Spark technique was applied to qualitative velocity profile visualization in hypersonic flows over compression and expansion corners. For comparison, Schlieren measurement and numerical simulation based on the two-dimensional full Navier-Stokes equations were performed. The computational results did not contradict with the Holden criterion. For shock wave visualization, quantitative agreement among the spark, the Schlieren, and the computational results was good. Further, we found that the spark column shapes observed photographically and the computational velocity profiles correlate to each other. The results demonstrate the capability of the technique.
Photographs have been presented for plane submerged water jets influenced by both boundaries of a free and a solid surface. Visualization of the flow and diffusion of contaminants were realized by a solid tracer method using polystyrene particles, and turbulence in the flow direction of the developing jets was measured with a hot-film anemometer. The jet issuing horizontally from a nozzle attaches to the solid surface or to the free surface, and the latter are classified into six flow types. Discussions are given on the flow characteristics and the diffusion of the momentum and the contaminants for each type of the jets. Their features are greatly associated with the direction of the jet deflection to the boundary. The jet attaching to the free surface spreads below the region near the attachment point further than that attaching to the solid surface, and it encourages the diffusion of the contaminants. The results for another flow patterns, which appear on lowering a water level, are also displayed.
An inclined plume, generated by saline water, is visualized with an echo sounder. The output signal is stored as digital data so that the picture of reflection distribution can be reproduced with any intensity scale and size by post-processing. The pictures are compared with the data of salinity and temperature profiles obtained from STD measurement. The location of horizontal streaks in the picture of echo image corresponds to the depth of density jumps although the intensity of streaks does not correspond to the intensity of density jumps. The densimetric interface of the inclined plume can be identified as the lowest streak along the bottom. Richardson number of the plume(Ri) is estimated from the amplitude of stationary wave on the undulations of the bed topography based on an assumption of the local conservation of specific energy. The estimated Ri and the entrainment coefficient(E) calculated from the data of STD measurement show that E decreases rapidly when Ri approaches to 1.0. This fact means that the frequently used relationship of power law does not hold well.