Experimental Investigation of Roughness Effects on the Wake of S823 Airfoil at Different Speeds

In this research the effect of roughness on airfoil sections with one dimensions hot-wire anemometer has been studied. The factors of oscillating and the average time of flow velocity was measured for two positions. Soft and rough surfaces in 5 and 10 m/s speed, also changes in the drag coefficient was obtained and examined in two modes. For measuring the parameters the sequence method (experimental) for calculating the speed component measurements have been performed without dimension at x/c=0.01, 0.5, 1, 2 and 3 (c means chord length and x means distance from the back of airfoil) was used. According to the graphs and results of experiments it is observed that with increasing distance from the longitudinal direction the width of the trail increased more surface will affect. Also moving away from blade in the longitudinal direction makes minimum speed peaks spread eventually it will go away but in case of a rough surface width of the trail increase and to achieve free-stream velocity we need more distance from blade.