Application of dynamical system scaling method on simple gravity-driven draining process

Abstract

ABSTRACT Scaling analysis is widely used in the design of nuclear reactor passive safety systems to ensure that the scale-down test facilities can accurately capture the important phenomena in the prototypic system. In this study, the scaling distortion of a gravity-driven draining system has been analyzed with Hierarchical Two-Tiered Scaling (H2TS) method, based on the initial static characteristic values. In the draining process, however, the key parameters may vary with respect to time, leading to a certain level of scaling distortion. To evaluate the time-dependent scaling distortion, a Dynamical System Scaling (DSS) method is applied. Through comparisons of scaling results of the two scaling methods, it is concluded that the H2TS method can effectively scale the gravity-driven draining process in different geometric sizes, if the variations in the friction factor is negligible. As the draining process slows down, accompanied by an increase in the friction factor, the distortions in water level and in discharge velocity become significant, especially at the end of the draining process in a model of relatively small geometry size. This preliminary study demonstrated the process of scaling distortion analysis using the DSS identity method, and could shed light to the scaling distortion evaluation of testing programs.