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

Document Type : Research Article


1 Assistant professor, Faculty of Engineering, University of Mohaghegh Ardabili

2 Professor of hydraulic structures, Water Engineering Research Center, Tarbiat Modares University


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.


Barbarutsi S., Ganoulis J., and Chu V.H. (1989). Experimental investigation of shallow recirculating flows, J. Hydraul. Eng., 128(10), pp. 891-900.
Davidson, P.A. (2004). Turbulence: An introduction for scientists and engineers, Oxford University Press.
Jirka, G.H. (2001). Large scale flow structures and mixing processes in shallow flows, J. Hydraul. Res., 39(6), pp. 567-574.
Rhoads, B. L. and Sukhodolov, A. N., (2004). Spatial and temporal structure of shear layer turbulence at a stream confluence, Water Resour. Res. 40, W06304, doi: 10.1029/2003WR002811.
Tennekes, H. and Lumley J.L. (1972). A first course in turbulence, MIT Press.
Tukker, J. 1997. Turbulence structures in shallow free-surface mixing layers, PhD Thesis, TU Delft.
Uijtewaal, W. S. J. and Booij, R. (2000). Effects of shallowness on the development of free-surface mixing layers. Phys. Fluids, 12(2), pp. 392-420.
Van Prooijen, B. and Uijttewaal W., (2001). Development of large turbulent structures in shallow mixing layers, Proceeding of the 2001 International Symposium on Environmental Hydraulics, Arizona: 1-6 (CD-Rom).