The application of lasers to time-resolved flow visualization

In streak photography of transient flow a very bright, narrow, flat beam of light is required, and this is usually produced by an illuminated slit. This paper shows that it is easily produced with coherent laser light. Even a low-power laser can give a narrower and brighter beam, and hence improved space and time resolution. A framing camera may be produced by scanning the beam with a rotating mirror, and this also would permit the use of a low-power laser for visualization of high-speed turbulent flows. Any of the usual methods of visualization may be used, including holography, interferometry, schlieren or shadow photography. Experimental results are presented which show that the expected good resolution may in fact be obtained in practice.