Search results

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.

The purpose of the present study is to provide the dynamic characteristics of long journal bearings lubricated with couple stress fluids.

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.

As compared to the classical Newtonian model, the effects of couple stresses signify enhanced stiffness and damping coefficients (including K_XX, K_XY , B_XX and B_XY) at moderate values of the steady eccentricity ratio. Totally, as the rotor center operates at an eccentricity ratio about ε_s≤0.71, long bearings lubricated with couple stress fluids under small disturbance results in a higher stability threshold speed than that of the Newtonian‐lubricant case.

These findings provide engineers useful information in designing journal‐bearing systems.

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.