Broadband active control of noise and vibration in a fluid-filled pipeline using an array of non-intrusive structural actuators

Fluid-filled pipelines occur in a wide variety of installations where they are excited by sources such as pumps and compressors through both the structure of the pipe wall and the fluid in the system. These vibrations may propagate downstream and result in unwanted radiated noise from the pipeline or connected structures. Although passive measures are available to control both structure and fluid borne vibration, their operating frequency range is generally limited by the volume and weight constraints that are imposed by the practical installation. Active control methods may overcome these volume and weight constraints and such systems have been investigated for the control of both fluid and structure borne transmission. In particular, previous work has highlighted the ability to control the internal acoustic pressure using non-intrusive fluid-wave actuators. However, although these systems are able to achieve control of the internal acoustic pressure they produce enhancements in the structural vibration and this limits the practical benefit of these systems. This paper investigates the behaviour of a non-intrusive structural controller consisting of an array of piezo stack actuators positioned circumferentially around the pipe and acting on its outside wall. The ability of the system to control the internal, fluid-borne, acoustic pressure and the externally radiated sound pressure is investigated through a series of experiments. These results are then used to highlight the trade-off between controlling the internal and external pressures using the non-intrusive array of structural actuators.