A gas pressure gradient‐dependent subgrid drift velocity model for drag prediction in fluidized gas–particle flows

AIChE Journal ◽  
2019 ◽  
Vol 66 (4) ◽  
Author(s):  
Ming Jiang ◽  
Xiao Chen ◽  
Qiang Zhou
Keyword(s):  
Pressure Gradient ◽  
Drift Velocity ◽  
Velocity Model ◽  
Gas Pressure ◽  
Particle Flows ◽  
Drag Prediction

A functional subgrid drift velocity model for filtered drag prediction in dense fluidized bed

AIChE Journal ◽  
2011 ◽  
Vol 58 (4) ◽  
pp. 1084-1098 ◽  
Author(s):  
Jean-François Parmentier ◽  
Olivier Simonin ◽  
Olivier Delsart
Keyword(s):  
Fluidized Bed ◽  
Drift Velocity ◽  
Velocity Model ◽  
Drag Prediction

scholarly journals The effects of magnetic field strength on the properties of wind generated from hot accretion flow

2018 ◽  
Vol 615 ◽  
pp. A35 ◽  
Author(s):  
De-Fu Bu ◽  
Amin Mosallanezhad
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Pressure Gradient ◽  
Magnetic Field Strength ◽  
Magnetic Pressure ◽  
Gas Pressure ◽  
Accretion Flow ◽  
Accretion Flows ◽  
Black Hole Accretion ◽  
The Magnetic Field

Context. Observations indicate that wind can be generated in hot accretion flow. Wind generated from weakly magnetized accretion flow has been studied. However, the properties of wind generated from strongly magnetized hot accretion flow have not been studied. Aims. In this paper, we study the properties of wind generated from both weakly and strongly magnetized accretion flow. We focus on how the magnetic field strength affects the wind properties. Methods. We solve steady-state two-dimensional magnetohydrodynamic equations of black hole accretion in the presence of a largescale magnetic field. We assume self-similarity in radial direction. The magnetic field is assumed to be evenly symmetric with the equatorial plane. Results. We find that wind exists in both weakly and strongly magnetized accretion flows. When the magnetic field is weak (magnetic pressure is more than two orders of magnitude smaller than gas pressure), wind is driven by gas pressure gradient and centrifugal forces. When the magnetic field is strong (magnetic pressure is slightly smaller than gas pressure), wind is driven by gas pressure gradient and magnetic pressure gradient forces. The power of wind in the strongly magnetized case is just slightly larger than that in the weakly magnetized case. The power of wind lies in a range PW ~ 10−4–10−3 Ṁinc2, with Ṁin and c being mass inflow rate and speed of light, respectively. The possible role of wind in active galactic nuclei feedback is briefly discussed.

scholarly journals Numerical Analysis of the Mud Inflow Model of Fractured Rock Mass Based on Particle Flow

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Yongjian Pan ◽  
Huajun Wang ◽  
Yanlin Zhao ◽  
Qiang Liu ◽  
Shilin Luo
Keyword(s):  
Rock Mass ◽  
Pressure Gradient ◽  
Flow Direction ◽  
Fractured Rock ◽  
Water Pressure ◽  
Water Inrush ◽  
Quadratic Function ◽  
Particle Flow ◽  
Fractured Rock Mass ◽  
Particle Flows

Water inrush and mud outburst are one of the crucial engineering disasters commonly encountered during the construction of many railways and tunnels in karst areas. In this paper, based on fluid dynamics theory and discrete element method, we established a fractured rock mass mud inflow model using particle flow PFC3D numerical software, simulated the whole process of fractured rock mass mud inflow, and discussed the effect of particle size and flow velocity on the change of pressure gradient. The numerical simulation results show that the movement of particles at the corner of the wall when the water pressure is first applied occurs similar to the vortex phenomenon, with the running time increases, the flow direction of particles changes, the vortex phenomenon disappears, and the flow direction of particles at the corner points to the fracture; in the initial stage, the slope of the particle flows rate curves increases in time, and the quadratic function is used for fitting. After the percolation velocity of particles reaches stability, the slope of the curve remains constant, and the primary function is used for fitting; the particle flow rate and pressure gradient are influenced by a variety of factors, and they approximately satisfy the exponential function of an “S” curve.

