ELEMENT FREE GALERKIN SIMULATION OF UNSTEADY MICROPOLAR SQUEEZE FILM FLOW OF A BIOLOGICAL LUBRICANT (original) (raw)
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Effect of micropolar fluids on the squeeze film elliptical plates
Journal of Physics: Conference Series, 2018
This paper elaborates on the theoretical analysis of squeeze film characteristics between elliptical plates lubricated with non-Newtonian micro-polar fluid on the basis of Eringen's micropolar fluid theory. The modified Reynold's equations governing flow of micro-polar fluid is mathematically derived and the outcome reveals distribution of film pressure which determines the dynamic performance characteristics in terms of load and squeezing time for various values of coupling number and micro structure size parameter. Based on the results reported, The influence of non-Newtonian micropolar fluids is examined in enhancing the time of approach and load carrying capacity to the case of classical Newtonian lubricant.
The transient squeezing flow of a magneto-micropolar biofluid in a noncompressible porous medium intercalated between two parallel plates in the presence of a uniform strength transverse magnetic field is investigated. The partial differential equations describing the twodimensional flow regime are transformed into nondimensional, nonlinear coupled ordinary differential equations for linear and angular momentum (micro-inertia). These equations are solved using the robust Homotopy Analysis Method (HAM) and also numerical shooting quadrature. Excellent correlation is achieved. The influence of magnetic field parameter (Ha), micropolar spin gradient viscosity parameter (ÀÞ and unsteadiness parameter (S) on linear and angular velocity (micro-rotation) are presented graphically, for specified values of the micropolar vortex viscosity parameter (R), Darcy number (Da i.e. permeability parameter) and medium porosity parameter ("Þ. Increasing magnetic field (Ha) serves to decelerate both the ¶ Corresponding author.
On The Lubrication of a Rotating Shaft with Incompressible Micropolar Fluid
Topical Problems of Fluid Mechanics 2020, 2020
In this work, we investigate the lubrication process of a slipper bearing. The slipper bearing consists of two coaxial cylinders in relative motion, where an incompressible micropolar fluid (lubricant) is injected in a thin gap between them. We compute the asymptotic approximation of the solution to the governing micropolar system as a power series in terms of the small parameter ε representing the thickness of the shaft. The proposed approximation is given in the explicit form, allowing us to clearly observe the effects of the micropolar nature of the fluid.
Magnetohydrodynamic Micropolar Fluid Squeeze Film Lubrication between Stepped Porous Parallel Plates
Indian journal of science and technology, 2022
Objectives: The primary goal of this paper is to study the influence of MHD and micropolar fluid on the squeeze film lubrication between stepped porous parallel plates. Method: The non-Newtonian micropolar fluid MHD Reynolds type equation is derived by considering the flow of micropolar fluid in the porous matrix as described by Darcy's law, as well as microstructure additives and magnetic effects associated with the magnetization of the fluid. The numerical solutions are presented graphically for the MHD squeeze film characteristics for various values of coupling number parameter, characteristic material length, and magnetic Hartmann number. Findings: According to the results, the micropolar fluid and the magnetic effects significantly influence the squeeze film characteristics. Comparing the MHD micropolar fluid impact on the squeeze film lubrication with the corresponding Newtonian and non-magnetic cases, we observe that there is a significant increase in the approaching time and the load-carrying capability. The increase in the step height decreases the squeezing film time. Novelty: The original research was conducted on the magneto-hydrodynamic micropolar fluid squeeze film lubrication between stepped porous parallel plates which has not been studied so far. The effect of applied magnetic field is to enhance the load carrying capacity and delayed time of approach which are the most desirable characteristics for improving the bearing performance.
Tribology Online
In this paper, combined effects of piezo-viscous dependency and surface roughness on the squeeze film characteristics of non-Newtonian micropolar fluid in conical bearings are presented. On the basis of Christensen's theory, two types of one dimensional structure, the longitudinal roughness and transverse patterns are considered. The stochastic modified Reynolds equation for these two types of roughness patterns is derived for micropolar fluid by taking into account variation of viscosity with pressure. Through a small perturbation technique, the analytical approximate solution for the mean fluid film pressure, load carrying capacity and squeeze film time is obtained. According to the results, the combined effects of non-Newtonian and viscosity pressure dependency provide an enhancement in the load carrying capacity and lengthen the response time for both types of roughness patterns as compared to the classical iso-viscous Newtonian lubricant case. On the whole, the squeeze film characteristics of conical bearings is improved especially for higher values of coupling parameter and viscosity parameter.
