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Jaw Ren Lin - One of the best experts on this subject based on the ideXlab platform.

  • effects of fluid inertia forces in ferrofluid lubricated circular stepped Squeeze Films shliomis model
    Industrial Lubrication and Tribology, 2016
    Co-Authors: Jaw Ren Lin, Tzuchen Hung
    Abstract:

    Purpose This paper aims to study the inertia Squeeze film characteristics between ferrofluid-lubricated circular stepped disks. Owing to the development of modern machine systems, the application of ferrofluids has received great attention. Because the circular disks are a special situation of circular stepped Squeeze Films, a further study of fluid inertia force effects on the ferrofluid-lubricated circular stepped squeezing mechanism is motivated. Design/methodology/approach On the basis of the ferrohydrodynamic flow model of Shliomis incorporating the momentum integral method, the effects of fluid inertia forces in ferrofluid-lubricated circular stepped Squeeze Films in the presence of external magnetic fields are investigated in this study. Analytical solutions of Squeeze film performances are derived. Findings The fluid inertia force effects provide an increased load capacity and a longer Squeeze film time for the ferrofluid-lubricated circular stepped Squeeze film, especially for a larger value of the inertia parameter, the Langevin parameter and the volume concentration and a smaller value of the radius ratio and the step height ratio. Originality/value For engineering applications, numerical tables for Squeeze film loads of circular stepped disks are also provided in this paper.

  • Fluid inertia force effects in hydromagnetic sphere-plate Squeeze Films
    Tribology International, 2015
    Co-Authors: Jaw Ren Lin
    Abstract:

    This paper investigates the influences of fluid inertia forces in hydromagnetic sphere-plate Squeeze Films. Applying the averaged inertia principle, a megnetohydrodynamic pressure gradient equation has been derived. From the results obtained, the combined effects of fluid inertia forces and electrical conducting fluids in the presence of external magnetic fields provide better Squeeze film characteristics, and lengthen the operating life of the sphere-plate system as compared to the non-inertia non-conducting-fluid case.

  • magneto hydrodynamic non newtonian curved circular Squeeze Films
    Journal of Marine Science and Technology, 2014
    Co-Authors: Jaw Ren Lin, Li-ming Chu, Chiren Hung
    Abstract:

    The Squeeze film performances between curved circular plates lubricated with an electrically conducting non-Newtonian fluid in the presence of external magnetic fields are investigated in this paper. Based upon the magneto-hydrodynamic flow theory together with the Stokes microcontinuum theory, the magneto-hydrodynamic non-Newtonian Reynolds equation is derived and applied to predict the curved circular Squeeze film behaviors. Comparing with the hydrodynamic Newtonian case, the Squeeze film characteristics for curved circular plates are improved by the use of an electrically conducting non-Newtonian fluid in the presence of external magnetic fields. Numerical values of the load capacity and the approaching time are provided in Tables for engineering applications.

  • a closed form solution in piezo viscous Squeeze Films between a long cylinder and an infinite plate
    Industrial Lubrication and Tribology, 2014
    Co-Authors: Jaw Ren Lin
    Abstract:

    Purpose – The aim of this study is to extend the squeezing film problems between a long cylinder and an infinite plate, considering the piezo-viscous behavior (PVB) of the Barus experimental relationship. Design/methodology/approach – By integrating the nonlinear Reynolds-type differential equation directly, an analytical film-pressure solution is obtained and applied to investigate the load-carrying capacity and the approaching time. Findings – Compared with the case of constant-viscosity lubricants (CVLs), the effects of PVB are found to provide higher load-carrying capacities and longer approaching times for the squeezing Films. Originality/value – It is found that when the cylinder is Squeezed to a dimensionless central film height of 0.3, the dimensionless approaching time required for the CVL case is 4.922. However, the effects of PVB (α 0.0001, 0.001, 0.005 and 0.01) provide longer approaching times with values of 8.324, 8.438, 9.028 and 10.079. The cylinder-plate Squeeze film system considering th...

  • inertia force effects in the non newtonian couple stress Squeeze film between a sphere and a flat plate
    Tribology International, 2013
    Co-Authors: Jaw Ren Lin
    Abstract:

    Abstract On the basis of the Stokes micro-continuum theory together with the method of mean averaged inertia, the influences of fluid inertia forces on the non-Newtonian Squeeze film characteristics between a sphere and a flat plate have been presented. Comparing with the case of a non-inertia non-Newtonian lubricant, the consideration of fluid inertia forces provides a longer Squeeze film time especially for the Squeeze film operating with a lower film height, and a larger non-Newtonian parameter and density parameter. It prolongs the life of Squeeze Films.

