MBS/FEM Co‐Simulation Approach for Lubrication Problems

Department of Mechanical Engineering, Multibody Systems,University of Kassel, D-34019 Kassel, GermanyHydrodynamic bearings are used in many technical systems, e.g., in combustion engines, in gear boxes or in rotor systems.To model such bearings, different methods are available. Often, reduced bearing models are applied which can be incor-porated into the multibody systems by analytical formulas or pre-computed look-up tables [1]. Such approaches are verytime-efficient but suffer from limited physical correctness. In order to improve the physical bearing model, the fluid flowand temperature field in the bearing gap have to be computed with partial differential equations which have to be solvedsimultaneously with the multibody system. These equations are nonlinear and have to be discretized with finite elements, forinstance. In the current work, we consider a fully coupled simulation of a multibody rotor system with a finite element modelfor the hydrodynamic bearings. A co-simulation interface between two commercial simulation tools is presented. For thesynchronization of the solvers, three numerical coupling approaches (an explicit, an implicit and a semi-implicit approach)are analyzed and compared. For the examined rotor/bearing system, it is shown that semi-implicit coupling techniques mayremarkably stabilize the solver coupling compared to well-established explicit co-simulation techniques [2]. Furthermore, areduction method is introduced and applied in connection with the semi-implicit coupling approach which can significantlydecrease the computation time compared with the classical full-implicit coupling approach [3].