SANAA, Rolex Learning Center

En el curso 2012-2013 el Laboratorio de Crítica centró su atención en el Rolex Learning Center de l´Ecole Polytechnique Fédérale de Lausanne en Suiza, obra de indudable interés del estudio japonés SANAA que constituye en sí misma un auténtico experimento y, consecuentemente, un objeto de observación apropiado para el estudio dentro del Laboratorio. En octubre de 2012 se realizó un viaje para visitar el edificio y, posteriormente, se realizaron por parte de los alumnos, ejercicios críticos y experimentos de los que en esta publicación aparece una muestra representativa. También se recogen en este libro, publicado gracias al apoyo de la ETSAM dentro de su colección de Texto Académicos, algunas aportaciones externas como el escrito y los dibujos del arquitecto Javier Aguilera, así como otros textos de antiguos alumnos del Laboratorio como Rosa Ballester, Berta González Salinero o Daniel Sacristán que, además han contribuido decisivamente en la edición. Se incluye, asimismo, un artículo de Eider Holgado, alumna de doctorado que está realizando su tesis, dentro del G.I. ARKRIT.

Experimental and numerical assessment of the aeroelastic stability of blade pair packages

The stabilizing effect of grouping rotor blades in pairs has been assessed both, numerically and experimentally. The bending and torsion modes of a low aspect ratio high speed turbine cascade tested in the non-rotating test facility at EPFL (Ecole Polytechnique Fédérale de Lausanne) have been chosen as the case study. The controlled vibration of 20 blades in travelling wave form was performed by means of an electromagnetic excitation system, enabling the adjustement of the vibration amplitude and inter blade phase at a given frequency. Unsteady pressure transducers located along the blade mid-section were used to obtain the modulus and phase of the unsteady pressure caused by the airfoil motion. The stabilizing effect of the torsion mode was clearly observed both in the experiments and the simulations, however the effect of grouping the blades in pairs in the minimum damping at the tested frequency was marginal in the bending mode. A numerical tool was validated using the available experimental data and then used to extend the results at lower and more relevant reduced frequencies. It is shown that the stabilizing effect exists for the bending and torsion modes in the frequency range typical of low-pressure turbines. It is concluded that the stabilizing effect of this configuration is due to the shielding effect of the pressure side of the airfoil that defines the passage of the pair on the suction side of the same passage, since the relative motion between both is null. This effect is observed both in the experiments and simulations.