Partially-filled pipe flows are commonly observed in urban hydraulics, sewers and road crossings. The occurrence of a compression wave in the confined space may result from flash flooding, transient operation or accidental blockage, inducing explosive conditions. In this study, the propagation of a compression wave was studied in a relatively large-size laboratory flume with a semi-circular cross-section. The unsteady flow properties were recorded to understand how the circular cross-sectional shape impacted onto the surging water propagation. Both free-surface and velocity data indicated a marked impact of the compression wave passage, with large instantaneous fluctuations comparable and sometimes larger than observations of compression waves in rectangular channels.

Partially-filled pipe flows are commonly observed in civil, environmental and sanitary engineering. The propagation of a positive surge in a confined space might create explosive conditions. Herein the propagation of a compression wave was investigated physically in a relatively large-size semi-circular channel. The unsteady turbulent characteristics were recorded to understand how the sudden cross sectional shape change impacted onto the transient surge propagation and unsteady flow characteristics.