Reactive convective dissolution with differential diffusivities: Nonlinear simulations of onset times and asymptotic fluxes

2020 ◽  
Vol 5 (10) ◽  
Author(s):  
M. Jotkar ◽  
L. Rongy ◽  
A. De Wit
Keyword(s):  
Nonlinear Simulations

Density-driven unstable flows of miscible fluids in a Hele-Shaw cell

2002 ◽  
Vol 451 ◽  
pp. 239-260 ◽  
Author(s):  
J. FERNANDEZ ◽  
P. KUROWSKI ◽  
P. PETITJEANS ◽  
E. MEIBURG
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Brinkman Equation ◽  
Length Scale ◽  
Dominant Wavelength ◽  
Miscible Fluids ◽  
Nonlinear Simulations ◽  
Instability Growth ◽  
Gap Width ◽  
Hele Shaw Cell

Density-driven instabilities between miscible fluids in a vertical Hele-Shaw cell are investigated by means of experimental measurements, as well as two- and three-dimensional numerical simulations. The experiments focus on the early stages of the instability growth, and they provide detailed information regarding the growth rates and most amplified wavenumbers as a function of the governing Rayleigh number Ra. They identify two clearly distinct parameter regimes: a low-Ra, ‘Hele-Shaw’ regime in which the dominant wavelength scales as Ra−1, and a high-Ra ‘gap’ regime in which the length scale of the instability is 5±1 times the gap width. The experiments are compared to a recent linear stability analysis based on the Brinkman equation. The analytical dispersion relationship for a step-like density profile reproduces the experimentally observed trend across the entire Ra range. Nonlinear simulations based on the two- and three-dimensional Stokes equations indicate that the high-Ra regime is characterized by an instability across the gap, wheras in the low-Ra regime a spanwise Hele-Shaw mode dominates.

Nonlinear Simulations of the Bump-on-Tail Instabilities in Tokamak Plasmas

2021 ◽  
Vol 38 (4) ◽  
pp. 045202
Author(s):  
Yumei Hou ◽  
Wei Chen ◽  
Liming Yu ◽  
Yunpeng Zou ◽  
Min Xu ◽  
...  
Keyword(s):  
Tokamak Plasmas ◽  
Nonlinear Simulations

scholarly journals Steep unidirectional wave groups – fully nonlinear simulations vs. experiments

2015 ◽  
Vol 2 (4) ◽  
pp. 1159-1195 ◽  
Author(s):  
L. Shemer ◽  
B. K. Ee
Keyword(s):  
Wave Breaking ◽  
Surface Elevation ◽  
Computational Results ◽  
Local Surface ◽  
Qualitative Comparison ◽  
Wave Groups ◽  
Fully Nonlinear ◽  
Nonlinear Simulations ◽  
Velocity Of Propagation ◽  
Steep Waves

Abstract. A method was developed to carry out detailed qualitative comparison of fully nonlinear computations with the measurements of unidirectional wave groups. Computational results on evolving wave groups were compared with the available experiments. The local surface elevation variation, evolution of envelope shapes, the velocity of propagation of the steepest crests in the group and their relation to the height of the crests were obtained numerically and experimentally. Conditions corresponding to incipient wave breaking were investigated in greater detail. The results shed additional light on the limits of applicability of the computational results, as well as on mechanisms leading to the breaking of steep waves.

scholarly journals A Broadband Ultrathin Nonlinear Switching Metamaterial

2017 ◽  
Vol 6 (2) ◽  
pp. 64
Author(s):  
E. Zarnousheh Farahani ◽  
S. Jarchi ◽  
A. Keshtkar
Keyword(s):  
Incident Wave ◽  
Optimization Method ◽  
Resonant Mode ◽  
Unit Cell ◽  
Incident Power ◽  
Full Wave ◽  
Effective Impedance ◽  
Nonlinear Simulations ◽  
Switching Property ◽  
Transmission And Reflection

In this paper, an ultrathin planar nonlinear metamaterial slab is designed and simulated. Nonlinearity is provided through placing diodes in each metamaterial unit cell. The diodes are auto-biased and activated by an incident wave. The proposed structure represents a broadband switching property between two transmission and reflection states depending on the intensity of the incident wave. High permittivity values are presented creating a near zero effective impedance at low power states, around the second resonant mode of the structure unit cell; as the result, the incident wave is reflected. Increasing the incident power to the level which can activate the loaded diodes in the structure results in elimination of the resonance and consequently a drop in the permittivity values near the permeability one as well as a switch to the transmission state. A full wave as well as a nonlinear simulations are performed. An optimization method based on weed colonization is applied to the unit cell of the metamaterial slab to achieve the maximum switching bandwidth. The structure represents a 24% switching bandwidth of a 10 dB reduction in the reflection coefficient.

Spatial Extreme Value Analysis of Nonlinear Simulations of Random Surface Waves

2004 ◽  
Author(s):  
Harald E. Krogstad ◽  
Jingdong Liu ◽  
Herve´ Socquet-Juglard ◽  
Kristian B. Dysthe ◽  
Karsten Trulsen
Keyword(s):  
Gravity Waves ◽  
Ocean Waves ◽  
Spatial Characteristic ◽  
Extreme Value Analysis ◽  
Extreme Waves ◽  
Random Surface ◽  
Value Analysis ◽  
Nonlinear Simulations ◽  
Gaussian Theory ◽  
Reconstructed Wave

The paper first recalls the Slepian Model Representation and a theorem of V. I. Piterbarg as generic tools for analyzing the spatial characteristic of ocean waves. We then consider numerical simulations of random surface gravity waves carried out in space and time by means of the modified nonlinear Schro¨dinger equation. It is shown that the extreme waves in the simulations are steeper and more asymmetric than predicted by the Gaussian theory. Moreover, the reconstructed wave fields shows extreme crest heights well in excess of what is expected from the Gaussian theory.

Two-dimensional Nonlinear Simulations of Temperature-anisotropy Instabilities with a Proton-alpha Drift

2018 ◽  
Vol 856 (2) ◽  
pp. 153 ◽  
Author(s):  
S. A. Markovskii ◽  
Benjamin D. G. Chandran ◽  
Bernard J. Vasquez
Keyword(s):  
Two Dimensional ◽  
Temperature Anisotropy ◽  
Nonlinear Simulations

Modelling of Site Amplification via Large Scale Nonlinear Simulations with Applications to North America

2018 ◽  
Author(s):  
Youssef M. A. Hashash ◽  
Joseph Harmon ◽  
Okan Ilhan ◽  
Jonathan P. Stewart ◽  
Ellen M. Rathje ◽  
...  
Keyword(s):  
North America ◽  
Large Scale ◽  
Site Amplification ◽  
Nonlinear Simulations

scholarly journals Rossby Wave Instability of Thin Accretion Disks. III. Nonlinear Simulations

2001 ◽  
Vol 551 (2) ◽  
pp. 874-896 ◽  
Author(s):  
H. Li ◽  
S. A. Colgate ◽  
B. Wendroff ◽  
R. Liska
Keyword(s):  
Accretion Disks ◽  
Rossby Wave ◽  
Wave Instability ◽  
Nonlinear Simulations
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