Analysis Of Turbulence-Induced Crossflow And Coolant Mixing Under Various Flow Interventions In Rod Bundle Geometries

Abstract

In recent times efforts have been made to understand turbulence-induced crossflow and coolant mixing in fuel rod bundles. This phenomenon in nuclear reactors is essential for optimizing heat removal. This study in vestigates the contribution of fuel bundles with split vane, swirl vane, spacer grid and no spacer grid to the development of secondary flows, turbulence, and crossflow. High-fidelity simulations were employed to quantify axial and lateral flow redistribution, turbulent kinetic energy (TKE) evolution, dissipation behaviour, vorticity and velocity distribution patterns across bundle subchannels. Results show that vane-type spacers substantially intensify crossflow by generating strong streamwise vortices that persist downstream, with swirl vanes producing the most sustained mixing effects. Turbulence metrics reveal elevated TKE, localized production peaks, and enhanced dissipation in all vane-equipped configurations, consistent with classical energy cascade behaviour. Collectively, the findings demonstrate that fuel rod bundles equipped with flow mixing interventions induce turbulence which significantly improves crossflow and coolant mixing, providing a foundation for improved crossflow correlation development and supporting the design of next-generation high-performance rod bundle assemblies.