Visualisation of turbulent spots under the influence of adverse pressure gradients

In this paper, a method of using temperature sensitive liquid crystal to visualize the thermal footprints of turbulent spots is described. It is employed to study the nature and development of artificially created turbulent spots in a laminar boundary layer over a heated surface under the influence of adverse pressure gradients in a water flow experiment. This method not only provides qualitative information about the structures and growth of the spot but also contours of heat flux beneath an entire spot as it propagates downstream. Furthermore, the lateral spreading angle and propagation rate of turbulent spots are obtained by analysing the colour images and heat transfer contours. The results are compared with those obtained by other researchers using different experimental methods