Fluid mechanics of regurgitant jets and calculation of the effective regurgitant orifice in free or complex configurations

The velocity fields of turbulent jets can be described using a single formu la which includes two empirical constants: k(core) determining the length o f the central core and k(turb) the jet widening. Flow models simulating jet adhesion, confinement and noncircular orifices were studied using laser Do ppler anemometer and the modifications of the constants were derived from s eries of velocity profiles. In circular foe jets, k(core) was found equal t o 4.1 with a variability of 1.4%. In complex configurations, its variabilit y was equal to 15.2%. For k(turb), the value for free circular jets was of 45.2 with a variability of 6.0% and this variability in complex configurati ons was significantly higher (30.1%, p = 0.025). The correlation between th e actual orifice size and the jet extension was poor (r = 0.52). However. t he almost constant value of k(core) allowed to define a new algorithm calcu lating the regurgitant orifice diameter with the use of outlines of the jet image (r = 0.89). In conclusion, the fluid mechanics of regurgitant jets i s modified in complex configurations but, due to the relative independency of the central core, velocity fields could be used to evaluate the dimensio ns of the effective regurgitant orifice. (C) 2000 Elsevier Science Ltd. All rights reserved.