Development of a simple substitute model to describe the normal force of fluids in narrow gaps

Abstract

Fluids in narrow gaps are employed frequently in many applications. The motivation for their use is diverse and ranges from hydrodynamic lubrication in plain bearings to the transport of hard particles into the working gap for the purpose of machining workpiece surfaces in lapping processes. Depending on the focus of the analysis, it may be useful to investigate the entire pressure field or to calculate only individual quantities. For example, in sophisticated simulations it may be of interest to know the resulting force of a fluid as a function of the external system state in order to describe its damping characteristics. Especially for the simulation of flows in narrow gaps, the Reynolds equation is a convenient choice, which, in contrast to the more general Navier‐Stokes equations, can lead to considerable savings in computational time because no three‐dimensional discretization is required, but only a two‐dimensional discretization. However, if not a highly detailed pressure field is of interest, but only simple relations such as the resulting force as a function of distance and velocity, and if this relation to be evaluated many times for different parameter combinations over a wide range of values, the use of a robust substitute model is a good choice. This article deals with the creation of such a substitute model based on the Reynolds equation taking cavitation into account.

Simplified description of hard particles in tribological systems using statistical sample particles

“…When exposed to static loads, SSPs show the same force-gap height behavior as a corresponding set of SPs in the gap. For this reason, SSPs can also be used in combination with SPs or in combination with the previously published gap heightsensitive fluid force model [15]. Dynamics simulations show an increasing underestimation of the variance of dynamic quantities such as the occurring normal force between the first two bodies due to a reduced variance in vertical motion with increasing sample size.…”