Robert J Rogers - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear fluid forces in cylindrical Squeeze Films part i short and long lengths
    Journal of Fluids and Structures, 2001
    Co-Authors: Y Han, Robert J Rogers
    Abstract:

    Using three approximation methods, nonlinear models have been derived for short and long cylindrical Squeeze Films with arbitrary inner cylinder motions. Elliptical and parabolic velocity profiles are employed in the derivation in order to determine the effects of the choice of velocity profile. The only differences in the final Squeeze film equations, due to the three approximation methods and the two velocity profiles, are in the four constant coefficients. Each term in the Squeeze film equations is a nonlinear function of cylinder position. Comparing the present nonlinear expressions with existing models for short cylindrical Squeeze Films shows that the force terms are either exactly the same or have the same trends with instantaneous eccentricity values. For long cylindrical Squeeze Films, the present expressions have some force terms which are essentially the same as in other studies, while other force terms show variations with position which are very different from a previously published study.

  • nonlinear fluid forces in cylindrical Squeeze Films part ii finite length
    Journal of Fluids and Structures, 2001
    Co-Authors: Y Han, Robert J Rogers
    Abstract:

    Abstract Two nonlinear models of finite-length cylindrical Squeeze Films are developed. The first finite-length model is formed using length-correction factors on a short cylindrical model, while the second finite-length model is constructed using side-leakage factors with an infinitely long model. Each model has seven force terms which are nonlinear functions of instantaneous cylinder position. The two models are evaluated through experimental measurements using two geometrical configurations where 50·6 mm and 25 mm diameter cylinders undergo 160 cases of radial and offset-linear motions. Comparing the theoretical predictions of Squeeze force waveforms with measurements, and also with previous models by Lu & Rogers, shows that the present finite-length models are quite reasonable. By investigating each force term, the present models are modified slightly and better predictions are obtained for most test cases. Without empirical corrections, the models tend to underestimate the unsteady inertia terms and are unable to predict the frequency dependence of the viscous terms.

  • a nonlinear model for short length cylindrical Squeeze Films with large planar motions
    Journal of Tribology-transactions of The Asme, 1992
    Co-Authors: Robert J Rogers
    Abstract:

    A rotating shaft vibrating in a Squeeze film bearing and a tube in a heat exchanger oscillating with fluid-filled cylindrical supports both involve cylindrical Squeeze Films. Many theoretical and experimental results show that the Squeeze film force consists of both a damping force and an inertia force. For relatively large amplitude motions or when the initial eccentricity is large, the time waveform of the Squeeze force is significantly nonlinear. In order to predict the transient response of a rotor with Squeeze film bearings or a heat exchanger tube subject to flow induced vibration, the nonlinear instantaneous Squeeze force must be calculated. This paper presents a model for the instantaneous cylindrical Squeeze film force for planar motion. The Squeeze film model for a two-dimensional plate shows that there are three nonlinear terms included in the Squeeze force. Based on this model, an equation for the short length, cylindrical Squeeze film force for moderately large eccentricities is developed. The equation includes the three nonlinear terms: the viscous term, the unsteady inertia term, and the convective inertia term. All three terms are functions of instantaneous eccentricity. The equation predicts the nonlinear multi-harmonic and unsymmetrical time waveforms of the instantaneous Squeeze film force for planar motions with both in-line and out-of-line initial eccentricities. The results are compared with experimentally measured Squeeze force waveforms obtained with a length to diameter ratio of 0.75 and instantaneous eccentricities less than 0.75. The Squeeze force waveforms for this finite length geometry can be reasonably predicted if correction coefficients, which account for the circumferential flow, are applied to the three nonlinear force terms. These coefficients are themselves functions of frequency, initial eccentricity and amplitude.

  • estimation of linearized force coefficients for cylindrical Squeeze Films
    Tribology Transactions, 1991
    Co-Authors: Robert J Rogers
    Abstract:

    Linearized damping and inertial coefficients for cylindrical Squeeze Films with centered and off-centered elliptical motions have been determined, experimentally through a generalized least squares estimation technique. The estimation quality is evaluated using statistical analysis, and the existence of damping coupling coefficients and, inertial coupling coefficients is discussed. The effects of initial eccentricity, oscillation frequency and oscillation amplitude on the force coefficients are examined. New dependencies of the coefficients on oscillation frequency and amplitude are shown. This paper presents semi-empirical formulas with corresponding confidence intervals for the damping and inertial coefficients based on the estimation, results and analytical predictions. A comparison with theoretical predictions is made and favorable agreement is found. These results are of value for the prediction of the dynamic response of heal exchanger lubes, as well as Squeeze film dampers in turbomachinery.

