A flow visualization around an obstacle by oil film method

Flow patterns around an obstacle settled between walls in a parallel channel were investigated by oil film method which was one of the flow visualization procedures. In the oil film method, visual flow patterns are drawn with a film spread on a body surface. The oil film used in this experiment was a mixture which was composed of silicon oil, pigment and Oleic acid. The composition of the mixture was adjusted until flow patterns could observe at the most clear conditions for each flow velocity. The application range of this method was extended to lower velocity of air flow than the usual value since the composition of the oil film was improved. Six types of obstacles in configuration were chosen for the experiment: one was a vertical cylinder and the others were five kinds of objects simulated spacer-ribs on fuel rod surface in HTTR. Observations were performed to reveal appearances of flow patterns around various obstacles such as a counter flow region in front of the obstacle, a horseshoe vortex around it and a wake flow region in the rear of it. Numerical calculations were also carried out for flow around the obstacle. The experimental results found to be good agreement with those of numerical calculations. (author)