Intermittent two-phase flow study by NMR

Co-circulation of gas and liquid in a pipe can generate, depending on inlet conditions, various kinds of flow patterns. Few investigations have been performed on intermittent two-phase flows (slug flows) using classical techniques (optical probe, hot-wire anemonetry, etc,), because these techniques are difficult to apply in this flow regime. Here we show that nuclear magnetic resonance is a powerful technique to study such flows. The presented results deal with controlled isolated Taylor bubbles. In addition to a classical Pulsed Field Gradient Spin Echo (PFGSE), a magnetic field gradient was applied during the pi /2)(X) radio frequency pulse, which produces a selective irradiation. Thus, cutting up of the flow into slices provides the longitudinal evolution of the liquid fraction and of the velocity probability distribution in the entire region perturbed by the Taylor bubble. The existence of a recirculatory flow under the Taylor bubble is clearly demonstrated. (C) 2001 Academie des sciences / Editions scientifiques; et medicales Elsevier SAS.