Abstract
In this paper, downs dyed in fluorescent dyes and chopped fine are used as the tracer of air in order to visualize stream lines of the air current generated by rotating a propeller without movement.
Lighting is made by using fluorescent lamps with black light which radiates only ultraviolet rays. The propeller is put between lights which are situated in the upper and lower sides of that.
As the result of this experiment, comparatively clear stream lines are obtained, though the thickness of lines is not uniform since it is difficult to make equal the size of fine downs.
