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Journal bearings are applied in internal combustion engines due to their favourable wearing quality and operating characteristics. Under certain operating conditions damage of the journal bearing can occur caused by cavitation. The cavitation reduces the load capacity and leads to material erosion. Experimental investigations of cavitating flows in dimension of real journal bearing are difficult to realize or almost impossible caused by the small gap and transient flow conditions. Therefore numerical simulation is a very helpful engineering tool to research the cavitation behaviour. The CFD-Code OpenFOAM is used to analyse the flow field inside the bearing. The numerical cavitation model based on a bubble dynamic approach and requires necessary initial parameter for the calculation, such as nuclei bubble diameter, the number of nuclei and two empirical constants. The first part of this paper shows the influence of these parameters on the solution. For the adjustment of the parameters an experiment of Jakobsson et.al. [1] was used to validate the numerical flow model. The parameters have been varied according to the method Design of Experiments (DoE). With a defined model equation the parameters determined, to identify the parameter for CFD-calculations in comparison to the experimental values. The second part of the paper presents investigations on different geometrical changes in the bearing geometry. The effect of these geometrical changes on cavitation was compared with experimental results from Wollfarth [2] and Garner et.al. [3].

In many previous studies the main focus was put on the pressure distribution in the lubricating gap. Due to the limited space in the gap an investigation of the velocity distribution is very difficult or rather impossible. Based on the geometrical shapes of a real journal bearing, a bearing model test rig with an increased relative gap width has been developed. Thus, it is possible to detect the distribution of the flow speed within the gap by using a Laser Doppler Velocimeter (LDV). The comparability of the flow to the flow in a real journal bearing is ensured by observing the Reynolds similarity. Due to a targeted eccentricity in the system and the circumferential groove over 180°, there is in connection with the outlet hole in the rotating shaft a permanent change in the outflow conditions. The consequence is a periodically varying system pressure with effects to the pressure and volumetric flow rate at the inlet and outlet. The velocity measurements with a triggered LDV are done by considering these transient boundary conditions at the system boundaries. In this paper the experimental setup, the expiration of the investigations and some exemplary results are presented. Attendant to the experiment, numerical simulations are carried out and the results are compared with the experimental data.