New concepts in numerical prediction of cavitation in bearings

An analogy between the mathematical modeling of transonic flow and cavitation in bearings is developed. The similarities between these two entirely different physical phenomena can be exploited to the benefit of both fields. In this thesis, a few recent computation procedures used in transonic flow analyses are extended, suitably modified and implemented in the numerical prediction of cavitation in bearings.; The cavitation algorithm developed by Elrod, to automatically predict film rupture and reformation boundaries, is modified by introducing a type differencing technique in the shear flow term to automatically change the form of finite differencing (central or upwinded) between the full film and cavitated regions. This portion of the original Elrod algorithm was developed by numerical trial and error and hence, this modification makes the algorithm non-empirical and provides a suitable base for further improvement. Several one and two dimensional bearings are analysed using the modified algorithm and the results favorably compare with the predictions using the Elrod algorithm and experimental data.; To handle geometrically complicated problems, grid generation/transformation and grid adaptation techniques are added to the modified cavitation algorithm. Grid generation is done using body fitted coordinate system. Using these techniques, the grid is dynamically restructured as the solution progresses to provide more accurate results with fewer grid points and a smaller amount of computer time. Performance of four journal bearing cases are analyzed and compared with the predictions using conventional orthogonal grid arrangements.; An approximate factorization (AF) technique is incorporated into the modified cavitation algorithm as the numerical solution procedure. This procedure is robust, efficient and quickly convergent. In the unsteady analysis of a bearing, to improve the accuracy of the transient solutions, a Newton iteration scheme is developed. These techniques are developed for both orthogonal and non-orthogonal grid arrangements.; Utilizing these improvements, the performance characteristics of line grooved and finite grooved journal bearings with misalignment varying in magnitude and direction are determined considering cavitation and starvation effects. The predicted performance parameters using the modified cavitation algorithm are also compared with the available experimental data.; Extension of transonic flow computational concepts in the algorithm, control over the grid arrangement and the numerical solution procedure have proved to be successful. It is expected that many more such extensions are possible and with them the numerical modeling of lubrication problems can be improved.