scholarly journals The Mass and Size Distribution of Planetesimals Formed by the Streaming Instability. II. The Effect of the Radial Gas Pressure Gradient

2019 ◽  
Vol 883 (2) ◽  
pp. 192 ◽  
Author(s):  
Charles P. Abod ◽  
Jacob B. Simon ◽  
Rixin Li ◽  
Philip J. Armitage ◽  
Andrew N. Youdin ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Size Distribution ◽  
Gas Pressure ◽  
Streaming Instability

On the role and the origin of the gas pressure gradient in the discharge of fine solids from hoppers

2003 ◽  
Vol 58 (23-24) ◽  
pp. 5269-5278 ◽  
Author(s):  
Diego Barletta ◽  
Giorgio Donsı̀ ◽  
Giovanna Ferrari ◽  
Massimo Poletto
Keyword(s):  
Pressure Gradient ◽  
Gas Pressure

Drift-Velocity Closure Relationships for Slug Two-Phase High-Viscosity Oil Flow in Pipes

SPE Journal ◽  
2012 ◽  
Vol 17 (02) ◽  
pp. 593-601 ◽  
Author(s):  
B.C.. C. Jeyachandra ◽  
B.. Gokcal ◽  
A.. Al-Sarkhi ◽  
C.. Sarica ◽  
A.K.. K. Sharma
Keyword(s):  
Drift Velocity ◽  
Velocity Model ◽  
High Viscosity ◽  
Inviscid Fluid ◽  
Flow Loop ◽  
Oil Viscosity ◽  
Two Phase ◽  
Flow Models ◽  
Inclination Angles ◽  
Inclined Pipes

Summary The drift velocity of a gas bubble penetrating into a stagnant liquid is investigated experimentally in this paper. It is part of the translational slug velocity. The existing equations for the drift velocity are either developed by using the results of Benjamin (1968) analysis assuming inviscid fluid flow or correlated using air/water data. Effects of surface tension and viscosity usually are neglected. However, the drift velocity is expected to be affected by high oil viscosity. In this study, the work of Gokcal et al. (2009) has been extended for different pipe diameters and viscosity range. The effects of high oil viscosity and pipe diameter on drift velocity for horizontal and upward-inclined pipes are investigated. The experiments are performed on a flow loop with a test section with 50.8-, 76.2-, and 152.4-mm inside diameter (ID) for inclination angles of 0 to 90°. Water and viscous oil are used as test fluids. New correlation for drift velocity in horizontal pipes of different diameters and liquid viscosities is developed on the basis of experimental data. A new drift-velocity model/approach are proposed for high oil viscosity, valid for inclined pipes inclined from horizontal to vertical. The proposed comprehensive closure relationships are expected to improve the performance of two-phase-flow models for high-viscosity oils in the slug flow regime.

The motion of slow positive ions in gases - Mobilities of potassium and nitrogen ions in nitrogen

1966 ◽  
Vol 259 (1100) ◽  
pp. 321-330 ◽  
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficient ◽  
Pressure Gradient ◽  
Drift Velocity ◽  
Lateral Diffusion ◽  
Electrode System ◽  
Published Data ◽  
Positive Ions ◽  
Nitrogen Ions ◽  
Differential Pumping

It was shown in part I that there is a need for further experimental data on the drift velocity W of ions in gases such as nitrogen and argon where there are still unresolved problems. In addition, measurements of quantities such as the diffusion coefficient D and mean energy e are required for ions in most gases since published data on these quantities are scanty. In principle, it is possible to determine these quantities by measuring both the drift velocity W and the ratio W/D for selected groups of ions in an apparatus combining a time of drift electrode system, similar to that used by Tyndall et al. (1928) and Tyndall (1938), with a lateral diffusion system similar to that used by Townsend (1925) for the measurement of the ratio W/D for electrons. The advantages of using a time of drift selector for the ions rather than, say, a mass spectrometer are first, that there is no pressure gradient between the selector and the diffusion apparatus, so that no differential pumping is necessary, and secondly, that not only are the ions selected but their mobility is measured at the same time.