Y Han - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear fluid forces in cylindrical Squeeze Films part i short and long lengths
    Journal of Fluids and Structures, 2001
    Co-Authors: Y Han, Robert J Rogers
    Abstract:

    Using three approximation methods, nonlinear models have been derived for short and long cylindrical Squeeze Films with arbitrary inner cylinder motions. Elliptical and parabolic velocity profiles are employed in the derivation in order to determine the effects of the choice of velocity profile. The only differences in the final Squeeze film equations, due to the three approximation methods and the two velocity profiles, are in the four constant coefficients. Each term in the Squeeze film equations is a nonlinear function of cylinder position. Comparing the present nonlinear expressions with existing models for short cylindrical Squeeze Films shows that the force terms are either exactly the same or have the same trends with instantaneous eccentricity values. For long cylindrical Squeeze Films, the present expressions have some force terms which are essentially the same as in other studies, while other force terms show variations with position which are very different from a previously published study.

  • nonlinear fluid forces in cylindrical Squeeze Films part ii finite length
    Journal of Fluids and Structures, 2001
    Co-Authors: Y Han, Robert J Rogers
    Abstract:

    Abstract Two nonlinear models of finite-length cylindrical Squeeze Films are developed. The first finite-length model is formed using length-correction factors on a short cylindrical model, while the second finite-length model is constructed using side-leakage factors with an infinitely long model. Each model has seven force terms which are nonlinear functions of instantaneous cylinder position. The two models are evaluated through experimental measurements using two geometrical configurations where 50·6 mm and 25 mm diameter cylinders undergo 160 cases of radial and offset-linear motions. Comparing the theoretical predictions of Squeeze force waveforms with measurements, and also with previous models by Lu & Rogers, shows that the present finite-length models are quite reasonable. By investigating each force term, the present models are modified slightly and better predictions are obtained for most test cases. Without empirical corrections, the models tend to underestimate the unsteady inertia terms and are unable to predict the frequency dependence of the viscous terms.

N B Naduvinamani - One of the best experts on this subject based on the ideXlab platform.

  • effect of roughness on hydromagnetic Squeeze Films between porous rectangular plates
    Tribology International, 2010
    Co-Authors: N B Naduvinamani, Syeda Thasneem Fathima, Salma Jamal
    Abstract:

    The theoretical investigations made in this paper are to study the combined effects of unidirectional surface roughness and magnetic effect on the performance characteristics of a porous Squeeze film lubrication between two rectangular plates. The stochastic Reynolds equation accounting for the magnetic effect and randomized surface roughness structure is mathematically derived. The expressions for dimensionless pressure, load carrying capacity and Squeeze film time are obtained. Results are computed numerically and it is observed that a roughness effect enhances pressure, load carrying capacity and Squeeze film time.

  • surface roughness effects on Squeeze Films in curved circular plates
    Industrial Lubrication and Tribology, 2004
    Co-Authors: N B Naduvinamani, G Gurubasavaraj
    Abstract:

    The stochastic theory of hydrodynamic lubrication of rough surfaces is used to study the effect of surface roughness on the performance of the Squeeze film between circular curved plate and a flat plate. In the context of stochastic theory, two types of one‐dimensional roughness patterns (circumferential and radial roughness) are considered. The stochastic Reynolds equation for the two types of roughness patterns is derived. The closed form expressions for the mean Squeeze film pressure, mean load carrying capacity and the Squeeze film time are obtained. It is found that, the circumferential one‐dimensional surface roughness pattern increases the mean Squeeze film pressure and the load carrying capacity whereas the radial one‐dimensional roughness pattern affects the Squeeze film characteristics.

  • couple stress Squeeze Films between porous rectangular plates
    Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2003
    Co-Authors: N B Naduvinamani, Syeda Tasneem Fathima, P S Hiremath
    Abstract:

    AbstractIn this paper, the Squeeze-film lubrication theory between two isotropic porous rectangular plates has been advanced to analyse the effects of couple stresses arising due to the presence of microstructure additives in the lubricant, using the Stokes theory of couple-stress fluids. The most general form of the modified Reynolds equation is derived for the Squeeze-film lubrication of the porous rectangular plates by taking into account of the velocity slip at the porous interface. An eigentype of expression is obtained for the Squeeze-film pressure. The effects of the isotropic permeability, the couple stresses and the velocity slip parameters on the characteristics of the Squeeze-film lubrication are discussed. A significant increase in the load-carrying capacity and the delayed Squeeze-film time are observed for the couple-stress fluids in comparison with Newtonian fluids.

