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  • 1
    Electronic Resource
    Electronic Resource
    Peristaltically induced motion in a closed cavity with two vibrating walls (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 14 (2002), S. 184-197 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We consider incompressible, viscous fluid confined in a rectangular cavity. Both the bottom and top walls are made of thin membranes. Traveling waves with the same amplitude and frequency but opposite phase are transmitted in these membranes and induce peristaltic motion in the fluid. The induced velocity profiles are determined analytically for small-amplitude waves (ε) and numerically for waves of any amplitude. The analysis consists of a perturbation expansion in terms of the wave amplitude (ε) up to O(ε2). Solutions for large-amplitude oscillations are obtained through the use of a finite element code that employs a moving grid. The numerical code is verified by critically comparing the simulations' predictions with analytical results. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1425841
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  • 2
    Electronic Resource
    Electronic Resource
    Stability of core-annular flow with a small viscosity ratio (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1945-1954 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is known that the stability problem for core-annular flow of very viscous crude oil and water is singular, the water annulus appears to be inviscid with boundary layers at the pipe wall and at the interface. In the present paper, this singular problem is treated by the method of matched asymptotic expansions using ε=m/Rα as a small parameter. There are two cases of instability corresponding to different positions of the critical point in the annulus. One case is when the critical point is far away from the interface, the other is when the critical point is close to the interface within a distance of order ε1/3. In both cases, we derive the equations for the eigenvalues, and give the explicit forms for the neutral curves. The stability problem is also treated by the modified finite element code used by Hu and Joseph [J. Fluid Mech. 205, 359 (1989); Phys. Fluids A 1, 1659 (1989)], taking into account the boundary layers at the pipe wall and at the interface. The results of the two methods agree where they overlap, but the finite element technique goes further.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857670
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  • 3
    Electronic Resource
    Electronic Resource
    Stability of core-annular flow in a rotating pipe (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1677-1685 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linear stability of core-annular flow in rotating pipes is analyzed. Attention is focused on the effects of rotating the pipe and the difference in density of the two fluids. Both axisymmetric and nonaxisymmetric disturbances are considered. Major effects of the viscosity ratio, interfacial tension, radius ratio, and Reynolds number are included. It is found that for two fluids of equal density the rotation of the pipe stabilizes the axisymmetric (n=0) modes of disturbances and destabilizes the nonaxisymmetric modes. Except for small R, where the axisymmetric capillary instability is dominant, the first azimuthal mode of disturbance ||n||=1 is the most unstable. When the heavier fluid is outside centripetal acceleration of the fluid in the rotating pipe is stabilizing; there exists a critical rotating speed above which the flow is stabilized against capillary instability for certain range of small R. When the lighter fluid is outside the flow is always unstable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857532
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  • 4
    Electronic Resource
    Electronic Resource
    Direct simulation of fluid particle motions (1992)
    Springer
    Theoretical and computational fluid dynamics 3 (1992), S. 285-306 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Continuum models of two-phase flows of solids and liquids use constitutive assumptions to close the equations. A more fundamental approach is a “molecular dynamic” simulation of flowing “big” particles based on reliable macroscopic equations for both solid and liquid. We developed a package that simulates the unsteady two-dimensional solid-liquid two-phase flows using the Navier-Stokes equations for the liquid and Newton's equations of motion for the solid particles. The Navier-Stokes equations are solved using a finite-element formulation and Newton's equations of motion are solved using an explicit-implicit scheme. We show that the simplest fully explicit scheme to update the particle motion using Newton's equations is unstable. To correct this instability we propose and implement and Explicit-Implicit Scheme in which, at each time step, the positions of the particles are updated explicitly, the computational domain is remeshed, the solution at the previous time is mapped onto the new mesh, and finally the nonlinear Navier-Stokes equation and the implicitly discretized Newton's equations for particle velocities are solved on the new mesh iteratively. The numerical simulation reveals the effect of vortex shedding on the motion of the cylinders and reproduces the drafting, kissing, and tumbling scenario which is the dominant rearrangement mechanism in two-phase flow of solids and liquids in beds of spheres which are constrained to move in only two dimensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00717645
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  • 5
    Electronic Resource
    Electronic Resource
    Motion of a circular cylinder in a viscous liquid between parallel plates (1995)
    Springer
