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Subject: search.filters.subject.Hydrodynamic permeability

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    Electroosmotic flow in a concentrated suspension of polyelectrolyte-grafted solid cylindrical particles: a particle-in-cell approach
    (AIP, 2024-12) Tiwari, Ashish
    The present study attempts to deal with electrokinetic and hydrodynamic characteristics of mixed electroosmotic and pressure-driven flow through a membrane composed of a swarm of poly-electrolyte-coated solid cylindrical particles. The unit cell model approach is utilized to analyze the hydrodynamic interactions between particles of the multiparticle system. The electroosmotic flow is generated under the influence of an externally applied electric field, and a pressure gradient is assumed in the axial direction of the cylinder. The poly-electrolyte coating over the solid cylindrical particle is considered as a heterogeneous porous medium having variable permeability characteristics. The electrolyte fluid contains charged ions, which can be present and migrate in both inside and outside of the poly-electrolyte layer (PEL). Hence, PEL acts as a semi-permeable porous layer. The PEL is referred to as a fixed charged layer (FCL) owing to an extra number density of immobilized charged ions, fixed on the poly-electrolyte fibers. In order to derive the electric potential distribution in the membrane, the Debye–Hückel approximation is used to linearize the Poisson–Boltzmann equation, which is further used in hydrodynamic governing equations to investigate the electrokinetic effects in the membrane. The flow domain is divided into two subdomains: the FCL region, governed by the Brinkmann–Forchheimer equation, and the clear fluid region, governed by the Stokes equation. The effect of electroosmotic parameters such as electric double layer (EDL) thickness, thickness ratio parameter, and zeta potential, and the membrane parameters such as viscosity ratio, particle volume fraction, stress-jump parameter, Forchheimer number, and variable permeability parameter are analyzed on the flow profile as well as hydrodynamic quantities of the membrane such as hydrodynamic permeability and the Kozeny constant. It is observed that the increasing thickness of the EDL and equivalent EDL reduce the hydrodynamic permeability of the membrane; however, the membrane becomes more hydrodynamic permeable with the enhancement of the zeta potential.
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    Hydrodynamic permeability of membranes built up by spherical particles covered by porous shells: effect of stress jump condition
    (Springer, 2010) Tiwari, Ashish
    This paper concerns the flow of an incompressible, viscous fluid past a porous spherical particle enclosing a solid core, using particle-in-cell method. The Brinkman’s equation in the porous region and the Stokes equation for clear fluid are used. At the fluid–porous interface, the stress jump boundary condition for the tangential stresses along with continuity of normal stress and velocity components are employed. No-slip and impenetrability boundary conditions on the solid spherical core have been used. The hydrodynamic drag force experienced by a porous spherical particle enclosing a solid core and permeability of membrane built up by solid particles with a porous shell are evaluated. It is found that the hydrodynamic drag force and dimensionless hydrodynamic permeability depends not only on the porous shell thickness, particle volume fraction γ and viscosities of porous and fluid medium, but also on the stress jump coefficient. Four known boundary conditions on the hypothetical surface are considered and compared: Happel’s, Kuwabara’s, Kvashnin’s and Cunningham’s (Mehta–Morse’s condition). Some previous results for the hydrodynamic drag force and dimensionless hydrodynamic permeability have been verified.
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    Hydrodynamic permeability of aggregates of porous particles with an impermeable core
    (Elsevier, 2011-05) Tiwari, Ashish
    A hydrodynamic permeability of membranes built up by porous cylindrical or spherical particles with impermeable core is investigated. Different versions of a cell method are used to calculate the hydrodynamic permeability of the membranes. Four known boundary conditions, namely, Happel's, Kuwabara's, Kvashnin's and Cunningham/Mehta-Morse's, are considered on the outer surface of the cell. Comparison of the resulting hydrodynamic permeability is undertaken. A possible jump of a shear stress at the fluid-membrane interface, its impact on the hydrodynamic permeability is also investigated. New results related to the calculated hydrodynamic permeability and the theoretical values of Kozeny constant are reported. Both transversal and normal flows of liquid with respect to the cylindrical fibers that compose the membrane are studied. The deduced theoretical results can be applied for the investigation of the hydrodynamic permeability of colloidal cake layers on the membrane surface, the hydrodynamic permeability of woven materials.
