Turbulence Measurement in a Free Jet by Spark Tracing Method with Color DP Matching

Although the spark tracing method is known as one of the most classical techniques of flow visualization, the measurement by this technique has been limited to a qualitative observation or to one-dimensional velocity measurement. Recently, the authors of this study have been succeeded in measuring the two- or three-dimensional velocity field by applying the DP (dynamic programming) matching technique, which has commonly been used in the voice recognition, to the images obtained by the spark tracing method with the aid of one or two high speed cameras. Presently, the distributions of the mean velocities, rms velocity fluctuations and the Reynolds stresses in an axisymmetric free jet have been compared with those of the previous study. In order to increase the accuracy of this technique, the powder of aluminum oxide, which shows the radiant trails while they are burned by sparks, has been introduced to the flow.