A Numerical Investigation of Swirling Turbulent Buoyant Jets at Transient Reynolds Numbers

Taub, G. N.; Lee, H.; Balachandar, S.

doi:10.2514/6.2010-1362

Cited by 2 publications

(3 citation statements)

References 7 publications

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“…When high-order numerical methods are used, along with a well-resolved spatial and temporal scales, the calculations compare quite favorably with experimental data, to the point that many authors go as far as considering the output as good as experimental data [Moet et al, 2004;Freitag and Klein, 2005;Duraisamy and Lele, 2006;Afgan, 2007;Bonaldo, 2007;Busch, Ryan, and Sheard, 2007;Walther et al, 2007;Taub et al, 2010].…”

Section: Direct Numerical Simulation (Dns) Methodsmentioning

confidence: 94%

“…Although the DNS output compares excellently with experimental data [Moet et al, 2004;Freitag and Klein, 2005;Duraisamy and Lele, 2006;Facciolo, 2006;Afgan, 2007;Bonaldo, 2007;Busch, Ryan, and Sheard, 2007;Walther et al, 2007;Taub et al, 2010], it was not selected because it is computationally expensive. For example, it requires that the number of computational operations is on the order of Re 3 [Wikipedia, 2011b].…”

Section: ]!mentioning

confidence: 99%

“…Further, for a 3D domain, the number of required cells is Re 9/4 [Afgan, 2007;Sodja, 2007;Stein, 2009] to as high as Re 11/4 [Taub et al, 2010]. By comparison, the number of computational time steps, N, for LES vs. DNS [Sodja, 2007] shows that 1/ 4…”

Section: ]!mentioning

confidence: 99%

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Swirling jets for the mitigation of hot spots and thermal stratification in the VHTR lower plenum.

Rodríguez¹

2011

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The literature indicates that a prismatic-core very high temperature reactor can experience thermal stratification and hot spot issues in the lower plenum (LP). This research hypothesizes that the complex thermalhydraulic phenomena in the LP requires a sophisticated computational fluid dynamics (CFD) code with state-of-the-art turbulence models and advanced swirling jet technology to mitigate the two issues. The primary research goals were to increase the heat transfer and mixing capacity of swirling jets, extend swirling jet theory, and to apply those advancements for the mitigation of the thermalhydraulic issues. First, it was demonstrated that the Fuego CFD code successfully modeled a set of key LP thermalhydraulic phenomena. Thereafter, a helicoid vortex swirl model was developed to investigate the impact of the swirl number (S) on mixing and heat transfer. The development of azimuthal and axial velocities that are solely functions of S permitted the analysis of the central recirculation zone's (CRZ) impact on the LP flow field. At this point, several characteristics were found in common between the helicoid vortex and other axisymmetric, Newtonian, incompressible vortices found in the literature. This observation resulted in a more fundamental understanding of how vortices behave, and which traits can be exploited for the purpose of maximizing heat transfer and mixing. Because the CRZ is a strong function of the azimuthal and axial velocities, shaping those velocity profiles had a substantial impact. Eventually, this led to the discovery that vortices may be expressed as alternating series that expand geometrically with odd exponents. This helped corroborate that the 15 axisymmetric vortices discussed in this research are part of a vortex family with seven common traits. This also led to the development of new vortices that are based on one or two series terms that satisfy the Navier-Stokes equations and conservation of mass. In addition, the impact of Reynolds number and swirl decay were explored in order to further quantify their impact. Finally, the above theories and modeling insights were applied towards a comprehensive set of LP calculations that showed that the swirling jets mitigated the entrainment and hot spot issues, while resulting in a reasonable pressure drop. Contents

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