However with regard to the initial drop size, it should be noted that Watson’s axisymmetric model predicts a relatively small viscous sheet thickening effect (important for atomization).
Without measurements it is difficult to verify if the viscous interaction with the deflector in actual sprinklers is also small;
however, this result would be consistent with the short length scales associated with the deflector geometry.
Comparisons between drop size predicted with ‘ideal’ sprinklers and actual sprinklers in Section 3.1 should shed some light on the importance of viscous effects in actual sprinkler geometries.