Internal Report

Measurement and calculation of guide-vane performance in expanding bends for wind-tunnels

Abstract

The design of guide vanes for use in expanding bends was investigated both experimentally and numerically. The primary application in mind is the use of expanding corners in wind-tunnels for the purpose constructing compact circuits with low losses. To investigate the performance of guide vanes in realistic situations expansion ratios between 1 and 5/3 were tested in the experiments. These were carried out in an open wind-tunnel specially built for present purpose. The losses were computed from profiles of total pressure downstream of the corner. The experimental results demonstrated that suitably designed guide vanes give very low losses and retained flow quality even for quite substantial expansion ratios. For wind-tunnel applications expansion ratios around 1.3 seem appropriate. Optimization of the guide vane design was done by solving the steady Euler equations coupled with integral boundary layer equations. A new vane optimized for an expansion ratio of 4/3 gave a (2D) pressure loss coefficient as low as 0.041 for a chord Reynolds number of 200000.