s):  
Cristian Cáliz-Reyes ◽  
Laura A. Ibarra-Bracamontes ◽  
Rosanna Bonasia ◽  
Gonzalo Viramontes-Gamboa
Keyword(s):  
Numerical Simulations ◽  
Liquid Surface ◽  
Two Dimensions

scholarly journals Seismic stimulation for enhanced oil recovery

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. O23-O35 ◽  
Author(s):  
Steven R. Pride ◽  
Eirik G. Flekkøy ◽  
Olav Aursjø
Keyword(s):  
Pressure Gradient ◽  
Numerical Simulations ◽  
Oil Recovery ◽  
Scale Effects ◽  
Fluid Pressure ◽  
Oil Production ◽  
Two Dimensions ◽  
Lattice Boltzmann Model ◽  
Pore Scale ◽  
Capillary Barriers

The pore-scale effects of seismic stimulation on two-phase flow are modeled numerically in random 2D grain-pack geometries. Seismic stimulation aims to enhance oil production by sending seismic waves across a reservoir to liberate immobile patches of oil. For seismic amplitudes above a well-defined (analytically expressed) dimensionless criterion, the force perturbation associated with the waves indeed can liberate oil trapped on capillary barriers and get it flowing again under the background pressure gradient. Subsequent coalescence of the freed oil droplets acts to enhance oil movement further because longer bubbles overcome capillary barriers more efficiently than shorter bubbles do. Poroelasticity theory defines the effective force that a seismic wave adds to the background fluid-pressure gradient. The lattice-Boltzmann model in two dimensions is used to perform pore-scale numerical simulations. Dimensionless numbers (groups of material and force parameters) involved in seismic stimulation were defined carefully so that numerical simulations could be applied to field-scale conditions. Using defined analytical criteria, there is a significant range of reservoir conditions over which seismic stimulation can be expected to enhance oil production.

SCALING BEHAVIOUR OF A MULTIPLY CONNECTED FLUCTUATING INTERFACE IN TWO DIMENSIONS

Fractals ◽  
2003 ◽  
Vol 11 (supp01) ◽  
pp. 227-232
Author(s):  
AYŞE ERZAN ◽  
HÜSEY.IN KAYA ◽  
ALKAN KABAKÇIOĞLU
Keyword(s):  
Kinetic Model ◽  
Numerical Simulations ◽  
Average Velocity ◽  
Two Dimensions ◽  
Scaling Exponents ◽  
Multiply Connected ◽  
Fractal Set ◽  
Scaling Behaviour ◽  
Infinite String

We consider a one-parameter kinetic model for a fluctuating interface which can be thought of as an infinite string decorated with infinitely many closed strings. Numerical simulations show that a number of scaling exponents describing this string system may be related to the Kardar-Parisi-Zhang exponents. However, as the average velocity of the infinite string is taken to zero, and the string system becomes an isotropic fractal set, we also find new exponents which cannot be reduced to previously known ones.

scholarly journals Simulation of Quantum-Dot Structures in Si/SiO2

VLSI Design ◽  
1998 ◽  
Vol 6 (1-4) ◽  
pp. 335-339 ◽  
Author(s):  
Minhan Chen ◽  
Wolfgang Porod
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Material System ◽  
Exposed Surface ◽  
Confining Potential ◽  
The Poisson Equation ◽  
Charge Model ◽  
Electron Quantum

We present numerical simulations for the design of gated few-electron quantum dot structures in the Si/SiO2 material system. Because of the vicinity of the quantum dots to the exposed surface, we take special care in treating the boundary conditions at the oxide/vacuum interfaces. In our simulations, the confining potential is obtained from the Poisson equation with a Thomas-Fermi charge model. We find that the dot occupancy can be effectively controlled in the few-electron regime.

Enhancement of Mixing in a Microchannel by Using AC-Electroosmotic Effect

2008 ◽  
Author(s):  
Yangyang Wang ◽  
Sangmo Kang ◽  
Yongkweon Suh
Keyword(s):  
Numerical Simulations ◽  
Chaotic Behavior ◽  
Electrode Array ◽  
Longitudinal Direction ◽  
Central Line ◽  
Transverse Flow ◽  
Electrode Pair ◽  
Mixing Performance ◽  
Commercial Code ◽  
Micro Mixer

This study has focused on optimizing the AC-electroosmotic micro-mixer, which is composed of a microchannel with an array of rectangular electrodes attached on the bottom wall. The electrode array is spatial-periodically arranged in pairs symmetric with respect to the longitudinal central line. An AC electrode field is applied to the electrodes, which drives the secondary transverse flow in a circulating cell mode near the electrodes. The main flow along the channel longitudinal direction plus this secondary transverse flow contribute to the stretching and folding of the fluid flow, that is the chaotic behavior, and thus to the enhancement of the fluid mixing. To design the better micro-mixer, numerical simulations have been performed by using a commercial code (CFX 10). In the simulations, the concept of mixing index is employed to evaluate the mixing performance as well as to optimize the size and spacing of each electrode in one pair. It is found that the optimum design of one electrode pair, which leads to the best mixing performance, is not simply harmonic one. When the length ratio of the two electrodes in a pair closes to 2:1, the best mixing effect can be attained. The flow pattern was visualized. Furthermore, the velocity field will be measured with a PTV technique to validate the numerical simulations.

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