By Ron DiGiacomo
Two phase flow is notoriously problematic for most flow technologies. Assume, for instance, 3 % gas by volume entrained in a liquid stream. A velocity meter (e.g. mag, vortex, turbine, ultrasonic, etc.) calculates volume flow by multiplying measured velocity by the free cross sectional area of the meter body (or pipe in the case of non-intrusive, clamp on ultrasonic meters). Even with a fully developed flow profile with relatively high Reynolds Number coupled with theoretically zero velocity error, the desired liquid measurement would be overstated by the amount of “gas void fraction” (GVF), in this case resulting in just over 3% error.