Hydrodynamics of the Mixing Layer Bounding a Separation Zone Using SPIV, Part2: Turbulent Characteristics, Temporal and Spatial Structures

In this paper the measurement of flow pattern along the mixing layer bounding a separation zone using SPIV is peresented. Furthermore, spatial characteristics of the mixing layer have been visualized using uranine dye injection and UV light method. Results of the measurements showed that the maximum turbulent kinetic energy and Reynolds stress occur where the mixing layer characteristics changes.Immediately downstream of the side obstacle the power spectral density of the turbulent fluctuations agrees well with -5/3 slope which is indicative of the 3D turbulent flow. By going downstream, the turbulent energy of the low frequency fluctuations decreases by -3 slopes. This shows that 2D flow structures are dominant. At the reattachment zone, the energy distribution for most of the frequencies decreases by -5/3 slope again. In this part, the turbulent flow generated by the bed friction is responsible for three dimensionality of the turbulent flow. Interaction of two separation zones changes characteristics of the temporal flow structures inside the mixing layer.