Sharif Digital Repository

Contraction sections are an integral part of all wind tunnels, whether designed for basic fluid flow research or model testing. The location of the contraction, just upstream of the test section, makes it very important to achieve a high quality contraction design. The effect of a contraction on unsteady velocity variations is significant to increase the mean velocity. Furthermore, contraction has a suitable role on the turbulence reduction in a wind tunnel. The contraction itself further reduces the turbulence in terms of percentage of the wind speed. This is due to the increase of the wind speed by a factor equal to the contraction ratio. In this research, to investigation flow quality in... 

The impact of a method on the turbulence reduction in wind tunnels was evaluated. In this method, by installation of trip strip in the contraction, the unsteady behaviors of flow have controlled, consequently the turbulence intensity and possibility of separations were decreased. Location and diameter of trips were very important in this method. Various sizes of trip strip were installed at different locations in the contraction section of four different wind tunnels to study the most significant aspects of the method. Hot wire anemometry system, 1-D and 2-D probes, were used for turbulence measurement and a new method for direct calibration of a 2-D hot-wire probe was introduced. The new...