Computational Fluid Dynamic Studies of Vortex Amplifier Design for the Nuclear Industry—I. Steady-State Conditions

Abstract

In this study the effects of changes to the geometry of a vortex amplifier are investigated using computational fluid dynamics (CFD) techniques, in the context of glovebox operations for the nuclear industry. These investigations were required because of anomalous behavior identified when, for operational reasons, a long-established vortex amplifier design was reduced in scale. The aims were (i) to simulate both the anomalous back-flow into the glovebox through the vortex amplifier supply ports, and the precessing vortex core in the amplifier outlet, then (ii) to determine which of the various simulated geometries would best alleviate the supply port back-flow anomaly. Various changes to the geometry of the vortex amplifier were proposed; smoke and air tests were then used to identify a subset of these geometries for subsequent simulation using CFD techniques. Having verified the mesh resolution was sufficient to reproduce the required effects, the code was then validated by comparing the results of the steady-state simulations with the experimental data. The problem is challenging in terms of the range of geometrical and dynamic scales encountered, with consequent impact on mesh quality and turbulence modeling. The anomalous nonaxisymmetric reverse flow in the supply ports of the vortex amplifier has been captured and the mixing in both the chamber and the precessing vortex core has also been successfully reproduced. Finally, by simulating changes to the supply ports that could not be reproduced experimentally at an equivalent cost, the geometry most likely to alleviate the back-flow anomaly has been identified.

Computational Fluid Dynamic Studies of Vortex Amplifier Design for the Nuclear Industry—II. Transient Conditions

“…The results of smoke and air experiments, the modeling of the VXA geometry, the verification and validation of the computational mesh, and the results of the steady-state CFD simulations have been documented in Paper1 [2]. Although the results of these simulations successfully reproduced the required steady-state behavior in both the supply and outlet ports, temporal flow regimes within these regions were not resolved.…”

“…The principle of operation of the VXA is explained in the accompanying paper [2], hereafter referred to as "Paper1. "…”

“…The Baseline (BSL) turbulence model was used in the steadystate investigations of Paper1 [2] and the resulting flow structure and convergence appeared to capture evidence of the known precessing vortex core, along with nonaxisymmetric boundary flows in the chamber and exit port. That result implied that the flow structures in the four inlet ports were not identical, but affected by the vortex.…”

“…In doing so, the ultimate objective was to develop a prototype VXA unit capable of reducing air leakage back into the glovebox without the use of an additional structure such as a cowl or distancing chamber, and hence to reduce the cost of keeping a glovebox inerted. Following a study of steady-state flows in various candidate geometries (see Paper1 [2]) a prototype geometry was established that, when physically tested on site, reduced inert gas usage to 25% of the scaled mini-VXA units [4].…”

Stochastic regimes in very-low-frequency fluidic oscillator

“…• The other until recently serious problem associated with known vortex amplifiers is the fact that their control input pressure must be higher than the pressure in the supply terminal [13,14]. This would obviously lead to substantial complication in the design of the anti-parallel circuit, at least if solutions are sought among circuits exhibiting the configuration similarity ΔU G < ΔU S of the electronic circuits discussed in Sect.…”