Measurements of turbulent flow in a large-scale model of a 37-rod bundle

Highlights: • Turbulence in a rod bundle was documented experimentally in detail. • The Reynolds number has a measurable effect on different properties. • The gap vortex street forms close to the inlet. - Abstract: The turbulent flow in the subchannels around an outer rod of a scaled up (12.9:1) model of a 60° section of the CANDU reactor 37-rod bundle with a pitch-to-diameter ratio of 1.149 was documented for three bulk Reynolds numbers (50,000, 100,000 and 130,000). Reported results include measurements of the mean axial velocity, the Reynolds stresses, the turbulent kinetic energy, the anisotropy tensor components, the integral length scale, the Taylor microscale, the Kolmogorov microscale, the wall shear stress, the friction factor and the characteristics of the gap vortex street forming in the vicinity of a rod-wall gap. In general, normalised turbulence properties showed some weak dependence on Reynolds number, whereas the normalised Strouhal number, convection speed and wavelength of the vortex street were insensitive to the Reynolds number. The gap vortex street was found to form fairly close to the rod-bundle inlet, which was fitted with an endplate. The objective of this work was to elucidate the effect of Reynolds number on the turbulence properties and the vortex streets that form in tightly-packed rod bundle flows. The reported measurements have been documented in sufficient detail to serve as a reliable database for the validation of computational fluid dynamics analyses of such flows.