A multi-tip probe for the measurement of the phase velocities in gas-liquid flows

The characterization of gas-liquid flows involves the measurement or prediction of temperature, pressure and velocities, plus some quantities which describe the flow structure. Concerning the latter, the most used is the local void fraction, which in this work is accompanied by the flow complexity, another quantity which evaluates the number of interfaces passing through a point during the sampling interval. The cross-section averaged value of the flow complexity may be put into relation with the liquid velocity. In horizontal ducts, such correlation may assume a very simple potential form or a slightly more complex aspect if the effect of flow development along the duct is included. It can be also determined by detection of the phase density function at different heights on the vertical diameter of the duct cross-section alone. Therefore the liquid velocity and consequently gas velocity (via slip correlations) can be estimated by inline phase density measurements using local impedance probes. The paper presents the preliminary analyses to develop the correlation and the design of a multi-probe sensor to perform the measurements.