Experimental analysis of rod bundle hydrodynamics

LAZO, PABLO; MARCEL CHRISTIAN PABLO; NALÍN, OSCAR

Bahia Blanca

Workshop; XVIII Workshop on Information Processing and Control  RPIC 2019; 2019

Investigating the flow behavior inside fuel elements bundles (FB) is of crucial importance to quantify their cooling capabilities and also the thermal limit. For that reason it has been an active research topic since several decades.In this work we present experimental results aimed to study the complex flow behavior in a geometry resembling FB. We make use of a non-intrusive instrumentation able to capture detailed pressure measurements in the surface of the FB. By analyzing the power spectrum density (PSD) of the fluctuating pressure signals it is possible to quantify the power spectra of the kinematic intensity of the turbulent flow in a wide spatial range, including regions inside the spacer grids. In this manner we show the characteristics of the vortex originated by the spacer grid and their spatial evolution. Measurements also allow observing the characteristics of the so-called Large Scale Coherent Vortex (LSCV). Moreover, the data analysis allows studying the correlation between different pressure signals and the LSCV interactions making use of the cross-correlation signal analysis. The application of the Short Time PSD (STPSD) together with the Wavelet Transform decomposition (WT) and the Recurrence Quantification Analysis (RQA) to the signal allowed identifying a pulsating behavior in the pressure fluctuations.The results of this work are important to nuclear designers since they can help understanding turbulent mixing and to calculate mixing coefficients. By identifying regains with deficient cooling it is possible to optimize the FB design.