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A powerful flow visualization based on a laser-sheet and the quantification of the intensity of the lightfrom Mie scattering had been introduced and successfully used to evaluate the statistics and spatialcorrelations of gas distribution injected into a two-dimensional turbulent recirculation airflow, utilizing abackstep configuration. In the experiment the free stream velocity was, U, = 10 m/s and the step heightwas, H = 20 mm. The study focussed on the _fluctuation and the gas distribution in the recirculation zonein order to elucidate the gas-air moving characteristics. The results show that the distribution of injectedgas shows different trends depending on the location of injection. When the specific momentum ofinjection is increased the maximum fluctuation level of the gas concentration decreases. A reduction upto 30 % of the maximum RMS value of luminance intensity _fluctuation can be observed when increasingspecific momentum ratio of injection from 0. 04 to 0.3. Spatial correlations suggested that mixing betweeninjected gas and surrounding air was more rapid and better in case injection in the near reattachmentpoint due to higher turbulence in the region. |
