Dennis A. Siginer

Permeability Measurement Methods in Porous Media of Fiber Reinforced Composites

Accurate measurement of permeability is critical for fluid flow modeling in porous media. Various experimental methods devised to measure permeability as a porous material property in composites are reviewed. Liquid flow and gas flow methods of permeability measurement for in-plane and transverse directions specifically for fiber-reinforced composites are discussed, as well as issues related to these methods and some associated permeability models. Alternative methods of permeability determination based on cross transport phenomenon are reviewed as well. DOI: 10.1115/1.4001047

Analytical and numerical results for the Swift-Hohenberg equation

The problem of the Swift-Hohenberg equation is considered in this paper. Using homotopy analysis method (HAM) the series solution is developed and its convergence is discussed and documented here for the first time. In particular, we focus on the roles of the eigenvalue parameter @a and the length parameter l on the large time behaviour of the solution. For a given time t, we obtain analytical expressions for eigenvalue parameter @a and length l which show how different values of these parameters may lead to qualitatively different large time profiles. Also, the results are presented graphically. The results obtained reveal many interesting behaviors that warrant further study of the equations related to non-Newtonian fluid phenomena, especially the shear-thinning phenomena. Shear thinning reduces the wall shear stress.

Effect of Fiber Sizing — Test Fluid Interaction on the Unsaturated and Saturated Flow in the VARTM Process

The focus of this experimental investigation is the sizing-test fluid interaction reported to result in variable flow behavior in and permeability values for porous media. The flow behavior is studied for Vacuum Assisted Resin Transfer Molding (VARTM). Three types of sizing and three test fluids were chosen for the experiments. Two carbon stitch and two glass stitch bonded fabrics of different tow sizes were used for flow characterization. The present study uses two fluids with the same viscosity for each fabric to determine fluid-sizing interaction. The results show that the permeability values are the same with the fluids of same viscosity. The saturated flow behavior due to the heterogeneous nature of the media is different from the one observed in RTM processes. For VARTM processes the dual scale flow characteristics is not observed for a variety of tow sizes.

Natural Convection in Inclined Two Dimensional Rectangular Cavities

Steady two-dimensional natural convection in fluid filled cavities is numerically investigated. The channel is heated from below and cooled from the top with insulated side walls and the inclination angle is varied. The field equations for a Newtonian Boussinesq fluid are solved numerically for three cavity height based Rayleigh numbers, Ra = 104, 105 and 106, and several aspect ratios. The calculations are in excellent agreement with previously published benchmark results. The effect of the inclination of the cavity to the horizontal with the angle varying from 0° to 180° and the effect of the startup conditions on the flow pattern, temperature distribution and the heat transfer rates have been investigated. Flow admits different configurations at different angles as the angle of inclination is increased depending on the initial conditions. Regardless of the initial conditions Nusselt number Nu exhibits discontinuities triggered by gradual transition from multiple cell to a single cell configuration. The critical angle of inclination at which the discontinuity occurs is strongly influenced by the assumed startup field. The hysteresis effect previously reported is not always present when the calculations are reversed from 90° to 0°. A comprehensive study of the flow structure, the Nu variation with varying angle of inclination, the effect of the initial conditions and the hysteresis effect are presented.

PERMEABILITY MEASUREMENT METHODS IN POROUS MEDIA: A REVIEW

Accurate measurement of Permeability is critical for fluid flow modeling in porous media. Various experimental methods have been devised that measure permeability as a porous material property. These experiments are based most commonly on Darcy’s law. Liquid flow and gas flow methods of permeability measurement for in-plane and transverse directions are detailed. Issues related to these methods are discussed. Some associated permeability models are discussed. Alternative methods of permeability determination based on cross transport phenomenon are presented.Copyright

Graetz Problem in Ducts of Circular and Some Non-Circular Cross-Sections With Viscoelastic Fluids

An investigation of heat transfer with viscoelastic fluids in straight pipes of circular and some non-circular cross-sections is carried out. The influence of the rheological parameters on heat transfer enhancement with viscoelastic fluids in the entrance region of tube flow is investigated with negligible axial heat conduction and viscous dissipation. Numerical simulations are conducted with constant wall heat flux for the Graetz problem using the finite element based software Polyflow for viscoelastic fluids of the simplified Phan-Thien Tanner (SPPT) type. It is found that increasing the fluid elasticity, for all cross-sections, raises the normalized heat transfer coefficient for relatively low elasticity values but for high level of fluid elasticity the normalized heat transfer coefficient decreases.Copyright

Analysis of Plug Zones in Steady Flow in Undulating Channels

Undulating channels are important in several industrial applications related to heat transfer and also as a modeling resource for complex flow through pores or fibers. In this paper, flow of a Bingham plastic in an undulating channel is studied. An analytical model is developed which allows to determine the regions in the flow where solid (plug) or quasisolid behavior appears. The parameters considered are the dimensionless yield stress, the channel amplitude and the Reynolds number. A variety of cases are presented, in which the characteristics of the flows are described. The main results are presented by means of the streamlines, isobars, constant shear stress lines, isovelocities, and velocity profiles. Good consistency if found among all variables analyzed.Copyright

Conduit Flow Control Through Magnetorheology

In this paper it is addressed the problem of flow stability in conduits when an essentially steady flow is perturbed by undesirable fluctuations of the pressure gradient. This problem may arise when working conditions in conduit systems induce sporadic or permanent oscillations of the pressure at the end of some conduits. In cases where the flow occurs in closed circuits and it is important to reduce or eliminate flow fluctuations, it is possible to impose flow control by making use of the magnetorheological properties of some fluids. An analytical model is presented in which the working fluid is assumed to be affected by a magnetic field whose strength is proportional to the instantaneous rate of flow. In this way, it is shown that oscillatory perturbations of an otherwise constant pressure gradient can be damped away through the synchronized oscillations of the yield stress generated in the fluid by the magnetic field. The paper includes the solution of the analytical model and several examples of applications.Copyright

Resonance modelling and control in structures by means of magnetorheological dampers

Many structures such as automobile bodies, bridges and buildings are subjected to external forces due to the nature of the environment in which they exist. When the external excitation frequency is similar to the structure’s natural frequency a resonance effect is generated, increasing the energy and the amplitude of the oscillation, often causing catastrophic situations. This paper presents a method to decrease such resonant oscillations using magnetorheological dampers.© 2010 ASME

Laminar Flow Model in Ducts of Circular Section With Arbitrary Axial Variation

Laminar flow inside a circular duct of variable section in the axial direction is modeled, assuming that the working fluid is Newtonian, incompressible, with laminar flow, a permanent state, and constant properties. The results describe the behavior of the stream function, the velocity field, and the pressure field, and graphic results are presented for each of those functions. The method used to solve the problem makes use of regular perturbations around the shape factor e parameter. This research can be used for the design of new technological devices important to industry, optimizing processes in which fluids are transported, energy is transferred, etc.© 2010 ASME