Experimental study of steady concentration fields in turbulent wakes

The pollutant transportation process in turbulent wakes is studied experime ntally using planar laser-induced fluorescence (PLIF). The concentration fi elds in the very near wake region behind typical bluff bodies are measured for steady flow. The characteristics of the mean and instantaneous concentr ation fields behind circular and sinusoidal islands and peninsulas are inve stigated. The results indicate that the pollutant distribution is closely r elated with the unsteady vortex shedding in the flow field. Compared with t hat of the circular island, more pollutants enter into the wake generated b y the sinusoidal-shaped island. The time needed for pollutants to accumulat e in or drain out of the wake region after the peninsula before reaching a relatively constant value is longer than that for the islands, regardless o f the island or peninsula shape. The results will facilitate pollutant cont rol behind sea islands and other natural or man-made structures in water. A lso the results provide some fundamental data for checking numerical models .