A pipe of internal diameter 244mm, mounted in a 22m long titling flume, was used for all the experiments. For each depth of water the boundary shear stress was measured using a Preston tube of internal diameter 4.8mm. The Preston tube readings were converted to shear stresses by use of Patel's calibration. Ancillary equations are presented giving the correlation between the geometric parameters and the mean and maximum boundary shear stresses.
Attention is also focused on the effect of the hydraulic parameters on the resistance to flow.
The velocity data have been used to produce isovels, from which secondary flow patterns have been inferred and the influence of the side wall on the flow has been examined. The use of the side wall correction procedure has been verified for the current cross sectional shape. The cross sectional shape of the duct was similar to that of the open channel. For each cross sectional shape the boundary shear stresses and point velocities were measured using the Preston and Pitot tube techniques described earlier. In order to fully explore the limits of the wind tunnel, pressure gradient versus discharge curves have been obtained.