Modelling Acoustic Sources in Pipework

The internal gas flow within a pipework system can generate large noise levels which may be sufficient to cause vibration and fatigue damage. The sources of such noise can be modelled by means of acoustic oscillations of inflow and outflow from a point location. Single and multiple point locations (monopoles and dipoles) within pipework are analysed to determine the different wave structures they generate. Use is made of frequency domain methods within which the effects of damping can be included by using reflection coefficients which allow some energy to leave the system. In order to model the source strength some data (due to Graf and Ziada) are analysed to determine how the source is linked to the flow within the pipework. Use is again made of frequency domain methods to represent this data. The source is found to contain a mixture of negative and positive damping which depends on the flow rate in a non-linear manner. Throughout this investigation the physical nature of the mechanisms involved is emphasised and the use of frequency domain methods is found to be successful.