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Laser geometry detection in the Porsche wind tunnel – Base for 3D beamforming and deformation measurements

2018; Multidisciplinary Digital Publishing Institute; Linguagem: Inglês

10.1007/978-3-658-21194-3_71

2198-7440

Jörg Ocker, Lawrence M. Paul,

Flow Measurement and Analysis

Especially in the early stages of the automotive development process, a quick and reliable rating of aero-acoustic sound sources is important to fulfil the challenging requirements. For the localization and a detailed investigation of these aero-acoustic sources a complex system, consisting of three microphone arrays (acoustic cameras) has been established in the Porsche wind tunnel [1][2]. By the system basically 2D source maps are calculated and overlaid with a camera image for each array referring to a virtual focus plane in a certain distance. For complex source situations and in case of highly 3D-structured surfaces, however, the missing "depth information" can lead to misinterpretations. With 3D Beamforming, it is possible to calculate and display the acoustic source map using the correct distances on the entire surface of the measurement object and the merged acoustic information of all three arrays [3]. The basis is a 3D model of the measurement object whose position and orientation to the coordinate system of the microphone array must be known. Above all, at higher car speeds, the forces resulting from the vehicle flow can lead to considerable component deformations (for example door out-boarding) and thus to aerodynamic and acoustic issues. In order to evaluate the correlations and develop corresponding measures, it is necessary to measure and analyze the deformations under wind load exactly. The state-of-the-art 3D laser scan system installed in the Porsche wind tunnel allows the determination of the geometry models required for 3D beamforming, the vehicle position relative to the microphone array and the deformations of planar components. For the deformation measurements, a much higher accuracy than the absolute single point measurement accuracy of the 3D scanners used is achieved using a special statistical evaluation method.