Revisiting frequency domain analysis method for water hammer effects on pipeline systems

This paper revisits frequency domain analysis method for water hammer study in a hydraulic system. Detailed investigation of the effect of the flow parameters is conducted. Weaknesses on previous research works were pointed out. A brief presentation of the frequency response function determined from motions equations of transient water flow is firstly presented. A special emphasis was devoted to the effect of frictional flow on resonance pulsations. It was obtained that, unlike previous findings, resonance frequencies in a frictional flow are decayed from odd harmonics. This decay is more or less significant depending on the friction coefficient. The observations related to various effects are also illustrated through a set of test cases that were numerically analyzed. Additionally relative uncertainties highlighting the frictional flow effect on the accuracy of resonant pulsations detection are evaluated.