Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the rotor is flexible. The accuracy of prediction of the model at hand depends on its comprehensiveness. In this study, we construct three bearing models of increasing modeling comprehensiveness and use these to predict the response of two different rotor-bearing systems. The main goal is to evaluate the correlation with measurement data as a function of modeling comprehensiveness: 1D versus 2D pressure prediction, distributed versus lumped thermal model, Newtonian versus non-Newtonian fluid description and non-mass-conservative versus mass-conservative cavitation description. We conclude that all three models predict the existence of critical speeds and whirl for both rotor-bearing systems. However, the two more comprehensive models in general show better correlation with measurement data in terms of frequency and amplitude. Furthermore, we conclude that a thermal network model comprising temperature predictions of the bearing surroundings is essential to obtain accurate predictions. The results of this study aid in developing accurate and computationally-efficient models of flexible rotors supported by plain journal bearings. ... Read more

An efficient symmetric Lanczos method for the solution of vibro-acoustic eigenvalue problems is presented in this paper. Although finite element discretization results in real but nonsymmetric system matrices, we show that an efficient iteration scheme on a symmetric representation can be built up by using a transformation matrix. In order to decrease the numerical costs of the orthogonalizations performed, we propose to use a partial orthogonalization scheme for the symmetric case. The proposed method is tested on two large problems in order to demonstrate its efficiency and accuracy. ... Read more

Prior to any structural system realization during the design phase, the structural dynamic should be characterized. Dynamic characterization provides the designers with local and global dynamic information which can be used to optimize the structures. To characterize the dynamic of too large and complex structures generally Dynamic Substructuring (DS) techniques are used. Experimental DS is one of these techniques and is recently more in use. Many researchers put effort in developing and evolving new concepts. The substructuring focus group at Society for Experimental Mechanics (SEM) uses a small-scale wind turbine, Ampair 600, in a combined effort to validate, classify and advance these techniques. In this paper the substructuring results, obtained with the LM FBS formulation applied to the wind turbines rotor are given. The Interface Deformation Mode (IDM) method is adopted and applied to overcome the lack of Rotational Degrees of Freedom (RDoF) and to minimize the measurement noise. To include the joint stiffness and damping a Substitute (Fixture) is used and two methods are proposed to model flexible and rigid Cyclic Symmetric Structures (CSS). The results obtained in this first substructure analysis of the rotor show that good results can be found in the lower frequency range. ... Read more