A CFD approach to the atmospheric dispersion of radionuclides in the vicinity of NPPs

Sampaio, Paulo Augusto Berquó de; A.G., Milton; Lapa, Celso Marcelo Franklin

doi:10.1016/j.nucengdes.2007.05.009

Cited by 28 publications

(20 citation statements)

References 14 publications

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“…It is also needed to prevent undesirable pressure oscillations when equal order interpolations for velocity and pressure are used. In turbulent flow, small-scales physics become crucial, and, the beneficial effects of stabilization may be used to numerically generate eddy-viscosities needed in LES (see [33][34][35][36][37][38][39]). Nevertheless, according to Bazilevs et al [40], traditional eddy viscosities are inefficient in representing fine scales dissipation mechanisms and introduce inconsistencies.…”

Section: Introductionmentioning

confidence: 99%

Residual-based variational multiscale simulation of free surface flows

et al. 2010

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In this work we apply the residual-based variational multiscale method (RB-VMS) to the volume-of-fluid (VOF) formulation of free-surface flows. Using this technique we are able to solve such problems in a Large Eddy Simulation framework. This is a natural extension of our Navier-Stokes solver, which uses the RB-VMS finite element formulation, edge-based data structures, adaptive time step control, inexact Newton solvers and supports several parallel programming paradigms. The VOF interface capturing variable is advected using the computed coarse and fine scales velocity field. Thus, the RB-VMS technique can be readily applied to the free-surface solver with minor modifications on the implementation. We apply this technique to the solution of two problems where available data indicate complex free-surface behavior. Results are compared with numerical and experimental data and show that the present formulation can achieve good accuracy with minor impacts on computational efficiency.Keywords Variational multiscale method · Edge-based computations · Volume of fluid · Free surface flows

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Section: Introductionmentioning

confidence: 99%

Residual-based variational multiscale simulation of free surface flows

et al. 2010

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“…In turbulent flow, small-scales physics become crucial and the beneficial effects of stabilization may be used to generate numerically eddy viscosities needed in LES [7][8][9][10]. Practical examples of such an approach, in fluid-structure interaction, dispersion of radionuclides in nuclear power plants and density currents may be found in [11][12][13]. In these, different numerical implementations are present (space-time, semi-discrete, fully coupled, segregated) and additional computational devices, such as mesh adaptation or discontinuity-capturing is often employed.…”

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confidence: 99%

Edge‐based finite element implementation of the residual‐based variational multiscale method

Lins

Elias

Guerra

et al. 2008

Numerical Methods in Fluids

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SUMMARYIn this work we extend our edge-based stabilized finite element incompressible flow solver to turbulence modeling with the residual-based variational multiscale (RB-VMS) method. Using the advective-form of the convection term of the Navier-Stokes equations, RB-VMS is implemented as a straightforward extension of standard stabilized methods with a modified advective velocity. This requires minimum modification of the existing highly optimized code. Two test cases were solved to assess accuracy and performance of the present implementation. First, the laminar incompressible flow past a circular cylinder at Re = 100 and second, the fully turbulent incompressible flow in a lid-driven cubic cavity at Re=12 000. Comparisons were made with standard stabilized finite element formulations, highly resolved numerical simulations and experimental data. Results have shown that the present implementation is able to achieve reasonable accuracy without performance degradation in different flow regimes.

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“…The synchronization scheme, introduced by De Sampaio in [2,3], can be extended to problems where other physical phenomena are also present, as transport of energy and of the concentrations of radionuclide [7], for instance.…”

Section: Local Time Steps and Synchronizationmentioning

confidence: 99%

A second‐order time accurate finite element method for quasi‐incompressible viscous flows

Sampaio¹,

Gonçalves²

2010

Numerical Methods in Fluids

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SUMMARYA finite element method for quasi-incompressible viscous flows is presented. An equation for pressure is derived from a second-order time accurate Taylor-Galerkin procedure that combines the mass and the momentum conservation laws. At each time step, once the pressure has been determined, the velocity field is computed solving discretized equations obtained from another second-order time accurate scheme and a least-squares minimization of spatial momentum residuals. The terms that stabilize the finite element method (controlling wiggles and circumventing the Babuska-Brezzi condition) arise naturally from the process, rather than being introduced a priori in the variational formulation. A comparison between the present second-order accurate method and our previous first-order accurate formulation is shown. The method is also demonstrated in the computation of the leaky-lid driven cavity flow and in the simulation of a crossflow past a circular cylinder. In both cases, good agreement with previously published experimental and computational results has been obtained.

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A CFD approach to the atmospheric dispersion of radionuclides in the vicinity of NPPs

Cited by 28 publications

References 14 publications

Residual-based variational multiscale simulation of free surface flows

Residual-based variational multiscale simulation of free surface flows

Edge‐based finite element implementation of the residual‐based variational multiscale method

A second‐order time accurate finite element method for quasi‐incompressible viscous flows

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