ABSTRACT
Throughout the history of aerodynamics there has been a great deal of interest in development of techniques that can be used to help visualize a given flow phenomenon. The flow was observed and photographed by using silk threads, cigarette smoke, and glowing iron particles. The smoke wind tunnels developed by F. N. M. Brown and his colleagues represent a compromise. Because all smoke is toxic to some degree, an in-draft tunnel that exhausts outside the laboratory is highly desirable. Furthermore, because the best position for the smoke tubes is upstream of the inlet, the distance the smoke travels from injector to test section must be as small as possible to avoid excessive diffusion. The word smoke is used in a very broad sense, and includes a variety of smoke like materials such as vapors, fumes, and mists. The smoke must be generated in a safe manner and must possess the necessary light-scattering qualities so that it can be readily photographed.