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    Effect of the magnetic field on the hydrodynamic permeability of a membrane
    (Springer, 2012-07) Tiwari, Ashish
    The present paper concerns the influence of the magnetic field on the permeability of a membrane of solid cylindrical particles covered with porous layer. Here, we have considered the flow along the axis of cylinder and the alignment of uniform magnetic field is assumed to be perpendicular to the axis. The Brinkman equation is used for flow through porous region and Stokes equation is used for flow through clear fluid region. To model flow through assemblage of particles, cell model technique has been used i.e. the porous cylindrical shell is assumed to be confined within a hypothetical cell of same geometry. The stress jump condition has been employed at the fluid-porous interface and all four alternative conditions Happel, Kuwabara, Kvashnin and Mehta-Morse/Cunningham are used at the hypothetical cell. Effect of the Hartmann number on the hydrodynamic permeability of the membrane is discussed
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    Hydrodynamic permeability of biporous membrane
    (Springer, 2013-07) Tiwari, Ashish
    This paper concerns the hydrodynamic permeability of biporous medium built up by porous cylindrical particles located in another porous medium by using cell model technique. It is continuation of the previous work of authors where biporous membrane was built up by porous spherical particles embedded in accompanying porous medium. Four known boundary conditions, namely, Happel’s, Kuwabara’s, Kvashnin’s and Cunningham/Mehta-Morse’s, are considered on the outer surface of the cell. The variation of hydrodynamic permeability of biporous medium (membrane) with viscosity ratio, Brinkman constants, and solid fraction are presented and discussed graphically. Comparison of the resulting hydrodynamic permeability is undertaken. Some previous results for dimensionless hydrodynamic permeability have been verified.
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    Hydrodynamic permeability of a membrane built up by spheroidal particles covered by porous layer
    (Springer, 2017-12) Tiwari, Ashish
    This paper concerns the motion of a viscous steady incompressible fluid through a membrane, where the membrane is built up by impermeable spheroidal particles covered by a porous layer. In this work, we discuss the hydrodynamic permeability of a membrane built up by spheroidal particles. Cell model technique has been used to find the hydrodynamic permeability of the membrane. The emphasis is placed on the hydrodynamic permeability of the membrane and its controlling parameters like the permeability of the porous medium, particle volume fraction, deformation parameters, stress jump coefficient. The dependency of the hydrodynamic permeability of the membrane on the above controlling parameters is discussed graphically. Some previous results for hydrodynamic permeability and drag force are verified.
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    Stokes Flow Through a Membrane Built up by Nonhomogeneous Porous Cylindrical Particles
    (Elsevier, 2019-12) Tiwari, Ashish
    This work deals with the creeping flow of an incompressible viscous fluid through a membrane. It is assumed that the membrane is composed of nonhomogeneous porous cylindrical particles with radially varying permeability enclosing a cavity. The flow within the nonhomogeneous porous medium is governed by the Darcy equation. The flow inside the cavity and outside the nonhomogeneous porous region is governed by the Stokes equations. An analytical solution of the problem is obtained by using the cell model technique. Exact expressions for the drag force acting on the membrane and hydrodynamic permeability of the membrane are derived. The influence of radially varying permeability on flow parameters is considered. The effects of various parameters of the problem on hydrodynamic permeability of the membrane are discussed for four models. Some previous results for hydrodynamic permeability are verified as special limiting cases
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    Creeping flow of micropolar fluid through a swarm of cylindrical cells with porous layer (membrane)
    (Elsevier, 2019-11) Tiwari, Ashish
    The flow of micropolar fluid through a membrane modeled as a swarm of solid cylindrical particles with porous layer using the cell model technique is considered. The flow is directed perpendicular to the axis of the cylinders. Boundary value problem involves traditional conditions of velocities and stresses continuity, no-stress and no-couple stress/no-spin condition on hypothetical cell surface. The problem is solved analytically and the influence of micropolar and porous medium parameters on hydrodynamic permeability of a membrane is investigated.