Impedance probe to measure local gas volume fraction and bubble velocity in a bubbly liquid

Abstract

A new quasi-steady method to measure gas permeability of weakly permeable porous media Rev. Sci. Instrum. 83, 015113 (2012) Rheological measurements of large particles in high shear rate flows Phys. Fluids 24, 013302 (2012) High pressure rheometer for in situ formation and characterization of methane hydrates Rev. Sci. Instrum. 83, 015106 (2012) Non-resonant parametric amplification in biomimetic hair flow sensors: Selective gain and tunable filtering Appl. Phys. Lett. 99, 213503 (2011) Effect of plumes on measuring the large scale circulation in turbulent Rayleigh-Bénard convection Phys. Fluids 23, 095110 (2011) Additional information on Rev. Sci. Instrum. We have developed a dual impedance-based probe that can simultaneously measure the bubble velocity and the gas volume fraction in length scales comparable to the bubble diameter. The accurate determination of the profiles is very important for comparisons with existing theories that describe the rheological behavior of bubbly liquids. The gas volume fraction is determined by the residence time of bubble within the measuring volume of the probe. We have found that the details of the bubble-probe interactions must be taken into account to obtain an accurate measure of the gas volume fraction at a point. We are able to predict the apparent nonlinear behavior of the gas volume fraction measurement at large concentrations. The bubble velocity is obtained from the cross correlation of the signals of two closely spaced identical probes. Performance tests and results are shown for bubble velocity and bubble concentration profiles in a gravity driven shear flow of a bubbly liquid.

Shear flow of a suspension of bubbles rising in an inclined channel

“…Measurements of the profiles of bubble velocity, bubble velocity variance and bubble concentration were obtained using a dual impedance probe. Details of the experimental technique using the dual impedance probe can be found in Zenit, Koch & Sangani (2003). In § 4, these measurements are discussed and interpreted.…”

The lift force on a bubble in a sheared suspension in a slightly inclined channel

“…The surface tension of an aqueous solution is very insensitive to the concentration of electrolyte (Weissenborn & Pugh 1996). On the other hand, magnesium sulphate increases the electric conductivity of the fluid phase, allowing electric impedance probes (Zenit, Koch & Sangani 2003) to be used to detect passing bubbles.…”

“…The volume fraction and bubble velocity were measured as a function of the y position, using a dual impedance probe. The impedance probe detects local changes in the electric resistance near the tip of the probe due to the passage of a bubble and registers this event as a peak in an otherwise relatively quiescent signal (Zenit et al 2003). By measuring the fraction of time for which the signal is above a threshold, which can be obtained by calibrating the probe in a vertical channel with known bubble volume fraction, one can obtain the local volume fraction near the tip of the probe.…”

Electrical conductivity of dispersions: from dry foams to dilute suspensions

“…Considerable effort is spent on deducing the next-order terms in both wet [6,7,8,9,10] and dry [11] limits. Considerable effort is also spent on developing experimental apparatus for both wet [12,13,14] and dry [11,15,16] extremes. Unfortunately, there is little understanding of the intermediate regime where both phases occupy significant volume.…”