Inertia effects in circular squeeze films containing a central air bubble
TL;DR: An analysis of the laminar squeezing flow of an incompressible Newtonian fluid between parallel circular plates containing a single central air bubble in the inertial flow regime is presented in this article, in which a successive approximation technique is used to account for fluid inertia effects.
About: This article is published in Fluid Dynamics Research.The article was published on 2000-03-01. It has received 4 citations till now. The article focuses on the topics: Lubrication theory & Laminar flow.
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TL;DR: In this article, the shape and extent of the core for the case of sinusoidal squeeze motion has been determined numerically for various values of the Bingham number, Reynolds number and for various amplitudes of squeeze motion.
Abstract: Lubricants with variable viscosity are assuming importance for their applications in polymer industry, thermal reactors and in biomechanics. With the bearing operations in machines being subjected to high speeds, loads, increasing mechanical shearing forces and continually increasing pressures, there has been an increasing interest to use non-Newtonian fluids characterized by an yield value. The most elementary constitutive equation in common use that describes a material which yields is that of Bingham fluid. In the present work, the problem of a circular squeeze film bearing lubricated with Bingham fluid under the sinusoidal squeeze motion has been analyzed. The shape and extent of the core for the case of sinusoidal squeeze motion has been determined numerically for various values of the Bingham number. Numerical solutions have been obtained for the bearing performances such as pressure distribution and load capacity for different values of Bingham number, Reynolds number and for various amplitudes of squeeze motion. The effects of fluid inertia, non-Newtonian characteristics, and the amplitudes of squeeze motion on the bearing performances have been discussed.
7 citations
Cites background from "Inertia effects in circular squeeze..."
...The effects of fluid inertia forces and non-Newtonian characteristics of lubricants in the squeeze film bearings have been examined by several investigators, (Tichy and Winer [8], Covey and Stanmore [2], Gartling and Phan-Thien [4], Donovan and Tanner [7], Huang et al. [6], Usha and Vimala [9]) but there are few papers attempting to describe the combined effects of fluid inertia forces and non-Newtonian characteristics of lubricants (Elkough [3], Batra and Kandasamy [1]) ....
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...[10] R. Usha and P. Vimala, Curved squeeze film with inertial effects-energy integral approach....
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...With sinusoidal squeeze motion, Usha and Vimala [10] have applied the energy integral approach to find the behavior of curved squeeze film bearing using a Newtonian lubricant....
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...[9] R. Usha and P. Vimala, Inertia effects in circular squeeze films containing a central air bubble....
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...[6], Usha and Vimala [9]) but there are few papers attempting to describe the combined effects of fluid inertia forces and non-Newtonian characteristics of lubricants (Elkough [3], Batra and Kandasamy [1]) ....
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TL;DR: In this article, the performance of the bearing by considering the combined effects of fluid inertia forces and non-Newtonian characteristic with Bingham fluid as lubricant in an externally pressurized converging circular thrust bearing is analyzed.
Abstract: Thrust bearing are innately developed to withstand axial load. When the bearing is subjected to high speed operations, heavy load, high stiffness etc., suggesting a change in the design of the bearing plays a vital role in its performance. Friction is developed between the circular plates while the bearing operates. To reduce this friction, the bearing is lubricated with lubricants such as mineral oil, greases etc., Generally, lubricants are classified into two types that is Newtonian and non-Newtonian. However, non-Newtonian fluids characterized by an yield value such as Bingham, Casson and Herschel Bulkley, are attracting the tribologists, at present. And also, the study of fluid inertia on thrust bearing is required to optimize the performance of the bearings. In this investigation, we have ventured to analyze the performance of the bearing by considering the combined effects of fluid inertia forces and non-Newtonian characteristic with Bingham fluid as lubricant in an externally pressurized converging circular thrust bearing. Such studies will be useful in the design of the bearing for the optimum performance using the appropriate lubricant in various machineries operating in an extreme condition in the industries. Averaging the inertia terms over film thickness and defining a modified pressure gradient, the rheodynamic lubrication equation containing inertia terms has been analyzed. Using the appropriate boundary conditions and considering externally pressurized flow in narrow clearance between two converging discs is symmetric w.r.t r and z axis, the velocity distributions, the modified pressure gradient and thereby the film pressure and the load capacity of the bearing have been obtained numerically for different values of Bingham number, Reynolds number and angle of convergence. In addition to that, the effects of the inertia forces, non-Newtonian characteristics and angle of convergence on the bearing performances have been discussed.
1 citations
Cites background from "Inertia effects in circular squeeze..."
...Usha and Vimala discussed inertia effects in a circular squeeze film bearing containing central air bubbles (Usha and Vimala, 2000)....
