Simultaneous, noninvasive determination of fluid viscosity and density from acoustical resonances.

U‐tube densitometers make fluid density measurements based on eigenfrequency shifts, which depend on the fluids contained within the densitometer. This measurement method is the current standard for density measurements in industrialized settings. However, ruggedized densitometers have several drawbacks. They are expensive, and require diverting fluids into the apparatus to make their measurements. Viscometers, too, are considered invasive, or require diverting fluid into a measurement chamber (the one exception is the “OSCAR” viscometer, which cannot make measurements on flowing systems). In contrast, a simultaneous density/viscosity measurement can be made without diverting fluid from the container or pipe carrying it. The measurement, in which the container (e.g., pipe section) itself becomes the sensor, is based on acoustical frequency resonance shifts and resonance width changes. Such measurements can in principle be made at a standoff from the container, reducing price and requiring no further contact with the fluids. This presentation will address the technique, give the theoretical background for it, and present experimental validation.