scholarly journals Dynamic Characterization during Gas Initial Desorption of Coal Particles and Its Influence on the Initiation of Coal and Gas Outbursts

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1101
Author(s):  
Chaojie Wang ◽  
Xiaowei Li ◽  
Changhang Xu ◽  
Yujia Chen ◽  
Zexiang Tang ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Dynamic Effect ◽  
Coal Mass ◽  
Gas Pressure ◽  
Coal Surface ◽  
Dynamic Characterization ◽  
Coal Particles ◽  
Expansion Energy ◽  
Gas Expansion ◽  
Two Peaks

The law of gas initial desorption from coals is greatly important for understanding the occurrence mechanism and predicting coal and gas outburst (hereinafter referred to as ‘outburst’). However, dynamic characterization of gas initial desorption remains to be investigated. In this study, by monitoring the gas pressure and temperature of tectonically deformed (TD) coal and primary-undeformed (PU) coal, we established the evolution laws of gas key parameters during the initial desorption. The results indicate that the gas pressure drop rate, mass flow rate, initial desorption rate, and gas velocity increase with increasing gas pressure, with stronger gas dynamic effect, generating a high pressure gradient on the coal surface. Under the same gas pressure, the pressure gradient formed on the TD coal surface is greater than that formed on the surface of the PU coal, resulting in easily initiating an outburst in the TD coal. Moreover, the increased gas pressure increases temperature change rates (falling rate and rising rate) of coal mass. The minimum and final stable temperatures in the TD coal are generally lower compared to the PU coal. The releasing process of gas expansion energy can be divided into two stages exhibiting two peaks which increase as gas pressure increases. The two peak values for the TD coal both are about 2–3 times of those of the PU coal. In addition, the total gas expansion energy released by TD coal is far greater than that released by PU coal. The two peaks and the total values of gas expansion energy also prove that the damage of gas pressure to coal mass increases with the increased pressure, more likely producing pulverized coals and more prone to initiate an outburst.

scholarly journals An Alternative Model of Rotation Curve that Explains Anomalous Orbital Velocity, Mass Discrepancy and Structure of Some Galaxies

2020 ◽  
Author(s):  
Paul C. Rivera
Keyword(s):  
Black Hole ◽  
Pressure Gradient ◽  
Surface Brightness ◽  
Rotation Velocity ◽  
Velocity Model ◽  
Gradient Force ◽  
Galactic Rotation ◽  
Pressure Gradient Force ◽  
Massive Black Hole ◽  
Fisher Relation

A new model of galaxy rotation based on the cyclostrophic model of vortices found in nature is developed. The model is tested using the SPARC dataset of 175 galaxies and a smaller dataset comprising of 60 galaxies. Analysis of the datasets showed that galactic rotation can be adequately described using the observed surface brightness of galaxies and the newly developed cyclostrophic velocity model. The use of the luminosity and the inverse mass-to-light ratio in lieu of the surface brightness, also yield a very good fit of the observed and computed galaxy rotation velocity. Evidently, galactic rotation greatly depends on the cyclostrophic balance of the pressure gradient and the centrifugal forces and the seismic-induced radial expansion occurring in various stars. This is the most probable origin of the action of a single force law that has been overlooked in previous studies. Therefore, the need for a super-massive black hole at the center of galaxies or hidden dark matter can be eliminated. Attractive gravitational force can occur even without a massive black hole at the center of galaxies. There appears to be a pressure gradient force between the center and the outer parts of galaxies that sustains attraction. The cyclostrophic model appears to be the physical basis of the Tully-Fisher relation. Furthermore, the missing mass problem associated with galactic rotation can be attributed to the orbital expansion of celestial objects perturbed by seismic-induced forces. In addition, massive tremors or starquakes may create a domino effect in perturbing nearby stars along the axis of the seismic-induced force and this could result in the formation of elliptical galaxies as the orbits of seismic-perturbed neighboring stars become larger.

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