RESUMODesde a descoberta dos raios-x, em 1895, a radiação ionizante é aplicada em diversos setores da sociedade, tais como medicina, indústria, segurança, construção civil, engenharia e pesquisa, no entanto, a população em geral desconhece tanto as aplicações quanto seus riscos e seus benefícios. Pode-se constatar que a maioria das pessoas associam os termos "radiação" e "energia nuclear" à bomba atômica ou ao câncer, isto muito provavelmente devido a aplicações bélicas e a maneira sigilosa como a radioatividade fora tratada no passado. Desta forma, torna-se necessário esclarecer a população sobre os principais aspectos relativos às aplicações, aos riscos e aos benefícios associados. Tais conhecimentos podem ser disseminados nas escolas. A legislação brasileira para a educação básica prevê apresentação de temas como energia nuclear e radioatividade aos alunos de ensino médio. No entanto, alguns fatores dificultam tal prática educacional, a saber: poucas horas aula, livros didáticos não abordam o assunto, conceitos prévi-os obtidos na mídia, dificuldade de tratar o assunto em sala de aula, fobia, etc. Uma solução seria a aproximação entre as escolas e as instituições que empregam tecnologias envolvendo radioatividade, o que permitiria aos alunos conhecer as práticas, a proteção radiológica associada, bem como os riscos e benefícios para a sociedade. Atualmente, com a crescente aplicação da radiação ionizante, sobretudo em medicina, é necessário desmistificar o uso da radioatividade.Palavras-chave: Radioatividade, proteção radiológica, escola

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Free-surface flows occur in several problems in hydrodynamics, such as fuel or water sloshing in tanks, waves breaking in ships, offshore platforms, harbors, and coastal areas. The computation of such highly nonlinear flows is challenging, since free-surfaces commonly present merging, fragmentation, and breaking parts, leading to the use of interface-capturing Eulerian approaches. In such methods the surface between two fluids is captured by the use of a marking function, which is transported in a flow field. In this work we discuss computational techniques for efficient implementation of 3D incompressible streamline-upwind/Petrov–Galerkin (SUPG)/pressure-stabilizing/Petrov–Galerkin finite element methods to cope with free-surface problems with the volume-of-fluid method (Elias, and Coutinho, 2007, “Stabilized Edge-Based Finite Element Simulation of Free-Surface Flows,” Int. J. Numer. Methods Fluids, 54, pp. 965–993). The pure advection equation for the scalar marking function was solved by a fully implicit parallel edge-based SUPG finite element formulation. Global mass conservation is enforced, adding or removing mass proportionally to the absolute value of the normal velocity of the interface. We introduce parallel edge-based data structures, a parallel dynamic deactivation algorithm to solve the marking function equation only in a small region around the interface. The implementation is targeted to distributed memory systems with cache-based processors. The performance and accuracy of the proposed solution method is tested in the simulation of the water impact on a square cylinder and in the propagation of a solitary wave.

Complex flows involving waves and free-surfaces occur in several problems in hydrodynamics, such as fuel or water sloshing in tanks, waves breaking in ships, offshore platforms motions, wave action on harbors and coastal areas. The computation of such highly nonlinear flows is challenging since waves and free-surfaces commonly present merging, fragmentation and cusps, leading to the use of interface capturing Arbitrary Lagrangian-Eulerian (ALE) approaches. In such methods the interface between the two fluids is captured by the use of a marking function that is transported in a flow field. In this work we simulate these problems with a 3D incompressible SUPG/PSPG parallel edge-based finite element flow solver associated to the Volume-of-Fluid (VOF) method. The hyperbolic equation for the transport of the marking function is also solved by a fully implicit parallel edge-based SUPG finite element formulation. Global mass conservation is enforced adding or removing mass proportionally to the absolute value of the normal velocity at the interface. All those techniques were successfully implemented in a computational code, which has been suitably used to carry out several studies. The performance and accuracy of the proposed solution method is tested in the simulation waves and in the interaction between waves and a semisubmersible structure. Results count on the establishment of a relaxation zone close to the domain outflow, which partially absorbs incoming waves, avoiding their reflection.

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.