AIRFLOW pictures comprise the major part of this paper. Before presenting them, the Griswold Smoke Tunnel used for making them is described.
The photographic figures show some typical flow pictures obtained in this tunnel, mostly of conventional devices, some of which give an idea of the sort of investigations that may be profitably conducted therein, visually.
The tunnel is of the non-return-flow type which design is dictated by the need for continuous supply of fresh air when smoke lines are injected into the flow. The test area, which is spanned by the model so as to give two-dimensional flow, has a high narrow rectangular cross-section. A heavy plate glass window is mounted flush with the internal surface in the front face of the tunnel to expose the model to view, together with a field of 24 streamlines.
The powerplant consists of a centrifugal blower belt-driven from an internal-combustion engine, with which combination air speeds up to 80 mph can be attained. Exhaust heat from this engine is utilized to activate the smoke-supply apparatus. Smoke is generated by smoldering rotten wood in a special-type stove.
With this equipment a variety of model changes and modifications can be provided, the principal flow characteristics of which can be explored in a fraction of the time (and thus expense) and, in certain elemental respects, more thoroughly than is normally the case for the less flexible three-dimensional quantitative tests. This tunnel is by no means a substitute for the latter equipment, the author qualifies, but it already has proved to be a useful and convenient piece of supplemental equipment for preliminary and exploratory flow research concerned with aerodynamic problems susceptible to two-dimensional investigation.