Direct numerical and large eddy simulations in nuclear applications

Grötzbach, G.; Wörner, Martin

doi:10.1016/s0142-727x(99)00012-0

Cited by 65 publications

(15 citation statements)

References 93 publications

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“…Since the temperature profiles of Fig. 6 become visibly more asymmetric as R increases, (11) dictates that wT increases as well, at least for σ = 5 and this range of R. Our computed values of wT indeed rise with R in this regime, though not in all regimes.…”

Section: Temperature Profilesmentioning

confidence: 55%

Convection driven by internal heating

Goluskin

Spiegel

2012

Physics Letters A

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Two-dimensional direct numerical simulations are conducted for convection sustained by uniform internal heating in a horizontal fluid layer. Top and bottom boundary temperatures are fixed and equal. Prandtl numbers range from 0.01 to 100, and Rayleigh numbers (R) are up to 5x10^5 times the critical R at the onset of convection. The asymmetry between upward and downward heat fluxes is non-monotonic in R. In a broad high-R regime, dimensionless mean temperature scales as R^{-1/5}. We discuss the scaling of mean temperature and heat-flux-asymmetry, which we argue are better diagnostic quantities than the conventionally used top and bottom Nusselt numbers.Comment: 14 pages, 8 figures, 6 videos; to appear in Physics Letters A; Color and grayscale versions provided; v2: ancillary videos fixe

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Section: Temperature Profilesmentioning

confidence: 55%

Convection driven by internal heating

Goluskin

Spiegel

2012

Physics Letters A

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“…[21] The use of approximate boundary conditions results in lower calculation costs (proportional to Re 0.6 [see Piomelli and Balaras, 2002]), since the grid size in y is Reynolds-number independent. The existence of an equilibrium layer results in a logarithmic law [Deardorff, 1970;Schumann, 1975;Grötzbach, 1987;Piomelli et al, 1989]. Knowing the average velocity in the outer layer (and, in particular, at the first grid point), one can relate it to the friction velocity u t by solving…”

Section: Wall Boundary Conditionsmentioning

confidence: 99%

Large‐eddy simulation of oscillating boundary layers: Model comparison and validation

Radhakrishnan

Piomelli

2008

J. Geophys. Res.

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[1] Large-eddy simulations of oscillating boundary layers over smooth and rough walls in the fully turbulent regime have been carried out. Several models for the unresolved subgrid-scale (SGS) stresses are compared, as well as different approximate treatments of the wall layer, where none of the momentum-transporting eddies is resolved. The simulations show that the use of advanced SGS models coupled with approximate boundary conditions can predict the flow successfully. Dynamic SGS eddy-viscosity models yield more accurate results than the fixed-coefficient one, which yields an excessively large SGS eddy viscosity, damping the wall-normal fluctuations. The shifted logarithmic-law approximate boundary condition, which accounts for the inclination of the near-wall eddies, results in prediction of the wall stress within 3% of the experimental data throughout the cycle. The standard logarithmic law also gives adequate results, with a maximum error of 6%. A modification of the rough-wall logarithmic law that accounts for transitional roughness effects was also tested; at this Reynolds number, however, this correction made little difference in the numerical results.

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“…Figure 1(a) shows the IH configuration we consider here: a horizontal layer of fluid, bounded above and below by plates of fixed and equal temperatures, that is subject to constant and uniform heating throughout its volume. These boundary conditions are especially relevant to systems that are cooled above and below, such as liquid metal batteries (Shen & Zikanov 2015) or overreactions in nuclear reactor accidents (Asfia & Dhir 1996;Nourgaliev, Dinh & Sehgal 1997;Grötzbach & Wörner 1999). IH convection in this configuration and others is reviewed by Goluskin (2015).…”

Section: Introductionmentioning

confidence: 99%

Penetrative internally heated convection in two and three dimensions

Goluskin

Poel

2016

J. Fluid Mech.

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Convection of an internally heated fluid, confined between top and bottom plates of equal temperature, is studied by direct numerical simulation in two and three dimensions. The unstably stratified upper region drives convection that penetrates into the stably stratified lower region. The fraction of produced heat escaping across the bottom plate, which is one half without convection, initially decreases as convection strengthens. Entering the turbulent regime, this decrease reverses in two dimensions but continues monotonically in three dimensions. The mean fluid temperature, which grows proportionally to the heating rate ($H$) without convection, grows proportionally to $H^{4/5}$ when convection is strong in both two and three dimensions. The ratio of the heating rate to the fluid temperature is likened to the Nusselt number of Rayleigh-B\'enard convection. Simulations are reported for Prandtl numbers between 0.1 and 10 and for Rayleigh numbers (defined in terms of the heating rate) up to $5\times10^{10}$.Comment: 12 pages, 5 figures, 3 tables, 1 movie; v2: text updated, figures and tables added, figure 4 correcte

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Direct numerical and large eddy simulations in nuclear applications

Cited by 65 publications

References 93 publications

Convection driven by internal heating

Convection driven by internal heating

Large‐eddy simulation of oscillating boundary layers: Model comparison and validation

Penetrative internally heated convection in two and three dimensions

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