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Pore-Scale Modeling of Navier-Stokes Flow in Distensible Networks and Porous Media
Get PDFIn this paper, a pore-scale network modeling method, based on the flow continuity residual in conjunction with a Newton-Raphson non-linear iterative solving technique, is proposed and used to obtain the pressure and flow fields in a network of interconnected distensible ducts representing, for instance, blood vasculature or deformable porous media. A previously derived analytical expression correlating boundary pressures to volumetric flow rate in compliant tubes for a pressure-area constitutive elastic relation has been used to represent the underlying flow model. Comparison to a preceding equivalent method, the one-dimensional Navier-Stokes finite element, was made and the results were analyzed. The advantages of the new method have been highlighted and practical computational issues, related mainly to the rate and speed of convergence, have been discussed
Large Eddy Simulation of Three Dimensional Impinging Jets
Get PDFThis paper presents a large eddy simulation of three dimensional vertically impinging jet on a horizontal plate. The air impinging jet was simulated using the perturbed method based on a high vortex number in the jet inlet for different ranges of Reynolds number Re= 6000, 8000, 10000, 12000, 14000 and for the same distance between the jet and the impinging plate. The effect of the Reynolds number of the air jet impinging on a horizontal plate was studied; the study showed that the vorticity magnitude is increased with the increasing of the Reynolds number. The turbulent flow jet was decomposed into three principal regions: the free jet region, the impinging point region and the wall jet region. The increase of the jet Reynolds number has a strong effect on the turbulent characteristics of the flow near the wall plate
Comparison of Four Multiscale Methods for Elliptic Problems
Get PDFFour representative multiscale methods, namely asymptotic homogenization method (AHM), heterogeneous multiscale method (HMM), variational multiscale (VMS) method and multiscale finite element method (MsFEM), for elliptic problems with multiscale coefficients are surveyed. According to the features they possess, these methods are divided into two categories. AHM and HMM belong to the up–down framework. The feature of the framework is that the macroscopic solution is solved first with the help of effective information computed in local domains, and then the multiscale solution is resolved in local domains using the macroscopic solution when necessary. VMS method andMsFEM fall in the uncoupling framework. The feature of the framework is that the multiscale solution in the global domain is resolved directly making use of special functions defined in the macroscopic mesh. The cost of these multiscale methods is compared and their application to a functionally graded material is illustrated. Moreover, the manner to resolve multiscale solutions in AHM and HMM is compared, and it is found that AHM and HMM provide similar multiscale solutions
Ambarzumyan Type Theorem For a Matrix Valued Quadratic Sturm-Liouville Problem
Get PDFIn this study, Ambarzumyan’s theorem for quadratic Sturm-Liouville problem is extended to second order differential systems of dimension d ≥ 2. It is shown that if the spectrum is the same as the spectrum belonging to the zero potential, then the matrix valued functions both P(x) and Q(x) are zero by imposing a condition on P(x). In scaler case, this problem was solved in [Koyunbakan, Lesnic and Panakhov (2013)]
Filamin: A Structural and Functional Biomolecule with Important Roles in Cell Biology, Signaling and Mechanics
Get PDFFocal adhesions are the immediate sites of the cell’s adhesive interaction with the extracellular matrix and as such play a key role in mechanosensing and mechanotransduction at the edge of the cell interface with its surrounding microenvironment. A multitude of proteins orchestrate this mechanochemical communication process between the cell and its outside world. Filamin is a member of focal adhesion protein machinery that also plays a key role in regulating and bundling the acting filament network. A brief review is presented here on filamin and its important protein partners with the aim to shed light on the role of filamin’s protein-protein interaction network in cell mechanobiology
Forced-Mixed Convection Transition of a Buoyant Axisymmetric Jet with Variable Properties
