IMPROVED WIDE-FIELD SHADOWGRAPH SET-UP FOR ROTOR WAKE VISUALIZATION

The development of an improved wide-field shadowgraph set-up for rotor wake visualization is described. The improved system makes use of one or more beam splitters, and provides several significant advantages over previously used wide-field shadowgraph set-ups. The primary advantage is that the technique can be used to effectively collocate the point light source and the recording camera on the optical axis. This eliminates various optical deficiencies of previous systems, such as ghost and/or blurred images, contrast gradients, and reduced reflected light intensity at the camera optics. A secondary advantage is that the system can be arranged to permit simultaneous viewing by two separate cameras, such as a still and a video. Typical results are shown, which demonstrate the higher quality of rotor wake shadowgraphs possible with the improved set-up.