Each Bubble Generator must be fitted with appropriate nozzles to match the screen size and shape. Round housings will be covered with a circular area screen and so a round, full cone nozzle will cover the screen and make it uniformly wet. The spiral nozzle is a very good choice since it never gets clogged up and gives a fine, "full cone" droplet pattern. You need to select the liquid flow from the nozzle to match the air flow provided by the fan or blower that you are using and also take care to use a nozzle with the correct angle of spray and place it at the correct distance from the screen. Typically only one nozzle, placed just downstream from the fan and centered in the housing pointing at the screen will do a fine job. Here are 4 sources and some catalog photos of the spiral nozzle:
Other sources people have found: Spiral Nozzles at McMaster-Carr
Other Bubble Generators may have a square outlet to the air or bubble flow. Then the screen will be square in area and a nozzle or group of nozzles that cover this shape of screen should be choosen. These would be the square full cone spray nozzles.