Advanced open rotor far-field tone noise

An extensive analysis of the far-field tonal noise produced by an advanced open rotor is presented. The basis of the work is analytical methods which have been developed to predict the tonal noise generated by several different mechanisms. Also to provide further insight and validation, an in-depth analysis of rig-scale wind tunnel measurements and Computational Fluid Dynamics (CFD) data has been carried out.The loading noise produced by a propeller operating at angle of attack is formulated modeling the blades as a cascade of a two-dimensional flat plates. The simplified geometry enables the prediction of rotor-alone tones with a reduced computer processing time. The method shows a good ability to predict the relative change of the sound pressure level with changes of the angle of attack.The radiated sound field caused by aerodynamic interactions between the two blade rows is investigated. A hybrid analytical/computational method is developed to predict the tonal noise produced by the interaction between the front rotor viscous wakes and the rear rotor. The method assumes a Gaussian wake profile whose characteristics are determined numerically in the inter-rotor region and propagated analytically to the downstream blade row. A cross validation of the prediction method against wind tunnel measurements and CFD data shows reasonable agreement between the three techniques for a wide number of interaction tones.Additionally a theoretical formulation is derived for expressions for the tonal noise generated by the interaction between the bound potential field of one rotor with the adjacent rotor. The bound potential field produced by the thickness and bound circulation of each blade is determined using a distributed source model. The analytical model is compared with an existing model for a point source and is validated using advanced CFD computations. Results show that the potential field mostly affects the first interaction tone. The addition of the potential field component provides an improvement in the agreement with wind tunnel measurements.Overall this work provides new tools for the rapid assessment of the tonal noise produced by an advance open rotor at various operating conditions, and the analytical result can provide further physical insight into the sources of noise.<br/

A triangulation algorithm from arbitrary shaped multiple planar contours

International audienceConventional triangulation algorithms from planar contours suffer from some limitations. For instance, incorrect results can be obtained when the contours are not convex, or when the contours in two successive slices are very different. In the same way, the presence of multiple contours in a slice leads to ambiguities in defining the appropriate links. The purpose of this paper is to define a general triangulation procedure that provides a solution to these problems. We first describe a simple heuristic triangulation algorithm which is extended to nonconvex contours. It uses an original decomposition of an arbitrary contour into elementary convex subcontours. Then the problem of linking one contour in a slice to several contours in an adjacent slice is examined. To this end, a new and unique interpolated contour is generated between the two slices, and the link is created using the previously defined procedure. Next, a solution to the general case of linking multiple contours in each slice is proposed. Finally, the algorithm is applied to the reconstitution of the external surface of a complex shaped object: a human vertebra

3D quantitative evaluation of the left ventricular motion from MRI data

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Development of an improved core noise prediction method for long-cowl engines

This paper describes the process of developing an improved method to predict the core noise radiated by long-cowl engines under static and flight conditions. The proposed method follows the same approach as the industry standard SAE ARP 876 method in terms of structure and source model, but uses: (1) a new, analytical frequency-dependent directivity accounting for radiation, convection and refraction effects through the jet and (2) a new empirical source spectrum determined using a source breakdown code applied to external phased array data acquired on a Rolls-Royce BR700-type engine.</p