Effect Of Micropolar Parameters Research Articles

Steady-state performance of elliptical contact lubricated with micropolar fluids

In this work, the numerical investigation is done for the steady-state performance of elliptical contacts lubricated with micropolar fluids. The Eringen’s micro-continuum theory is applied to deduce the modified Reynolds equation for micropolar fluids. The modified Reynolds equation is discretized by the finite difference technique and evaluated by a multigrid technique for finding the steady-state pressure distribution; simultaneously, the elasticity equation is solved with the multilevel multi-integration method. The numerical solution is achieved under isothermal conditions and considering the exponential variation of viscosity with pressure. The effect of micropolar parameters, i.e. nondimensional characteristics length defines the molecular length of the blended additives, and coupling number measures the coupling between the angular and linear momentum of molecules, and operating parameters are studied. Owing to the analysis, the pronounced effect of the micropolar parameters on the elastohydrodynamic lubrication of elliptical contacts is observed and which cannot be avoided. Lubricants added with solid additives and coupling between linear and angular momentum improved the overall film thickness and pressure and enhanced the load-carrying capacity. Also, a nominal rise in the traction coefficient is noticed, but this increase in the traction coefficient is quite less when compared to Newtonian fluids.

Nonlinear transient analysis of hole-entry journal bearing with constant flow of micropolar fluids

The present work deals with study and analysis of a symmetric hybrid journal bearing compensated with constant flow valve restrictor operating with micropolar fluid from stability point of view. The effect of micropolar parameters on the stability of this journal bearing system is presented on the basis of nonlinear transient model. Finite element method has been used to solve modified Reynolds’ equation for the flow of micropolar fluid through the bearing. Computations are done for the static and dynamic characteristics of hole-entry hybrid journal bearing system. The stability characteristics in terms of critical mass of journal, threshold speed, and frequency of whirl are obtained for journal bearing system operating with Newtonian and micropolar fluids and are compared together. Paths of the journal center in the form of trajectories have also been plotted using the journal center coordinates obtained after solving nonlinear equation of motion by fourth-order Runge–Kutta method to find the stability margin of the considered bearing configuration more precisely and easily. Results indicate that micropolar effect causes significant increase in stability margin of the hybrid journal bearing system especially at higher loads. The results also indicate that lubricant flow through the bearing and type of lubricant should be decided in an appropriate manner for the stability of the constant flow valve compensated hybrid journal bearing system.

NUMERICAL STUDY OF MIXED CONVECTION FLOW OF A MICROPOLAR FLUID TOWARDS PERMEABLE VERTICAL PLATE WITH CONVECTIVE BOUNDARY CONDITION

In this article, the mixed convective flow of a micropolar fluid along a permeable vertical plate under the convective boundary condition is analyzed. The scaling group of transformations is applied to get the similarity representation of the system of partial differential equations of the problem and then the resulting equations are solved by using Spectral Quasi-Linearisation Method. This study reveals that the dual solutions exists for certain values of mixed convection parameter. The outcomes are analyzed with dual solutions in detail. Effects of micropolar parameter, Biot number and suction/injection parameters on different flow profiles are discussed and depicted graphically.

Performance characteristics of constant flow valve compensated conical multirecess hybrid journal bearing under micropolar lubrication

This paper presents the theoretical study on the effect of micropolar parameters of the fluid and the semi-cone angle on the performance characteristics of a conical multirecess hybrid journal bearing under micropolar lubrication compensated with constant flow valve. The numerical solution of the modified Reynolds equation for micropolar fluid flow on the conical surface has been done by using finite element method using Galerkin's technique along with the necessary boundary conditions and iterative scheme. The performance characteristics have been presented for a wide range of the semi-cone angle and the restrictor design parameter of the conical hybrid journal bearing system operating under Newtonian and micropolar lubrication. The study suggests that the semi-cone angle of the bearing, constant flow valve restrictor and micropolar parameters significantly influence the performance characteristics of conical bearing. With increase in semi-cone angle of bearing the direct stiffness, damping coefficients and the stability margin have been observed to increase significantly.

A Comparative Elastohydrostatic Analysis of CFV- and Capillary-Compensated Multirecess Hydrostatic/Hybrid Journal Bearing Operating with Micropolar Lubricant

A comparative study on the performance characteristics of the flexible multirecess hydrostatic journal bearing system with constant flow valve and capillary restrictors has been presented considering the effect of micropolar parameters. The modified Reynolds equation for the flow of micropolar lubricant through the bearing has been solved using finite element method, and the resulting elastic deformation in the bearing shell has been determined iteratively. The results indicate that the micropolar parameters of the lubricant affect the performance of the flexible multirecess hydrostatic journal bearing system quite significantly.

Transient Analysis of Forced Convection Along a Wavy Surface in Micropolar Fluids

Numerical results for transient laminar-forced convection along a wavy surface in micropolar fluids are presented. A simple coordinate transformation is employed to transform the complex wavy surface to a flat plate, and the obtained nonsimilarity boundary layer equation is solved numerically by the spline alternating-direction implicit method. The effects of micropolar parameter and wavy geometry on the velocity and temperature fields are examined. The transient skin friction and transient local and averaged heat-transfer rates decrease with time. Their axial distributions have a frequency equal to the frequency of the wavy surface, but their crests and troughs do not occur just at the crests and troughs of the wavy surface. The amplitudes of the transient local skin-friction coefficient and the transient local Nusselt number tend to increase as the wavy length and the wavy amplitude-wavelength ratio increases. Furthermore, the transient Nusselt number of a micropolar fluid is smaller than that of a Newtonian fluid everywhere, whereas the transient local skin-friction coefficient of a micropolar fluid is larger than that of a Newtonian fluid just near the leading edge

A thermal instability problem in a rotating micropolar fluid

An analysis of the thermal stability problem of an incompressible, rotating, micropolar fluid heated from below is given. consideration is also given to the possibility of oscillatory convection. It is found that, depending upon the values of various micropolar parameters and the low values of the Taylor number, the rotation has a stabilizing effect. the effect of micropolar parameters on the condition whether stationary convection or oscillatory convection will prevail is briefly pointed out.

Numerical solution of combined convective heat transfer of micropolar fluid in an annulus of two vertical pipes

The problem of free and forced convective heat transfer of micropolar fluid in an annulus of two vertical pipes has been studied by applying Runge—Kutta—Merson method. It has been found that, when the temperature of the pipes decreases with height, the presence of micropolar elements delay the onset of instability. On the other hand, when the temperature increases with height it has been noticed that microrotation enhances the back flow. Effect of micropolar parameters and Rayleigh number on heat transfer are also discussed in detail.