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 formula which includes two empirical constants: kcore determining the length of the central core and kturb the jet widening. Flow models simulating jet adhesion, confinement and noncircular orifices were studied using laser Doppler anemometer and the modifications of the constants were derived from series of velocity profiles. In circular free jets, kcore was found equal to 4.1 with a variability of 1.4%. In complex configurations, its variability was equal to 15.2%. For kturb, the value for free circular jets was of 45.2 with a variability of 6.0% and this variability in complex configurations was significantly higher (30.1%, p=0.025). The correlation between the actual orifice size and the jet extension was poor (r=0.52). However, the almost constant value of kcore allowed to define a new algorithm calculating the regurgitant orifice diameter with the use of outlines of the jet image (r=0.89). In conclusion, the fluid mechanics of regurgitant jets is modified in complex configurations but, due to the relative independency of the central core, velocity fields could be used to evaluate the dimensions of the effective regurgitant orifice.