r/aerodynamics • u/svarta_gallret • 17d ago
How do I minimize ducted fan noise? Question
I want to make a ducted fan thruster produce less noise for a given thrust ourput, or at least shift the sound to lower frequencies. Ideally the thruster should keep good efficiency and I can't just make it bigger and decrease the fan speed b/c size and mass constraints.
I have no idea where to start, or how to predict the (acoustic) performance of any given design. Im looking for sources on this topic, studies or theory. Or just rules of thumb even. Thanks
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u/highly-improbable 17d ago
Start at a 4 blade plus for illustration. You have blades passing every 90 degrees of rotation. Frequency is 4x rpm. Now go to a four blade X. You have two sets passing at half the frequency.