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Experimental investigation of free rotor noise using a simplified rotor configuration

Wednesday, 26 October, 2011 - 16:00
Campus: Brussels Humanities, Sciences & Engineering campus
Michael Bilka
phd defence

An experimental investigation of the sound produced by an open (unducted) axial fan is
made using a simplified rotor blade geometry. The advantage of such a configuration is
to allow the specific targeting of rotor noise sources, while limiting the geometrical
effects of modern fan blade design and ducting.

To achieve this a simplified blade configuration was utilized (previously designed for this
purpose in conjunction with Michigan State University and Valeo Motors) and a new
anechoic wind tunnel for axial flow fan aeroacoustic measurements was designed and
constructed at the von Karman Institute.

Competing sound mechanisms such as turbulence ingestion noise, self noise, etc. can
then investigated and compared to current simplified aeroacoustic models. This
represents a unique step in that most engineering models are based on twodimensional
airfoil theories that are extended to rotation and compared to full fans (too
complex) or what is essentially rotating flat plates (too simple) as the models do not
account for the geometrical complexities (sweep, lean, variable chord, etc.) of modern
fan blades . These experiments will then allow for the assessment/extension of such
models without those complexities, but with still an aerodynamically meaningful fan
blade. Finally, it will also provide a valuable database (and due to its relative simplicity,
possibly a benchmark) of experiments which can be used to validate more advance
methods in aeroacoustics, such as LES and Hybrid methods in computational

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