Mechanics Department Info Faculty and Staff Research Courses Seminars Open Positions MSc Thesis Projects Centers Intranet

# Internal Report

## Evaluation of the flow quality in the MTL wind-tunnel

The flow characteristics of the MTL wind-tunnel at the Department of Mechanics, KTH, have been evaluated 10 years after its completion. The wind-tunnel is of closed circuit type with a $7$ m long test section that has a cross section area of $1.2 \times 0.8$ $\mathrm{m}^2$. The contraction ratio is $9$ and the maximum speed is approximately $70$ m/s. The experiments performed included measurements of total pressure variation, temperature variation, flow angle variation and turbulence intensity variation. The measurements were carried out in the test section over a cross flow measurement area of $0.9 \times 0.5$ $\mathrm{m}^2$ located $0.4$ m downstream the inlet. The temperature variation in time was also measured at the center of the measurement area. The experiments were performed at three different wind-tunnel speeds, 10, 25 and 40 m/s. The present results confirm that the high flow quality of the MTL wind-tunnel. The flow quality measurements carried out soon after the completion of the tunnel are here repeated and extended. For instance, at 25 m/s the streamwise turbulence intensity is less than $0.025\%$ and both the cross flow turbulence intensities are less than $0.035\%$ at the same speed. The total pressure variation is less than $\pm0.06\%$ and the temperature variation is less than $\pm0.05{\;}^\circ\mathrm{C}$.