Ultrasonic Attenuation and Volume Viscosity in Liquid Nitrogen

Abstract

The volume viscosity in liquid nitrogen has been calculated from ultrasonic attenuation measurements at temperatures between 73.6° and 113.8°K with pressures up to 141.5 kg/cm². Measurements of attenuation as a function of pressure were made using single transducer, pulsed systems. The low‐pressure apparatus employed a variable‐path‐length sample chamber while the high‐pressure study was made with a fixed double‐path‐length cell. The measured attenuation depends linearly on the square of the frequency over the range 30–70 Mc/sec. The volume viscosity of liquid nitrogen increases with increasing density and shows the same density dependence as has been reported for liquid argon. The volume viscosity of liquid nitrogen ranges from 1.3 g/cm·sec at a density of 0.650 g/cm³ to 2.4 g/cm·sec at a density of 0.850 g/cm³ and has the same order of magnitude as the shear viscosity. The ratio of volume viscosity to shear viscosity at a temperature of 77.6°K and pressure of 1.67 kg/cm² is 1.2. The results indicate that no internal molecular relaxation processes are involved in liquid nitrogen so that the bulk viscosity is the same as the volume viscosity.