On the Applicability of Oil and Dye Technique During the Design Phase and Operation of Experimental Rigs

In this paper, an oil and dye flow visualization technique applied in two different cases of experimental testing is described, namely a single fan in crossflow and the wake of a compressor cascade. In both cases, the mixture of paint was prepared using a highly volatile light mineral or heavy machine oil together with very fine pigments of titanium dioxide (TiO2) or fluorescein sodium in various colors. After the preparation of the mixture, a homogeneous thin film was applied onto the whole investigated surface by painting with a soft brush. The air stream which flows over the surface of the plate modifies the concentration and the homogeneity of the oil film according to the flow conditions very close to the wall. The film was dried by the airflow and photographed for further consideration and field observation. A number of successful as well as unsuccessful flow visualization experiments are presented hereafter. The objective of this work is to provide further information and some general guidelines about mixture concentration at lowand high-speed incompressible flows and to discuss the applicability of this method of visualization technique in complex turbomachinery flows.