Abstract
A CFD analysis has been carried out to study the thermal-hydraulic behavior of liquid metal coolant in a fuel assembly of triangular lattice. In order to obtain fast and accurate results, the isotropic two-equation RANS approach is often used in nuclear engineering applications. A different approach is provided by Non-Linear Eddy Viscosity Models (NLEVM), which try to take into account anisotropic effects by a nonlinear formulation of the Reynolds stress tensor. This approach is very promising, as it results in a very good numerical behavior and in a potentially better fluid flow description than classical isotropic models. An Anisotropic Shear Stress Transport (ASST) model, implemented into a commercial software, has been applied in previous studies, showing very trustful results for a large variety of flows and applications. In the paper, the ASST model has been used to perform an analysis of the fluid flow inside the fuel assembly of the ALFRED lead cooled fast reactor. Then, a comparison between the results of wall-resolved conjugated heat transfer computations and the results of a decoupled analysis using a suitable thermal wall-function previously implemented into the solver has been performed and presented.
Highlights
In order to obtain fast and accurate results, the isotropic eddy-viscosity RANS approach is often used in nuclear engineering applications: in particular, the k–ε model, k–ω model and SST model are examples of isotropic two-equations models widely used
A different approach is provided by Non-Linear Eddy Viscosity Models (NLEVM), which try to take into account anisotropic effects by a nonlinear formulation of the Reynolds stress tensor
First of all it is of primary importance to verify that the used models are able to correctly reproduce the main features of the triangular lattice flow
Summary
In order to obtain fast and accurate results, the isotropic eddy-viscosity RANS approach is often used in nuclear engineering applications: in particular, the k–ε model, k–ω model and SST model are examples of isotropic two-equations models widely used. As known from the literature, these models can fail when dealing with complex flows, especially when secondary flows are important Another approach is provided by Reynolds Stress Models (RSM), in which all the components of the Reynolds stress tensor are directly computed: this makes them suitable for anisotropic flows treatment but, as main drawback, it requires an expensive computational effort and potentially suffers numerical stability problems. A different approach is provided by Non-Linear Eddy Viscosity Models (NLEVM), which try to take into account anisotropic effects by a nonlinear formulation of the Reynolds stress tensor. This approach is very promising, as it results in a very good numerical behaviour and in a potentially better fluid flow description if compared with classical isotropic models. A CFD study focused on the application of the abovementioned approaches has been carried out on the liquid metal flow within the fuel assembly of the ALFRED lead cooled fast reactor
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