Topic
Lubrication theory
About: Lubrication theory is a research topic. Over the lifetime, 1713 publications have been published within this topic receiving 50261 citations. The topic is also known as: Fluid bearing.
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TL;DR: In this article, the steady-state film pressures of hydrodynamic journal bearings were obtained by solving modified Reynolds equation based on the micropolar lubrication theory, with the help of the steady state film pressures, the steadystate performance characteristics in terms of load-carrying capacity, misalignment moment and friction parameter of a journal bearing were obtained at various values of eccentricity ratio.
74 citations
TL;DR: In this article, a model for the evolution of a thin liquid coating on a horizontal cylinder is presented, where the cylinder rotates about its axis, carrying liquid around its circumference.
Abstract: A model for the evolution of a thin liquid coating on a horizontal cylinder is presented. The cylinder rotates about its axis, carrying liquid around its circumference. For a viscous coating, this leads to formation of a relatively thick coating where the cylinder surface moves upward. The model is based on lubrication theory, as the coating is thin compared to the cylinder radius, and includes the effects of cylinder rotation, gravity, surface tension, and flow along the cylinder axis. A two-dimensional numerical scheme based on finite differences is produced, for investigation of the case when axial flow is neglected. This numerical scheme is validated in appropriate limiting cases. Coating cross sections are obtained over a range of cylinder rotation rates, for realistic parameter values. These show a transition from pendant drops hanging beneath the cylinder to a nearly uniform coating wrapped around it as rotation rate is increased.
73 citations
TL;DR: Collisions between millimeter-size bubbles in water against a glass plate are studied using high-speed video and accurate predictions of dimple formation and subsequent film drainage are obtained.
Abstract: Collisions between millimeter-size bubbles in water against a glass plate are studied using high-speed video. Bubble trajectory and shape are tracked simultaneously with laser interferometry between the glass and bubble surfaces that monitors spatial-temporal evolution of the trapped water film. Initial bubble bounces and the final attachment of the bubble to the surface have been quantified. While the global Reynolds number is large (� 10 2 ), the film Reynolds number remains small and permits analysis with lubrication theory with tangentially immobile boundary condition at the air-water interface. Accurate predictions of dimple formation and subsequent film drainage are obtained.
73 citations
TL;DR: In this article, a Faxen law for the pressure moment of one rigid particle in a general low-Reynolds number flow is found in terms of the ambient pressure, and the pressure moments of two rigid spheres immersed in a linear ambient flow are calculated using multipole expansions and lubrication theory.
Abstract: The pressure moment of a rigid particle is defined to be the trace of the first moment of the surface stress acting on the particle. A Faxen law for the pressure moment of one spherical particle in a general low‐Reynolds‐number flow is found in terms of the ambient pressure, and the pressure moments of two rigid spheres immersed in a linear ambient flow are calculated using multipole expansions and lubrication theory. The results are expressed in terms of resistance functions, following the practice established in other interaction studies. The osmotic pressure in a dilute colloidal suspension at small Peclet number is then calculated, to second order in particle volume fraction, using these resistance functions. In a second application of the pressure moment, the suspension or particle‐phase pressure, used in two‐phase flow modeling, is calculated using Stokesian dynamics and results for the suspension pressure for a sheared cubic lattice are reported.
73 citations
TL;DR: In this paper, the authors investigate the dynamics of thin films driven by gravity on the outer surface of a cylinder and a sphere, and show that the thickness of the flow remains uniform in space and decreases in time like t − 1/2 near the top of both the cylinder and the sphere.
Abstract: We investigate the dynamics of thin films driven by gravity on the outer surface of a cylinder and sphere. The surface is rigid, stationary and the axis of the cylinder is horizontal. An instantaneous release of a constant volume of fluid at the top of the cylinder or sphere results initially in a two-dimensional or axisymmetric current respectively. The resultant flow of a thin film of fluid is described using lubrication theory when gravity and viscous forces govern the dynamics. We show that the thickness of the flow remains uniform in space and decreases in time like t ―1/2 near the top of both the cylinder and the sphere. Analytic solutions for the extent of the flow agree well with our experiments until the advancing front splits into a series of rivulets. We discuss scalings of the flow at the onset of the instability as a function of the Bond number, which characterizes the relative importance of gravity and surface tension. The experiments, conducted within an intermediate range of Bond numbers, suggest that the advancing front becomes unstable after it has propagated a critical distance, which depends primarily and monotonically on the volume of fluid and not on the viscosity of fluid. Releasing a sufficiently large volume of fluid ensures that rivulets do not develop on either a cylinder or sphere.
73 citations