Journal of Plastic Film & Sheeting, 2018
The theoretical model of roll coating onto a moving sheet is developed based on micropolar fluid constitutive equations and lubrication approximation. Closed form expressions for velocity, microrotation and pressure gradient are obtained. Runge-Kutta method is used to calculate the engineering quantities of interest such as, pressure, roll-separating (load-carrying) force and power input. The separation point is numerically calculated using Newton’s iterative method together with generalized Leibniz rule. The effects of involved parameters on the pressure gradient, velocity, pressure and other mechanical quantities are displayed through various graphs. Extreme pressure is observed in the nip region for larger coupling numbers and microrotation parameters. This leads to increased load-carrying force and power input for micropolar fluid when compared to a Newtonian fluid. Moreover, the separation point decreases from its Newtonian value with increasing [Formula: see text]
Symmetry
Motivated by the lubrication processes naturally appearing in numerous industrial applications (such as steam turbines, pumps, compressors, motors, etc.), we study the lubrication process of a slipper bearing consisting of two coaxial cylinders in relative motion with an incompressible micropolar fluid (lubricant) injected in the thin gap between them. The asymptotic approximation of the solution to the governing micropolar fluid equations is given in the form of a power series in terms of the small parameter ε representing the thickness of the shaft. The regular part of the approximation is obtained in the explicit form, allowing us to acknowledge the effects of fluid’s microstructure clearly through the presence of the microrotation viscosity in the expressions for the first-order velocity and microrotation correctors. We provide the construction of the boundary layer correctors at the upper and lower boundary of the shaft along with the construction of the divergence corrector, a...
Effect of concentration dependence of viscosity on squeeze film lubrication
Zeitschrift für Naturforschung A, 2020
The influence of concentration of solute particles on squeeze film lubrication between two poroelastic surfaces has been analyzed using a mathematical model. Newtonian viscous fluid is considered as a lubricant whose viscosity varies linearly with concentration of suspended solute particles. Convection-diffusion model is proposed to study the concentration of solute particles and is solved using finite difference method of Crank–Nicolson scheme. An iterative procedure is used to get the solution for concentration, pressure and velocity components in film region. It has been observed that load carrying capacity decreases as the concentration of solute particles in the fluid film decreases. Further, the concentration of suspended solute particles decreases as the permeability of the poroelastic plate increases and these results may be useful in understanding the mechanism of human joint.
Soft Elasto-Hydrodynamic Lubrication
Tribology Letters, 2010
Biocompatible microgels have been demonstrated to act as excellent lubricants, however, the influence of the continuum on their overall mechanical performance has been neglected so far. In this work, the mechanical performance of colloidal whey protein microgels (hydrodynamic diameter B100 nm measured using dynamic light scattering and atomic force microscopy) of different rigidity dispersed in Newtonian (buffer and corn syrup) or complex non-Newtonian fluids (xanthan gum) is investigated for the first time via rheology and soft tribology. Dispersions of both soft microgels (G 0 B 100.0 Pa) and hard microgels (G 0 B 10.0 kPa) were observed to act as thickeners in buffer as well as in low viscosity corn syrup and correspondingly reduced the friction, latter decreased as a function of the increased rigidity of the microgels. Differently, in high viscosity continuum, the microgels acted as thinning agents and increased the friction. In the lubrication limit, microgels in buffer or corn syrup behaved as Newtonian fluids with effective viscosity corresponding to their second Newtonian plateau value (Z N). However, the lubrication performance of the microgels dispersed in the complex fluid (xanthan gum) could not be described quantitatively by Z N. For the low viscosity xanthan gum, the microgels had no influence on friction. Nevertheless, for the high viscosity counterparts, the soft microgels acted as thinning agents whilst the hard microgels accelerated the onset of elastohydrodynamic regime. This study demonstrates that microgels act as viscosity modifiers directly influencing the tribological performance, depending upon a subtle interplay of rheological properties of the particles and continuum.
In the present study, the performance of squeeze films between parallel elliptical plates lubricated by non-Newtonian couplestress ferrofluid has been investigated using transverse magnetic field. Based on the Shliomis' ferrohydrodynamic model along with stroke micro-continuum theory the Reynolds' expression was derived for engineering application. Furthermore, the solution for pressure distribution has been obtained in the analysis. Results shows that the non ferrofluid characterized the squeeze film operating with a higher standard of Langevin parameter and volume concentration of magnetic particles enhances the load capacity and maximize the squeeze time of the elliptical plate compared to Newtonian and non-ferrofluid case.