Anomaly of gas drag force on liquid droplets in a turbulent two-phase flow produced by a mechanical jet sprayer at intermediate Reynolds numbers.

Hydrodynamic properties of a turbulent two-phase flow (water droplets in the air) produced by a mechanical jet sprayer were studied experimentally and the drag force on the droplets was found to be anomalously weak; the drag coefficient is four to seven times smaller than predicted by standard expressions. Several hypotheses are suggested in this article and discussed in an attempt to explain the phenomenon. A two-dimensional model of the flow with the drag anomaly is proposed, which provides excellent agreement between the numerical and experimental results. Taking the drag anomaly into account allows an explanation of a number of features of the two-phase flow that are hard to explain otherwise, in particular, the fact that only about one-half of the initial water jet momentum was transferred to the gas during the experiment. [ABSTRACT FROM AUTHOR]