Temperature dependence of bulk viscosity in water using acoustic spectroscopy

TL;DR

This study uses acoustic spectroscopy to measure how water's bulk viscosity varies with temperature, revealing it is significantly larger than shear viscosity and demonstrating the method's broad applicability.

Contribution

The paper introduces a robust acoustic spectroscopy method to accurately measure the temperature-dependent bulk viscosity of fluids, validated on water over 7 to 50°C.

Findings

Bulk viscosity of water is about three times larger than shear viscosity.

Measured attenuation spectra match theoretical predictions.

Technique can be applied to various fluids for viscosity measurement.

Abstract

Despite its fundamental role in the dynamics of compressible fluids, bulk viscosity has received little experimental attention and there remains a paucity of measured data. Acoustic spectroscopy provides a robust and accurate approach to measuring this parameter. Working from the Navier-Stokes model of a compressible fluid one can show that the bulk viscosity makes a significant and measurable contribution to the frequency-squared acoustic attenuation. Here we employ this methodology to determine the bulk viscosity of Millipore water over a temperature range of 7 to 50 degrees Celsius. The measured attenuation spectra are consistent with the theoretical predictions, while the bulk viscosity of water is found to be approximately three times larger than its shear counterpart, reinforcing its significance in acoustic propagation. Moreover, our results demonstrate that this technique can be readily and generally applied to fluids to accurately determine their temperature dependent bulk viscosities.