Gross-Hardt, E, Amar, A, Stapf, S, Blümich, B, Andreas Pfennig:
Flow dynamics measured and simulated inside a single levitated droplet
Industrial & Engineering Chemistry Research, 2006, 45(1), 416 - 423
The flow dynamics inside a single liquid droplet of toluene levitated by a countercurrent of deuterated water (D2O) is investigated noninvasively and quantitatively by nuclear magnetic resonance (NMR) imaging techniques for the first time and compared with computational fluid-dynamics (CFD) calculations. For this purpose, a unique device is developed meeting the requirements for long period measurements (namely, a permanently stable droplet position and shape) and for measurements on series of droplets (namely, a high reproducibility of generation and position of droplets). The measurement cell of this device is manufactured with low tolerances regarding axial symmetry and positioned vertical and central in the NMR magnet with high precision enabling axially symmetric flow dynamics. The measured flow field shows good agreement with 2D axially symmetric CFD calculations with the finite element (FEM) code SEPRAN. A simple interface model with one free parameter accounts for the rigid cap encountered in the measurements. This free parameter is estimated by matching the velocity fields of the simulation with those determined experimentally.