SIMULATING WATER-DROP MOVEMENT FROM NONCIRCULAR SPRINKLER NOZZLES

The conventional approach for determining drag coefficient in the ballistic theory fits well for simulating water-drop movement emitted from circular sprinkler nozzles. This approach was checked for square and double-rectangular nozzles. The conventional approach does not work. Therefore the concept of an ''apparent drag coefficient C-d'' was introduced, and a new approach for determining C-d was developed. It was verified that the spray distance for a specified droplet diameter calculated by the new approach fitted the observed one very well. The effect of droplet diameter; nozzle-shape, nozzle-size, and discharge coefficient; and pressure on C-d was analyzed, and showed that C-d is very sensitive to droplet diameter and nozzle-shape coefficient. The new approach was applied to investigate the influence of a sprinkler's trajectory angle on spray distance, and showed that both circular and noncircular nozzles reached their largest spray distances when the trajectory angle was around 37 degrees. The effect of nozzle shape on the direction of droplet terminal velocity was also investigated.