Ethanol at has

PHYSICS · Subjective · Fermi University Physics · Oscillations, Waves & Acoustics · Fluids & Continuum Physics · Acoustics of fluids: generation, propagation and attenuation

Fluid Dynamics, Ch The stress tensor completed: constitutive law and fluid properties

Problem

Ethanol at 20∘C20^{\circ}\mathrm{C} has ρ=789 kg m−3\rho = 789\,\mathrm{kg\,m^{-3}}, speed of sound c=1144 m s−1c = 1144\,\mathrm{m\,s^{-1}} and shear viscosity μ=1.20×10−3 Pa s\mu = 1.20\times10^{-3}\,\mathrm{Pa\,s}. The classical absorption coefficient of a sound wave of frequency ff, defined so that the pressure amplitude falls as e−αxe^{-\alpha x}, is α=ω22ρc3(43μ+μb),ω=2πf,\alpha = \frac{\omega^2}{2\rho c^3}\left(\tfrac43\mu + \mu_b\right), \qquad \omega = 2\pi f, where μb\mu_b is the bulk viscosity. An ultrasonic absorption measurement on ethanol gives α/f2=6.0×10−14 s2 m−1\alpha/f^2 = 6.0\times10^{-14}\,\mathrm{s^2\,m^{-1}}. Find μb\mu_b for ethanol.

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