Study of Hydrodynamic Lubication Mechanism based on the Theory of Turbulence

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First of all, turbulent plane Couette flow has been experimentally investigated to consider the structure of turbulent lubrication in an unloaded journal bearing. Mean velocity and turbulence have been measured in essentially fully developed flow from laminar to turbulent region. Mean velocity profiles are compared with theoretical profiles and the results of direct numerical simulation in the transition region. In the fully developed turbulent region, the velocity follows the logarithmic velocity profile U^+=2.5lny^++ 5.1 obtained by telbany and Reynolds in the wall region but outside the buffer layer layer, and the velocitybany and the velocity-defect law (U_c-U)/u*=R_f(1-y/h) in the core region, where U_c, u* and h are centerline vrlocity, friction velocity and half channel depth, respectively. Skin friction coefficient, turbulence intensity, Reynolds shear-stress and energy-density spectra are also discussed in comparison with the other results obtained previously.Subsequently, the … More structure of turbulent flow in the lubrication for the eccentricity ratio m=0.3 in a loaded journal bearing has been experimentally investigated in the two-dimensional channel between a sinusoidally waved wall and a plane noving belt. The flow is accelerated and decelerated in the main flow direction with the pressure gradient alternating in sign,so that the turbulence is in disequilibrium and greatly influenced by the inertia effect of the flow. The velocity profiles in the wall region are displaced above the logarithmic velocity profile of the turbulent Ciuette flow, depending on y^+ and x/1 (x=coordinate in the direction of main flow ; 1=one wavelength of sinusoidally waved wall). The value of U^+ in the wall region can be given by the function of both Van Driest damping constant A^+ and Karman constant k, which depend on a perssure gradient parameter <nu>dp/dx/(<rho>u*^3) and an inertia effect parameter. Half-power law and velocity defect law were also found in the gradient layer and the core region, respectively. Distribution of Reynolds shera-stress is much influenced by the inertia effect of normal velocity component caused by the secondary flow. Turbulence in tensities,ROO<<U'^2>> and √<V'^2>, were also measured and discussed. Less