Air flows steadily through a long straight duct at Mach number

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Waves, acoustics and compressible flow · Waves, acoustics and compressible flow

Signal Speeds in Fluids, Ch Sound in a moving, absorbing fluid: sources, refraction and loss

Problem

M=0.2

, so the flow speed relative to the duct walls is

U=0.2\,c_0

with

c_0=343.2\,\mathrm{m\,s^{-1}}

. A loudspeaker fixed to the duct wall emits a pure tone of frequency

f=500\,\mathrm{Hz}

. ((a)) Find the wavelength of the tone measured downstream of the source. ((b)) Find the wavelength measured upstream of the source. ((c)) Find the ratio of the downstream to the upstream wavelength.

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