Numerical modeling of neutron transport - finite volume method, residual distribution schemes
Some remarks concerning stabilization techniques for convection--diffusion problems
There are many methods and approaches to solving convection--diffusion problems. For those who want to solve such problems the situation is very confusing and it is very difficult to choose the right method. The aim of this short overview is to provide basic guidelines and to mention the common features of different methods. We place particular emphasis on the concept of linear and non-linear stabilization and its implementation within different approaches.
On the approximation of the non-autonomous non-linear Riemann problem
In this paper we study conservation laws with spatially-varying flux functions. We give a survey of some schemes (based on finite volume methods) to solve non-autonomous conservation laws of the form . Numerical experiments are presented.
Numerical modelling of river flow (numerical schemes for one type of nonconservative systems
In this paper we propose a new numerical scheme to simulate the river flow in the presence of a variable bottom surface. We use the finite volume method, our approach is based on the technique described by D. L. George for shallow water equations. The main goal is to construct the scheme, which is well balanced, i.e. maintains not only some special steady states but all steady states which can occur. Furthermore this should preserve nonnegativity of some quantities, which are essentially nonnegative...
High resolution schemes for open channel flow
One of the commonly used models for river flow modelling is based on the Saint-Venant equations - the system of hyperbolic equations with spatially varying flux function and a source term. We introduce finite volume methods that solve this type of balance laws efficiently and satisfy some important properties at the same time. The properties like consistency, stability and convergence are necessary for the mathematically correct solution. However, the schemes should be also positive semidefinite...
Numerical modelling of flow in lower urinary tract using high-resolution methods
We propose a new numerical scheme based on the finite volumes to simulate the urethra flow based on hyperbolic balance law. Our approach is based on the Riemann solver designed for the augmented quasilinear homogeneous formulation. The scheme has general semidiscrete wave–propagation form and can be extended to arbitrary high order accuracy. The first goal is to construct the scheme, which is well balanced, i.e. maintains not only some special steady states but all steady states which can occur....
Numerical modeling of neutron flux in hexagonal geometry
Isogeometric analysis for fluid flow problems
The article is devoted to the simulation of viscous incompressible fluid flow based on solving the Navier-Stokes equations. As a numerical model we chose isogeometrical approach. Primary goal of using isogemetric analysis is to be always geometrically exact, independently of the discretization, and to avoid a time-consuming generation of meshes of computational domains. For higher Reynolds numbers, we use stabilization techniques SUPG and PSPG. All methods mentioned in the paper are demonstrated...
Three-dimensional numerical model of neutron flux in hex-Z geometry
We present a method for solving the equations of neutron transport with discretized energetic dependence and angular dependence approximated by the diffusion theory. We are interested in the stationary solution that characterizes neutron fluxes within the nuclear reactor core in an equilibrium state. We work with the VVER-1000 type core with hexagonal fuel assembly lattice and use a nodal method for numerical solution. The method effectively combines a whole-core coarse mesh calculation with a more...
Gradient-free and gradient-based methods for shape optimization of water turbine blade
The purpose of our work is to develop an automatic shape optimization tool for runner wheel blades in reaction water turbines, especially in Kaplan turbines. The fluid flow is simulated using an in-house incompressible turbulent flow solver based on recently introduced isogeometric analysis (see e.g. J. A. Cotrell et al.: Isogeometric Analysis: Toward Integration of CAD and FEA, Wiley, 2009). The proposed automatic shape optimization approach is based on a so-called hybrid optimization which combines...
Modelování dopravního proudu – složitý příběh jednoho typu matematických modelů
Stručná historie metody konečných objemů
Setkání učitelů matematiky všech typů a stupňů škol
Informace o konání konference.
Consistent streamline residual-based artificial viscosity stabilization for numerical simulation of incompressible turbulent flow by isogeometric analysis
In this paper, we propose a new stabilization technique for numerical simulation of incompressible turbulent flow by solving Reynolds-averaged Navier-Stokes equations closed by the SST - turbulence model. The stabilization scheme is constructed such that it is consistent in the sense used in the finite element method, artificial diffusion is added only in the direction of convection and it is based on a purely nonlinear approach. We present numerical results obtained by our in-house incompressible...
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