Flow-induced pressure pulsations are common phenomena in natural gas pipelines, steam power plants and similar piping systems and occur at discontinuities in the pipeline, generally at a T-junction with a pressure relief line or other closed sidebranch. Such pressure pulsations are undesirable since they may cause pipe vibrations leading to material fatigue and gas explosions, generate excessive noise and disturb flow rate measurements.
It is known that these pulsations are generated by vortex shedding at the branch pipe. The vortex shedding frequency, or Strouhal number, is determined by the relationship: ##EQU1## wherein S is the Strouhal number, fs is the Strouhal centre frequency, d is the diameter of the sidebranch pipe and v is the velocity in the main line. Coincidence between the Strouhal number and the resonant acoustical frequency of the closed sidebranch pipe causes the pressure pulsation to occur.
In instances where such pressure pulsations have occurred, it has been suggested to alter the length of the sidebranch pipe to change its resonant frequency outside the Strouhal eddy shedding frequency range. However, this solution is not universally applicable, and is not practical for a piping system which is to carry gas over a wide range of flow rates.
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