Concentration Measurement in Bubbly Liquids - A Matter of Times

Leaky Lamb waves in an acoustic cavity can be utilized for the measurement of temperature, density and sound velocity of an enclosed liquid. If the sensitivity of these variables to a change of predefined components in a liquid mixture is high enough, an online concentration measurement can be utilized as well. Gas bubbles can influence the measurable times-of-flight which can be disadvantageous for the concentration measurement. This paper will show how simultaneous group and phase velocity measurements can be used to calculate the sound velocity and the concentration in pure liquids, even if gas bubbles are interspersed.