Caractérisation des phénomènes complexes de l’écoulement turbulent tridimensionnel avec transfert de chaleur à travers une série d’aubes.

Abstract

The present work is a numerical study of the three dimensional turbulent steady or unsteady flow, with or without heat transfer, of an incompressible fluid through a series of blades similar to those used in turbomachines. In the first part, the study addresses the steady turbulent flow through a series of 60 blades fixed on an annular structure (stator). The contribution within the framework of the present project is the exploration of the sensitivity of the dynamical behaviour of the flow to the variations of the turbulence intensity at the domain inlet. The effects on the fields of velocity, pressure, turbulent kinetic energy and turbulent viscosity are examined. The turbulence effects on the flow are taken into account using the standard k-ε model in conjunction with,as a near-wall treatment, the standard wall function. The second and more important part is a study of the three-dimensional turbulent incompressible and unsteady flow with and without heat transfer through a plane blade cascade comprised of six identical blades. This configuration is similar to that studied experimentally by Adjlout and Dixon (Journal of Turbomachinery, 114, pp.191-198, 1992). Two cases are considered: the flow without heat transfer through the blade cascade with a stagger angle of 0°; the flow with heat transfer through the blade cascade with a stagger angle of 25°. This is the angle between a line normal to the pitch direction and a line parallel to direction of the chord. The turbulence effect on the flow is taken into account using the large eddy simulation approach. 3D mean and filtered fields of velocity, pressure, turbulent kinetic energy, subgrid turbulent viscosity and temperature are analysed. Also contours of friction and pressure coefficients and Nusselt number on the surface of the blades and the casing are discussed. Particular attention is paid to the secondary flows induced between blades and at the blade/casing junction and their impact on the dynamical and thermal behaviours.