    Theoretical and computational fluid dynamics 7 (1995), S. 441-455 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The two-dimensional motion of a cylinder in a viscous fluid between two parallel walls of a vertical channel is studied. It is found that when the cylinder moves very closely along one of the channel walls, it always rotates in the direction opposite to that of contact rolling along the nearest wall. When the cylinder is away from the walls, its rotation depends on the Reynolds number of the flow. In this study two numerical methods were used. One is for the unsteady motion of a sedimenting cylinder initially released from a position close to one of the channel walls, where the Navier-Stokes equations are solved for the fluid and Newton's equations of motion are solved for the rigid cylinder. The other method is for the steady flow in which a cylinder is fixed in a uniform flow field where the channel walls are sliding past the cylinder at the speed of the approaching flow, or equivalently a cylinder is moving with a constant velocity in a quiescent fluid. The flow field, the drag, the side force (lift), and the torque experienced by the cylinder are studied in detail. The effects of the cylinder location in the channel, the size of the channel relative to the cylinder diameter, and the Reynolds number of the flow are examined. In the limit when the cylinder is translating very closely along one of the walls, the flow in the gap between the cylinder and the wall is solved analytically using lubrication theory, and the numerical solution in the other region is used to piece together the whole flow field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418142
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  • 6
    Electronic Resource
    Electronic Resource
    Miscible displacement in a Hele-Shaw cell (1992)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 43 (1992), S. 626-644 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We formulated a theory of simple mixtures of incompressible miscible liquids in terms of the mass averaged velocityu and the solenoidal volume averaged velocityW, We derived simplified equations for miscible displacement in a Hele-Shaw cell. We obtained a steady solution of these equations corresponding to displacement under gravity with prescribed values of concentration and mean normal stress at the inlet and exit of the cell. We studied the stability of this steady flow. This differs from previous works which treat the stability of unsteady miscible displacement using a quasi-static assumption and classical equations based on divu=0. In our problem, replacingu withW gives rise to a difference in the mean normal stress, which alters the pressure drop across the cell and changes the velocity of free fall. We found that the stability equations are the same in the two formulations, but the boundary conditions are slightly different; however the difference will be small if diffusion is slow or the thickness of the cell is small. The results show that steady miscible displacement in a Hele-Shaw cell is stable to long and short waves. Within certain ranges of parameters, the displacement of glycerin into water can be unstable. This instability is basically of a Rayleigh-Taylor type, regularized by diffusion. As the diffusion parameterS becomes smaller, the waves of disturbances become finer and are confined to an increasingly thin diffusion layer. Water displacing glycerin is always stable. This is due to the fact that the steady equilibrium profile is not steep enough to create a fingering instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00946254
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  • 7
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    Shape Dynamics and Rheology of Soft Elastic Particles in a Shear Flow (2012)
    American Physical Society
    Details
    Publication Date: 2012-01-31
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 8
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    Publisher Correction: An immunoregulatory and tissue-residency program modulated by c-MAF in human TH17 cells (2018)
    Springer Nature
    Details
    Publication Date: 2018
    Print ISSN: 1529-2908
    Electronic ISSN: 1529-2916
    Topics: Biology , Medicine
    Published by Springer Nature
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  • 9
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    Electrophoresis of Concentrically and Eccentrically Positioned Cylindrical Particles in a Long Tube (2004)
    American Chemical Society
    Details
    Publication Date: 2004-03-01
    Print ISSN: 0743-7463
    Electronic ISSN: 1520-5827
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 10
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    IJERPH, Vol. 15, Pages 1999: A Bayesian Downscaler Model to Estimate Daily PM2.5 Levels in the Conterminous US (2018)
    MDPI Publishing
    Details
    Publication Date: 2018-09-14
    Description: IJERPH, Vol. 15, Pages 1999: A Bayesian Downscaler Model to Estimate Daily PM2.5 Levels in the Conterminous US International Journal of Environmental Research and Public Health doi: 10.3390/ijerph15091999 Authors: Yikai Wang Xuefei Hu Howard H. Chang Lance A. Waller Jessica H. Belle Yang Liu There has been growing interest in extending the coverage of ground particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) monitoring networks based on satellite remote sensing data. With broad spatial and temporal coverage, a satellite-based monitoring network has a strong potential to complement the ground monitor system in terms of the spatiotemporal availability of the air quality data. However, most existing calibration models focus on a relatively small spatial domain and cannot be generalized to a national study. In this paper, we proposed a statistically reliable and interpretable national modeling framework based on Bayesian downscaling methods to be applied to the calibration of the daily ground PM2.5 concentrations across the conterminous United States using satellite-retrieved aerosol optical depth (AOD) and other ancillary predictors in 2011. Our approach flexibly models the PM2.5 versus AOD and the potential related geographical factors varying across the climate regions and yields spatial- and temporal-specific parameters to enhance model interpretability. Moreover, our model accurately predicted the national PM2.5 with an R2 at 70% and generated reliable annual and seasonal PM2.5 concentration maps with its SD. Overall, this modeling framework can be applied to national-scale PM2.5 exposure assessments and can also quantify the prediction errors.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by MDPI Publishing
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