FLUID STRUCTURE INTERACTION IN JOURNAL BEARING DYNAMIC ANALYSIS BY FINITE ELEMENT

摘要

Typically, in numerical fluid flow computation the mesh is fixed in space for all time, but for problems which have moving boundaries, such as journal bearings, it is not suitable. Recent advances in finite element numerical control allow the conservation laws of the physical domain to be transformed into the computational domain. This permits large-scale motion of the computational boundary. The advantage of the resulting numerical model, over an empirical model, is the capability to observe the effect of changes in the geometry, material properties, and boundary conditions on bearing performance, for relatively low cost. The qualitative results of pressure and velocity distribution from the finite element analysis agreed well with the empirical and theoretical values. The quantitative results, however, were not in agreement. This is due to the inability of the current application of the finite element method to model cavitation. However, since the general qualitative effects are computed, the quantitative value should be in agreement with the physical journal bearing if elements which allow cavitation effects are incorporated or if the model is tuned to empirical data. For this application of the finite element method, 1/1000 of the journal axial length is modeled with boundary conditions representing infinite length. For analysis of practical journal bearings which model cross flow, Taylor vortices, etc., the number of elements must be increased by a factor of 1000. This would lead to models of between 2.5 to 5.0 million elements