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Reynolds stress distribution downstream of a turbine cascade

1992; Elsevier BV; Volume: 5; Issue: 3 Linguagem: Inglês

10.1016/0894-1777(92)90079-k

1879-2286

A. Perdichizzi, Marina Ubaldi, Pietro Zunino,

Heat Transfer Mechanisms

The results are presented of an experimental investigation on the three-dimenstional turbulent flow developing downstream of a turbine cascade. The cascade has an aspect ratio of 1.05 and the flow turning is about 84°. Measurements were performed in four planes located respectively at 10, 30, 54, and 90% of an axial chord downstream of the blade trailing edge. The mean velocity field and the energy loss coefficient distributions were obtained by five-hole pressure probe measurements, while the six Reynolds stress tensor components were determined by using hot-wire probes. The tests were made at low-velocity conditions, corresponding to an isentropic outlet Mach number of 0.3. The results show that high turbulence levels, both for normal and shear stress components, are associated with regions affected by secondary vortices. The evolution of the Reynolds stress distributions follows closely the development of secondary vortices, showing that convection plays a significant role in determining Reynolds stress distributions. In the first plane turbulence was found to be highly anisotropic, but in the following planes a clear trend to isotropy can be detected. The local production of turbulent kinetic energy in the four measuring planes is also presented. The eddy viscosity distributions, calculated independently from the three shear stresses and the corresponding mean strain components, show the vectorial nature of this quantity and put in evidence some severe limitations to the applicability of the eddy viscosity hypothesis to these complex flows. The results presented can be used as reference data to validate Navier-Stokes numerical methods for three-dimensional flows and in particular to improve turbulence models for turbomachinery applications.