Modulation of flow meandering in a gap of a model of a peripheral subchannel of the fuel rod assembly
M.V. Shestakov, M.V. Tokarev
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: Experiment, turbulent flow, channels of complex shape, PIV, POD, flow meandering, fuel rod assembly, tight lattice, narrow gap, coolant hydrodynamics
Abstract
Fuel rod assemblies with dense packing are promising from the point of increasing the conversion rate and heat transfer in small modular reactors. The main feature of the flow in the dense packing is the formation of quasi-periodic large-scale velocity pulsations in a gap between fuel rods, which intensify mixing between the subchannels and greatly increase heat transfer between the fuel rods and the coolant. The large-scale pulsations relate directly to the pitch-to-diameter (P/D) ratio of the rod bundle and the Reynolds number (Re). In this work, the unsteady flow structure in a gap between a flat wall and three rods with a relative pitch P/D = 1.077 is experimentally studied using the PIV method with high time resolution. The averaged flow characteristics, including the three-dimensional ones, are presented. The influence of the Re number on flow oscillations in the gap was studied. The spatial most energy-intensive flow modes were analyzed using the POD method. The results obtained indicate the presence of several traveling waves propagating along the flow. Modulation of flow oscillations in the gap was detected. These investigation results are in good agreement with the results of other authors.
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