NON LINEAR EDDY VISCOSITY MODEL APPLIED TO U-BEND INDUSTRIAL GEOMETRY

The use of numerical approach to support design and product development on industrial applications is nowadays quite widespread. Many industrial applications involve turbulent fluid flows, whose modeling still represents the bottleneck for a wider usage of numerical methods. Indeed, the application of the CFD approach to industrial problem has a number of high demanding requirements since it must deal with relatively short computational time, high geometrical complexity and high Reynolds numbers. These industrial constrains nowadays may be partially faced through RANS approach even if poor capability in predicting accurately the fluid dynamics of complex flows still represents their well known weakness. The aim of this work is to provide a model able to improve the prediction of the flow field in complex flows of industrial interest, with special attention to the presence of strong curvature. Therefore, in order to obtain an increase in the accuracy of the results compared with traditional k-e models, the implementation of a two-equation Non Linear Eddy Viscosity Model (NLEVM) is proposed. The quadratic formulation of this model has already been validated by experimental and DNS data from literature. In the present work the cubic formulation of this model is applied to a strong-curve-geometry of industrial interest. The data are obtained through an experimental facility developed by the CFDLab of the Department of Energy at Politecnico di Milano. The measures are taken in cooperation with the Combustion and Optical Diagnostic Laboratory research group. The comparison between experimental and numerical data is carried out downstream a strong curvature by looking at mean axial velocity profiles and reattachment point prediction.