Corrections of gradiomanometer data for volume fractions in two-phase flows

For typical applications of the gradiomanometer in laboratory two-phase flo ws, we analyse major contributions to the measured differential pressure. A pplication for estimation of the fluid-phase volume fraction is valid only when terms representing friction and differential momentum flux (accelerati on) are negligible or can be corrected for. The importance of friction is c ommonly recognized, but that of acceleration in developing Rows is less so. Order-of-magnitude estimates of friction and acceleration are given for ty pical cases of (i) air/water and (ii) kerosene/water two-phase flows. We po int out that the acceleration term could be significant in developing liqui d/liquid flows of weak density contrast. For the liquid/liquid case, it is therefore important that measurements be made in a fully developed region o f the flow. Results for several multi-phase flows are compared with data fr om local optical fibre probes in a series of companion articles.