Prediction of lateral vibration characteristics of a full-size rotor-bearing system by using those of its scale models

The object of this paper is to study how to predict the lateral vibration characteristics of the full-size rotor-bearing system by using the scale rotor-bearing model and the associated scaling laws, such that one may significantly reduce the time and money required by the experiments. To this end, the scaling laws for all the relevant parameters regarding the full-size rotor-bearing system and its scale model (such as, sizes of the constituent members, spring constants and damping coefficients of the supports, natural frequencies (of free vibration) and forced vibration displacements, etc.) are derived first from the equations of motion of the last two systems. Next, the scaling factors for all relevant parameters of the above-mentioned two systems are determined with the theory of dimensional analysis. Now, based on all of the above-mentioned relevant parameters of the full-size rotor-bearing system, one may determine the corresponding parameters of the scale rotor-bearing model by using the associated scaling factors and predict the vibration characteristics of the full-size rotor-bearing system by using the corresponding ones of the scale rotor-bearing model. Finally, the influence of constituent-member sizes on the similarity of natural frequencies (of free vibrations) and the influence of spring constants, damping coefficients and external loads on the similarity of dynamic responses (of forced vibrations) are investigated. Because the literature concerning the use of scaling laws and scale rotor-bearing model for predicting free and forced vibration characteristics of full-size rotor-bearing system is rare, this paper provides a complete and systematic theory and technique in this aspect.