Get PDFThis paper describes the transition from forced to mixed convection in a jet flow with variable properties. The classical laminar layer analysis is extended by taking into account the dependence of physical properties on temperature. The related model relies on the assumption that the variations of Prandtl number and specific heat at constant pressure are sufficiently small to be neglected. A second-order finite-difference numerical method based on a staggered grid is used to analyze transition, hydrodynamic and heat transfer phenomena in the jet. The dimensionless control parameter, Λ = T0/T∞, is limited to values less than 1. It is found that the variation of physical properties with temperature has a significant effect on jet flow velocity, whereas this dependence has an almost negligible influence on the expansion characteristics of the flow
Transient Electrohydrodynamics of a Liquid Jet: Evolution of The Flow Field
Get PDFComputational studies are performed to explore the underlying physics behind the evolution of the flow field in an around a liquid jet that is immersed in another liquid and is exposed to a uniform electric field. Here the focus is on finite Reynolds and O(1) Ohnesorge number flows. This is achieved by solving the full Navier-Stokes and electric field equations using a front tracking/finite difference technique in the framework of Taylor's leaky dielectric theory. It is shown that the evolution of the flow field is determined by the relative magnitude of the ratio of the electric conductivity R = σi/σo and permittivity S = εi/εo, where the subscripts i and o denote the fluid inside and outside of the jet. For fluid systems for which R > S or S > (1/3)(R2+R+1) the flow is established by formation of four vortices inside the jet that gradually grow outward until their growth is limited by the jet interface. On the other hands, for fluid systems for which R 2+R+1) the flow evolves through evolution of four vortices that are formed in the ambient fluid and gradually penetrate into the jet until they are confined within the jet. Examination of the electrohydrodynamics of the jets in creeping flows leads to similar observations, and using the closed form analytical solution for these flows the computational and analytical results are justified
Effects of Internal Heat Generation and Variable Fluid Properties on Mixed Convection Past a Vertical Heated Plate
Get PDFHeat and Mass transfer from a vertical heated plate embedded in a sparsely packed porous medium with internal heat generation and variable fluid properties like permeability, porosity and thermal conductivity has been investigated numerically. In particular, the governing highly non-linear coupled partial differential equations are transformed into a system of ordinary differential equations with the help of similarity transformations and solved numerically by using a shooting algorithm based on a Runge-Kutta-Fehlberg scheme and a Newton Raphson method (to obtain velocity, temperature and concentration distributions). The heat and mass transfer characteristics are analyzed and related physical aspects are discussed in detail to interpret the effect of the various significant problem parameters. The results show that the buoyancy ratio number, Prandtl number Pr, Schmidt number Sc and other parameters play an important role. The obtained results are compared with previously published works and they are found to be in very good agreement. The effects of the considered parameters on the local skin friction coefficient (viscous drag), Nusselt number (rate of heat transfer) and Sherwood number (rate of mass transfer) are also discussed
Effective Surface Susceptibility Models for Periodic Metafilms Within the Dipole Approximation Technique
Get PDFThe most important surface susceptibility models for the electromagnetic characterization of periodic metafilms, based on the dipole approximation method, are systematically analyzed in this paper. Specifically, two well-known techniques, which lead to a set of local effective surface parameters, are investigated along with a new dynamic non-local modeling algorithm. The latter formulation is properly expanded, in order to be applicable for any arbitrary periodic metafilm, irrespective of its way of excitation. The featured schemes are then directly compared toward their ability to efficiently predict the reflection and transmission properties of several lossless and lossy metafilms. Their outcomes are carefully verified through an assortment of numerical simulations, while novel physical insights of the observed phenomena and diverse implementation aspects of the models are extensively discusse
Characteristics of a Single I-shaped Slitted Zeroth-Order Resonance Mushroom Antenna based on Metamaterials
Get PDFThe broadband design of a metamaterials-based zeroth-order resonance (ZOR) mushroom antenna with an I-shaped slit is presented and experimentally studied. The presented metamaterials-based antenna uses a unit cell based on a composite right/left handed (CRLH) transmission line and can provide a ZOR frequency. By designing the I-shaped slot resonance frequency adjacently to the ZOR frequency, the presented antenna can achieve a 10-dB bandwidth enhancement of roughly 7 times with respect to a conventional rectangular-shaped mushroom structure