Flow visualization techniques in steady and unsteady flows.

Abstract

Flow Visualization in gas dynamics gives clear idea about variation of pressure and density variation and type of flow developed in the test section. It covers a broad spectrum instead of measurement of parameter at a point. The flow may be steady or unsteady, the techniques for taking photograph also differ.Experiments including flow visualization were performed on three devices i.e. Air Ventilator, Subsonic Closed Cycle Wind Tunnel and a Shock Tube. In the case of Air Ventilator a smoke tunnel is used to provide facilities for visual investigations of air flow phenomenon occuring in the study of aerodynamics. The tunnel is a two dimensional, condensed version of large smoke tunnel. In its operation, smoke filaments pass over the different test models to provide the effects of Air Stream behaviour. It is a fixed unit and is designed so that the test models can be changed rapidly with the minimum effort. The photographs of visual observations are taken for permanent record. The paper presents the construction of smoke techniques and interpretation of photographs taken with different aerofoils and different angle of attack. The experiments on closed cycle Wind Tunnel give the set up for experimentation and Schlieren Photography. The experiments were conducted to find suitable Wind Turbine Rotors.Flow being unsteady in the Shock Tube the experimentation in addition to using pressure transducers, thin platinum resistance thermometers, in corporates short duration light source for Schlieren photographs. Storage Osciloscope is used for recording pressure and temperature traces.All the three rigs are locally fabricated. The visual phenomenon covers subsonic to supersonic flow. The paper also presents the design and description of the instrumentation used.