  • Squeeze film lubrication of a short porous journal bearing with couple stress fluids
    Tribology International, 2001
    Co-Authors: N B Naduvinamani, P S Hiremath, G Gurubasavaraj
    Abstract:

    This paper presents the theoretical investigations of the rheological effects of the couple stress fluids on the static and dynamic behaviour of the pure Squeeze Films in the porous journal bearings. The present study predicts the effects of percolation of the polar additives (microstructures) into the porous matrix on the performance of Squeeze Films in the porous journal bearings. The most general modified Reynolds-type equation is derived for a porous journal bearing with no journal rotation. The analysis takes into account of the tangential velocity slip at the porous interface by using the BJ-slip condition. The cases of a short porous journal bearing under a constant applied load and that under an alternating load are analyzed. As compared to the Newtonian lubricants, the lubricants which sustain the couple stresses yield an increase in the load carrying capacity. Under a cyclic load the couple stress fluids provide a reduction in the journal velocity and an increase in the minimum permissible height of Squeeze Films.

R M Patel - One of the best experts on this subject based on the ideXlab platform.

  • Hydromagnetic Squeeze Films between Two Conducting Rough Porous Elliptical Plates
    2015
    Co-Authors: P A Vadher, G M Deheri, R M Patel
    Abstract:

    The present study analyzed the performance of hydromagnetic Squeeze Films between 2 conducting rough porous elliptical plates. The bearing surfaces were assumed to be transversely rough. The roughness of the bearing surfaces was characterized by a stochastic random variable with non-zero mean, variance, and skew-ness. The associated Reynolds equation was stochastically averaged with respect to the random roughness parameter. This equation was then solved with appropriate boundary conditions to obtain the bearing performance characteristics, such as load carrying capacity and response time. The results are presented graphically. It was observed that the transverse surface roughness adversely affected the bearing system and that the bearing suffered due to transverse surface roughness. The results show that hydromagnetic lubrication significantly increased the load carrying capacity. With this type of bearing system porosity effects were almost negligible, up to a certain porosity. Additionally, the load carrying capacity increased due to the negatively skewed roughness and conductivity of the plates. Furthermore, the negative effect induced by the porosity, standard deviation, and variance (+ve) were compensated for, to a considerable extent, by the combined effect of conductivity and magnetization in the case of negatively skewed roughness. Results of the present study suggest that roughness must be given due consideration while designing such bearing systems

  • Performance of hydromagnetic Squeeze Films between conducting porous rough conical plates
    Meccanica, 2010
    Co-Authors: P A Vadher, G M Deheri, R M Patel
    Abstract:

    An endeavor has been made to discuss the behavior of hydromagnetic Squeeze film between two conducting rough porous conical plates. The plates are considered to be electrically conducting and the clearance space between them is filled by an electrically conducting lubricant. A transverse magnetic field is applied between the plates. Efforts have been made to solve the concerned Reynolds’ equation with the associated boundary conditions to get the pressure distribution. This in turn, is used to obtain the expression for load carrying capacity leading to the calculation of the response time. The results are presented graphically as well as in tabular form. It is suggested by the results that the bearing system records an enhanced performance as compared to that of a bearing system working with a conventional lubricant. It is noticed that the pressure, load carrying capacity and the response time increase steadily with increasing values of the magnetization parameter. In general, the bearing suffers owing to transverse surface roughness. However, the negatively skewed roughness tends to better the performance of the bearing system marginally. This performance gets further improved especially, when the negative variance is involved. It is observed that the semi-vertical angle increases the load carrying capacity. Besides, the conductivity also increases the load carrying capacity significantly. In addition, it is revealed that the negative effect induced by the porosity can be neutralized to a nominal extent by the positive effect of the magnetization parameter in the case of negatively skewed roughness in the presence of negative variance. Thus, this study provides ample scopes for improving the performance of the bearing system considerably by choosing a suitable combination of magnetization parameter, semi-vertical angle and the conductivities of the plates.

  • behaviour of hydromagnetic Squeeze Films between two conducting rough porous circular plates
    Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2008
    Co-Authors: P A Vadher, P C Vinodkumar, G M Deheri, R M Patel
    Abstract:

    In this paper, the problem of Squeeze Films between electrically conducting rough porous surfaces and electrically conducting lubricant in the presence of transverse magnetic field is investigated for circular shape of the bearing surfaces. The bearing surfaces are assumed to be transversely rough. The roughness of the bearing surface is modelled by a stochastic random variable with non-zero mean, variance, and skewness. The associated Reynolds equation is stochastically averaged with respect to the random roughness parameter. Then, it is solved with appropriate boundary conditions to get the pressure distribution, which is further used to obtain the load carrying capacity leading to the calculation of response time. The results are presented graphically. It is noticed that the bearing suffers on account of transverse surface roughness in general. However, the situation can be retrieved up to a certain extent in the case of negatively skewed roughness especially, when negative variance occurs by suitable ...