Acoustic resonance experiments in a reservoir - pipeline - orifice system

Acoustic resonance in liquid-filled pipe systems is an undesirable phenomenon that cannot always be prevented. It causes noise, vibration, fatigue, instability, and it may lead to damage of hydraulic machinery and pipe supports. If possible, resonance should be anticipated in the design process and be part of the hydraulic-transients analysis. This paper describes acoustic resonance tests carried out at Deltares, Delft, The Netherlands, within the framework of the European Hydralab III programme. The test system is a 49 m long pipeline of 206 mm diameter that is discharging water from a 24 m high reservoir through a 240 mm2 orifice to the open atmosphere. The outflow is partly interrupted by a rotating disc which generates flow disturbances at a fixed frequency in the range 1.5 Hz to 100 Hz. In previous studies [1, 2] a similar system was analysed theoretically. Herein experimental data are presented and interpreted. Steady oscillatory behaviour is inferred from pressures measured at four different positions along the pipeline. Heavy pipe vibration during resonance was observed (visually and audibly) and recorded by a displacement transducer.