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TL;DR: In this paper, the combined effects of fluid inertia and viscous forces have been investigated theoretically in an externally pressurized thrust bearing with circular ge- ometry using Herschel-Bulkley fluid as lubricant.
Abstract: The combined effects of fluid inertia and viscous forces of a Herschel-Bulkley lubricant in an externally pressurized thrust bearing with circular geometry have been analyzed theoretically. Although the researchers of the past, laid out a foundation for the hydrodynamic lubrication, modern researchers intend to use non-Newtonian fluids characterized by a yield-value, such as Bingham, Casson and Herschel-Bulkley fluids as lubricants. More over, Tribologists emphasize a fact that in order to analyze the performance of the bearings adequately, it is necessary to consider the combined effects of fluid inertia and viscous forces of non-Newtonian lubricants. Therefore, in this research article, the combined effects of fluid inertia and viscous forces have been investigated theoretically in an externally pressurized thrust bearing with circular ge- ometry using Herschel-Bulkley fluid as lubricant. The shape and extent of the core, along the radius, have been determined numerically for various values of the Herschel-Bulkley number and the power-law index. Using the appropriate boundary conditions, the velocity distributions in the flow and the core regions have been obtained. By considering the equilibrium of an element of the core in the fluid, the modified pressure gradient has been evaluated and thereby the film pressure and the load capacity of the bearing have been obtained numerically for different values of Reynolds number, Herschel-Bulkley number and power-law index. The effects of the inertia forces and the non-Newtonian characteristics of the lubricant, on the bearing performances have also been discussed.
1 citations
Cites background from "Inertia effects in circular squeeze..."
...Usha and Vimala[19] have discussed about inertia effects in circular squeeze films containing a central air bubble....
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...[19] R. Usha and P. Vimala., “Inertia effects in a circular squeeze films containing a central air bubble”....
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TL;DR: In this article, a lumped-parameter dynamic model for an enclosed incompressible squeeze film with a central gas bubble has been derived, and closed-form expressions for the lumpedparameter mass and damping coefficients caused by liquid motion were derived.
Abstract: A lumped-parameter dynamic model for an enclosed incompressible squeeze film with a central gas bubble has been derived. A new approach was applied to derive closed-form expressions for the lumped-parameter mass and damping coefficients caused by liquid motion. It was assumed that plate motions were small and the fluid behaved as a continuum. The values of the lumped-parameter mass and damping were found to depend on the aspect ratio and nondimensional squeeze-film thickness. The nondimensional thickness was given by the ratio of the actual squeeze-film thickness to the viscous penetration depth of the liquid. A nondimensional squeeze-film thickness of a value of 5 was found to divide between categories of thick and thin incompressible squeeze films. Amplification of the liquid mass and damping over and above squeeze films open to the atmosphere at the edges was found. The amplification was attributed to converging flow caused by enclosed boundaries. Comparisons between the lumped-parameter model predictions and finite-element computations showed a surprising degree of accuracy for the lumped-parameter model despite large liquid velocities in the squeeze film.
1 citations
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TL;DR: In this article, the effects of an air bubble on the Newtonian squeeze film characteristics between two circular parallel plates with sinusoidal relative motion were theoretically investigated by considering the fluid film inertia effects.
Abstract: In this paper, the effects of an air bubble on the Newtonian squeeze film characteristics between two circular parallel plates with sinusoidal relative motion are theoretically investigated by considering the fluid film inertia effects. In the derivation of the lubrication equation, a single central air bubble of a cylindrical shape is considered. Approximating the momentum equation governing the squeeze film flow by the mean value averaged across the film thickness and assuming an ideal gas under isothermal condition for an air bubble, a nonlinear differential equation for the bubble radius is obtained. The nonlinear differential equation is solved by the Runge-Kutta-Gill method, and then the squeeze film force is determined. Moreover, the analytical solutions for the air bubble radius and pressure distribution are derived based on the perturbation method for a small amplitude of sinusoidal motion, and the analytical results are compared with the numerical results. From the calculated results, the combined effects of air bubble and fluid film inertia on the squeeze film force are clarified
17 citations
TL;DR: In this paper, a squeeze-film damper, consisting of two circular plates, having only normal oscillatory relative motion is considered, and the liquid lubricant between the plates is assumed to contain a single central gas bubble.
Abstract: A squeeze-film damper, consisting of two circular plates, having only normal oscillatory relative motion is considered. The liquid lubricant between the plates is assumed to contain a single central gas bubble. The effect of the bubble on the damper performance is analyzed. Comparison is made with the performance of a pure liquid damper. Substantial deviations in peak dynamic pressures are predicted which explain discrepancies between experimental and theoretical results reported in the literature.
16 citations