Network numerical analysis of hydromagnetic squeeze film flow dynamics between two parallel rotating disks with induced magnetic field effects

Considering the transient squeezing motion, the magneto-hydrodynamic (MHD) steady and dynamic characteristics of one-dimensional slider bearings lubricated with an electrically conducting fluid in the consideration of a transverse magnetic field are numerically investigated. Using the MHD motion equations and, the continuity equation, we have derived a MHD dynamic Reynolds-type equation, which is applicable to slider bearings taking into account the squeezing effect ∂ h/ ∂ t, in which the general film-shape function is described by h=h(x, t). A closed-form solution for the pressure of an inclined-plane slider is obtained and applied to predict the MHD dynamic stiffness and damping characteristics of bearings. According to the results obtained, the application of externally applied magnetic fields signifies an apparent increase in the MHD steady film pressure. Comparing with the classical non-conducting-lubricant case, the applied magnetic-field effects characterized by the Hartmann number provide ...

Dynamic stiffness and damping characteristics of one-dimensional magneto-hydrodynamic inclined-plane slider bearings:

This article presents predictive analysis of load-carrying capacity, tractive efficiency and response time of parallel annular discs intervened with a film of lubricant under combined shear and squeeze film motions. This configuration represents operational characteristics of viscous coupling systems. In particular, the case of viscous dampers for tractive torque generation and distribution in all-wheel-drive off road vehicles is studied. Various forms of lubricant behaviour, from idealised Newtonian to that of non-Newtonian silicone-based fluids and incompressible isothermal electrically conducting couple stress fluids, subjected to a magneto-hydrodynamic field are studied. The solution for the magneto-hydrodynamics includes combined solution of modified Reynolds equation and Stoke's micro-continuum for couple stress fluids in squeeze and shear with rotational fluid inertia, an approach not hitherto reported in the literature. It is shown that in general magneto-hydrodynamic couple stress fluids enhance the load-carrying capacity of the contact and inhibit the incidence of thin films, which can result in direct contact of surfaces. Rotational inertia decreases the load-carrying capacity, although in general the magneto-hydrodynamic fluids show better load-carrying capacity and tractive efficiency than the other alternatives. However, they exhibit a lower response time under the assumed isothermal condition. Nevertheless, the magneto-hydrodynamic fluids are best suited to applications in viscous coupling systems because of their controllability.

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Magneto-hydrodynamics of couple stress lubricants in combined squeeze and shear in parallel annular disc viscous coupling systems:

Analysis of couple stress fluid lubricated partially textured slip slider and journal bearing using narrow groove theory

Optimal film shape for two-dimensional slider bearings lubricated with couple stress fluids

The analysis of squeeze‐film performances between curved annular plates with an electrically conducting fluid in the presence of a transverse magnetic field is presented in this study. The magneto‐hydrodynamic (MHD) Reynolds‐type equation for squeezing‐film curved annular disks is derived using the continuity equation and the MHD motion equations. A closed‐form solution for the squeezing film pressure is obtained, and applied to predict the MHD squeeze‐film characteristics. According to the results obtained, the presence of applied magnetic fields signifies an increase in the MHD squeeze‐film pressure. Compared with the classical non‐conducting‐lubricant case, the magnetic‐field effect characterized by the Hartmann number provides an enhancement to the MHD load‐carrying capacity and the response time, especially for larger values of the curved shape parameter or smaller values of inner‐outer radius ratio of the curved annular disks.

Analysis of magneto‐hydrodynamic squeeze film characteristics between curved annular plates

Purpose – The purpose of the present study is to provide the dynamic characteristics of long journal bearings lubricated with couple stress fluids.Design/methodology/approach – Based upon the micro‐continuum theory generated by Stokes, the dynamic Reynolds‐type equation governing the film pressure is derived to account for the couple stress effects resulting from the non‐Newtonian behavior of complex fluids. By applying the linear stability theory to the non‐linear equations of motion the journal rotor, the equilibrium positions and dynamic characteristics of the system are evaluated.Findings – As compared to the classical Newtonian model, the effects of couple stresses signify enhanced stiffness and damping coefficients (including KXX, KXY , BXX and BXY) at moderate values of the steady eccentricity ratio. Totally, as the rotor center operates at an eccentricity ratio about es≤0.71, long bearings lubricated with couple stress fluids under small disturbance results in a higher stability threshold speed th...

Linear stability analysis of long journal bearings: couple stress fluid model

A theoretical study of the combined effects of non‐Newtonian couple stresses and fluid inertia forces on the squeeze‐film behaviors for parallel circular plates is presented in this paper. Based upon the micro‐continuum theory, the Stokes constitutive equations are used to account for the couple stress effects resulting from the lubricant blended with various additives. The convective inertia forces included in the momentum equation are approximated by the mean value averaged across the fluid film thickness. Numerical solutions for the squeezing film characteristics are presented for various values of couple stress parameter and Reynolds number. Comparing with the classical Newtonian non‐inertia flow, the combined effects of couple stresses and convective inertia forces result in a larger load‐carrying capacity and therefore, increase the response time of the squeezing film plates.

Effects of couple stresses and convective inertia forces in parallel circular squeeze‐film plates

Purpose – The purpose of this paper is to investigate the effects of non-Newtonian rheology on the dynamic characteristics of a secant-shaped couple-stress lubricated slider bearing. Design/methodology/approach – By applying the linear dynamic theory to the film force equation, a closed-form solution of the stiffness and damping coefficients is obtained for the secant-shaped bearing taking into account the non-Newtonian effects of Stokes couple stress fluids. Findings – Comparing with the secant-shaped Newtonian-lubricant bearing, the effects of non-Newtonian couple stresses provide an apparent improvement in the dynamic stiffness and damping characteristics, especially for the secant-shaped slider bearing operating at lower squeezing-film heights and with larger non-Newtonian couple stress parameters. Originality/value – Comparing with those of the inclined plane-shaped non-Newtonian slider bearings, better dynamic stiffness and damping performances are provided for the secant-shaped non-Newtonian slider...

The effects of non-Newtonian rheology in the dynamic coefficients of wide slider bearings with a secant-shaped film profile

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...

Rong‐Fang Lu

Papers

Analysis of magneto‐hydrodynamic squeeze film characteristics between curved annular plates

Linear stability analysis of long journal bearings: couple stress fluid model

Effects of couple stresses and convective inertia forces in parallel circular squeeze‐film plates

The effects of non-Newtonian rheology in the dynamic coefficients of wide slider bearings with a secant-shaped film profile

A closed-form solution in piezo-viscous squeeze films between a long cylinder and an infinite plate