Nuclear Magnetic Resonance: a New Tool for the Validation of Multiphase Multidimensional Cfd Codes

Turbulent transport models and data in bubbly flows are briefly reviewed since they play an important role in the modeling of boiling flows in forced convection. Shortcomings of earlier measurements of the eddy diffusivity by NMR (Lemonnier & Leblond, 2007b) are analyzed and a new procedure is presented which is now consistent with the procedure of Gatenby & Gore (1994) developed for single-phase turbulent flow characterization. The new estimate agrees with those obtained by Serizawa et al. (1975b) with a thermal method and with the model of Sato & Sadatomi (1981). This procedure also provides the liquid velocity fluctuation RMS and the Lagrangian correlation time of velocity fluctuations. In addition, the same NMR technique provides also the area-averaged liquid velocity and void fraction. Bubbly flow data up to transition to slug flow are provided which also agree with exiting drift-flux models (Ishii & Hibiki, 2006). It is finally discussed how the NMR method can be extended to local measurements and may provide a fully non intrusive diagnostic in two-phase flows and which is not limited to bubbly flow.