Enhanced fluid bearing simulation with standard multi body systems

Fluid bearings are still fundamental elements of current machine design. Influenced by the growing requirements in terms of life cycle of all machine components the calculation methods have to be improved. In the past numerous simulation tools for bearings have been developed, which were mostly stand alone programs which are written in a specific program language and based on a quasistatic formulation. The basic equation describing the fluid film in a journal bearing is the REYNOLDS equation. This is a partial differential equation, which is derived from a particular case of the more general NAVIER-STOKES equations. The solution of this equation is the pressure distribution in the fluid filled gab. Until today there exists no closed analytical solution for this equation. Therefore many forms of approximations were developed to calculate the pressure distribution and the bearing force respectively. 2 Fluid bearings in MBS environment The implementation of the hydrodynamic forces is realised through a user defined force element, which is mostly written as FORTRAN subroutine. The first part of the subroutine determines the kinematical quantities in the journal bearing. The main part calls the hydrodynamic module, which solves the REYNOLDS equation and the last part calculates the nodal forces on each elastic marker due to the calculated pressure distribution. The prime reason to solve the REYNOLDS equation