To the Interchange Instability Criterion in the Magnetosphere in the Presence of Velocity Shear

2020 ◽  
Vol 125 (10) ◽  
Author(s):  
George V. Khazanov ◽  
Emanuel N. Krivorutsky ◽  
Margaret W. Chen ◽  
Colby L. Lemon
Keyword(s):  
Velocity Shear ◽  
Instability Criterion ◽  
Interchange Instability

Vortex chains in development of interchange instability in plasma with velocity shear

1996 ◽  
Vol 53 (3) ◽  
pp. 336-338 ◽  
Author(s):  
N Aleksić ◽  
D Jovanović ◽  
J Vranješ
Keyword(s):  
Velocity Shear ◽  
Interchange Instability

On linear wave motions in magnetic-velocity shears

1977 ◽  
Vol 285 (1328) ◽  
pp. 607-636 ◽  
Keyword(s):  
Differential Equation ◽  
Critical Level ◽  
Velocity Shear ◽  
Linear Wave ◽  
Wave Amplification ◽  
Isothermal Fluid ◽  
Governing Differential Equation ◽  
Boussinesq Fluid ◽  
Propagation Properties ◽  
Background State

The propagation properties of linear wave motions in magnetic and/or velocity shears which vary in one coordinate z (say) are usually governed by a second order linear ordinary differential equation in the independent variable z. It is proved that associated with any such differential equation there always exists a quantity A which is independent of z. By employing A a measure of the intensity of the wave, this result is used to investigate the general propagation properties of hydromagnetic-gravity waves (e.g. critical level absorption, valve effects and wave amplification) in magnetic and/or velocity shears, using a full wave treatment. When variations in the basic state are included, the governing differential equation usually has more singularities than it has in the W.K.B.J. approximation, which neglects all variations in the background state. The study of a wide variety of models shows that critical level behaviour occurs only at the singularities predicted by the W.K.B.J. approximation. Although the solutions of the differential equation are necessarily singular at the irregularities whose presence is solely due to the inclusion of variations in the basic state, the intensity of the wave (as measured by A) is continuous there. Also the valve effect is found to persist whatever the relation between the wavelength of the wave and the scale of variations of the background state. In addition, it is shown that a hydromagnetic-gravity wave incident upon a finite magnetic and/or velocity shear can be amplified (or over-reflected) in the absence of any critical levels within the shear layer. In a Boussinesq fluid rotating uniformly about the vertical, wave amplification can occur if the horizontal vertically sheared flow and magnetic field are perpendicular. In a compressible isothermal fluid, on the other hand, wave amplification not only occurs in both magnetic-velocity and velocity shears but also in a magnetic shear acting alone.

scholarly journals Rheological Properties of Wood–Plastic Composites by 3D Numerical Simulations: Different Components

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 417
Author(s):  
Xingcong Lv ◽  
Xiaolong Hao ◽  
Rongxian Ou ◽  
Tao Liu ◽  
Chuigen Guo ◽  
...  
Keyword(s):  
Flow Field ◽  
Rheological Properties ◽  
Wood Fiber ◽  
Velocity Shear ◽  
Wood Plastic Composites ◽  
Shear Rates ◽  
Plastic Composites ◽  
Power Law Fluids ◽  
Field Information ◽  
Computational Fluid Dynamics Cfd

The rheological properties of wood–plastic composites (WPCs) with different wood fiber contents were investigated using a rotational rheometer under low shear rates. The flow field information was analyzed and simulated by Ansys Polyflow software. The results showed that the WPCs with different wood fiber contents behaved as typical power-law fluids. A higher wood fiber content increased the shear thinning ability and pseudoplasticity of the WPCs. The pressure, velocity, shear rate, and viscosity distributions of the WPC during extrusion could be predicted by computational fluid dynamics (CFD) Ansys Polyflow software to explore the effects of different components on the flow field of WPCs.

Predicting Sulfidic and Naphthenic Acid Corrosion

CORROSION ◽  
2009 ◽  
Vol 65 (12) ◽  
pp. 831-844 ◽  
Author(s):  
J. Hau
Keyword(s):  
Shear Stress ◽  
Exposure Time ◽  
Acid Corrosion ◽  
Naphthenic Acid ◽  
Naphthenic Acids ◽  
Sulfur Compounds ◽  
Velocity Shear ◽  
Threshold Behavior ◽  
Temperature Range ◽  
Si Content

Abstract This paper reviews the factors that are hindering the development of models to predict corrosion due to sulfur compounds, naphthenic acids, or both, acting simultaneously on steels within the temperature range typically from 230°C to 400°C. These factors are identified as data scattering that do not distribute normally, variables or factors that do not exert their influence in a gradual manner but as a threshold behavior, and the interactions between the factors of sulfidic and naphthenic acid corrosion; exposure time, temperature, and velocity (shear stress); and the chromium and molybdenum content of the steels (Si content is not discussed). Not dealing with the interactions is probably the largest obstacle, followed by data scattering.

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