GSV on a Nozzle Spray
An indoor fire-suppression sprinkler spray nozzle was tested using a Global Sizing Velocimetry (GSV) system, with the goal of characterizing the size and velocity of the droplets generated.
The image to the right shows the experimental setup. The camera was positioned to measure the droplets at a point 13 cm downstream of the nozzle. Water was contained in a tank pressurized to 20 psi, and forced through the nozzle exit.
A 200 mJ New Wave laser was used to illuminate the droplets, and a -25 mm cylindrical lens and a 500 mm spherical lens were used to generate the light sheet. A TSI 4 megapixel camera was used to take the images, coupled to a 105 mm Nikon lens. In addition, a 532 nm bandpass filter and two 4x neutral density filters were placed on the camera lens.
The plot shown here includes diameter data from 318 GSV images. It is common in GSV to obtain many images in order to establish a good statistical base of ~1000 samples, i.e. ~1000 droplet diameter measurements.
The peak diameter is near 100 microns.