Effects of rough boundary and nonzero boundary conditions on the lubrication process with micropolar fluid (original) (raw)
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Thermal Science
This paper presents the theoretical analysis of comparison of porous structures on the performance of a slider bearing with surface roughness in micropolar fluid film lubrication. The globular sphere model and Irmay's capillary fissures model have been subject to investigations. The general Reynolds equation which incorporates randomized roughness structure with Stokes micropolar fluid is solved with suitable boundary conditions to get the pressure distribution, which is then used to obtain the load carrying capacity. The graphical representations suggest that the globular sphere model scores over the Irmay's capillary fissures model for an overall improved performance. The numerical computations of the results show that, the act of the porous structures on the performance of a slider bearing is improved for the micropolar lubricants as compared to the corresponding Newtonian lubricants.
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.
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...
Tribology Online, 2022
In this paper, an investigation has been made to study the dynamic characteristics of porous inclined slider bearing with rough surface lubricated with micropolar fluid lubricant. On the basis of Eringen's micro-continuum theory, the Reynolds type equation of porous slider bearing is derived by considering rough surface and squeezing action to evaluate dynamic characteristics of slider bearing. Perturbation method has been used for detailed analysis. Reynolds type equations are obtained for steady performance and perturbed characteristics. The solutions of these equations are obtained. According to the results, an increase (decrease) in the load carrying capacity, dynamic stiffness and damping coefficient are observed for the negatively (positively) skewed surface roughness.
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]
MICROPOLAR FLUID LUBRICATION OF FINITE PARTIAL ROUGH POROUS JOURNAL BEARINGS WITH SQUEEZE EFFECT
In this paper, the lubrication theory for squeezing with micropolar fluids in smooth surfaces has been advanced to analyze the effects arising from roughness consideration using the stochastic approach. Basing on the Christensen's stochastic model, the stochastic generalized Reynolds equation is deduced. The Christensen stochastic theory of hydrodynamic lubrication of rough surface is used to study the effect of two types of surface roughness on the squeeze film characteristics of a finite partial porous journal bearing with micropolar fluid. It is assumed that, the roughness asperity heights are small compared to the film thickness. The film pressure distribution equation is numerically solved by using the conjugate gradient method of iterations. According to the results, the micropolar fluid effects can raise the film pressure of the lubricant fluid, improve the load –carrying capacity and squeezing effect. The surface roughness effect in the influence of longitudinal or transverse to the journal bearing is in reverse trend.
Effect of slip/no-slip on finite slider bearing using non-Newtonian micropolar fluid
2018
Load Slip Pressure Micropolar fluid Hydrodynamic In this paper, the modified Reynolds equation of finite slider bearing lubricated with micropolar fluid is numerically solved for the computational aspects of the bearings. The finite difference scheme has been employed to solve the governing equations. The effect of micropolar parameter and slip parameter is investigated on slider bearing. For investigating the effect of slip boundary on the pressure distribution in sliding surface is numerically presented in the Reynolds model. The two-dimensional modified Reynolds equation can predict the performance of lubrication process with boundary slip in sliding contact which can be seen by the obtained results. The pressure and load capacity are displayed graphically. The pressure and load carrying capacity is lesser for slip case as compared to no slip case.
The contributions of microrotation of lubricant molecules in a thin film journal bearing
Acta Mechanica, 2002
Characteristics of a journal bearing were computed for thin film lubrication accounting for microrotation of the lubricant molecules using both the half-Sommerfeld and Reynolds boundary conditions. Although the Reynolds boundary conditions produced higher pressure and loads, the effects of microrotation studied by both schemes showed similar trends. Primary characteristics that effect the contributions of microrotation to the load carrying capacity of the journal bearing were identified. These characteristics were varied and their effects on the load capacity of the journal bearing are shown.
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.