Armel Don is up next – Tuesday at 10am!

Come hear Armel Don present his thesis seminar on “Structure of Turbulent Flow in a Rod Bundle”.

OMEGA is offering tea, coffee and cookies. We’ll be in CBY B012 at 10:00am.  The abstract of Armel’s talk is below.


The core of the CANadian Deuterium Uranium (CANDU) nuclear reactor consists of several pressure tubes containing bundles of fuel elements (“rods”) stacked end to end. The fuel rods are cooled by liquid coolant (heavy water) flowing axially in the interconnected subchannels formed by the rods. The thermal-hydraulic performance of the reactor, and particularly the surface temperature of the rods and the temperature of the coolant depend strongly on the turbulent flow structure in the subchannels.

Typically, the Reynolds number of a CANDU reactor running at full power is about half a million. During start-up or shut down, the Reynolds number drops to a much lower value and tends to fluctuate. Although a large number of experimental and computational studies have examined flows in rod bundles, the effect of Reynolds number on the structure of turbulence and the development of vortex networks have not been documented sufficiently.

This experiment aims at investigating experimentally the structure of turbulent flow in the subchannels of a large scale, 60o section of a CANDU 37-rod bundle at Reynolds numbers equal to 50,000, 100,000 and 130,000. The mean flow distribution, the turbulent kinetic energy, the Reynolds stresses, coherent structure characteristics and other turbulence indicators were measured using constant temperature hot-wire anemometry. It was demonstrated that coherent structures, whose generation is attributed to the gap instability mechanism and which form a vortex network, originated very close to the rod bundle inlet. The convection speed of the vortex network increased with bulk velocity, whereas the spacing between the coherent vortices remained unaffected.

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