Mechanics of a Porous Web Moving Over a Cylindrical Guide

Abstract

A model for analyzing the interfacial conditions of a porous web moving over a cylindrical rigid guide is presented. This problem is different from the classical foil bearing problem due to the fact that the air can diffuse through the porous web itself. A micromechanics model is used to express the web porosity as a function of the fiber volume fraction of the web. Darcy’s law is used to account for the air flow and pressure drop across the web thickness, and a new modified Reynolds equation is derived to model the airflow in the web-guide interface. The porous web is modeled as a moving cylindrically curved beam, and the solid-body contact between the web and the guide is modeled using an asperity compliance function. The governing equations are nondimensionalized and important nondimensional parameters are identified. The coupled nonlinear steady-state system is solved using a modified Newton-Raphson algorithm. The traction characteristics of the web are presented for different porosity levels, asperity height, and compliance. [S0742-4787(99)00102-8]