Surface Oil-Film Visualization, Tuffs and smoke
A typical surface oil-flow visualization is shown in Figure 4.12 with highlighted streamlines and reference coordinate lines. This technique is used as a qualitative tool to identify topological surface structures on the vane, hub and shroud. The facility is instrumented with an embedded video camera for photo and video recording of the oil-film development. An oil-kerosene mixture with pigment particles is adapted for operating velocity and blade loading by changing proportion of the components to control the evaporation rate and viscosity of the mixture. Tuffs and smoke is commonly used as well to flow visualisation, its shown to the right below on a truck tested in the L2 windtunnel.
Figure 4.12. Surface oil-flow visualization on OGV.