A phononic crystal-based solution for improved noise and vibration behavior of ram pumps

• A novel phononic crystal (PC)-based drive pipe is designed to suppress vibrations in hydraulic ram pump systems. • Copper–PVC periodic structure forms a 170 Hz band gap, verified by theory and experiment. • Measured wave speed (≈1560 m/s) confirms Bragg-based band gap prediction. • Low Mach number flow (M < 0.006) has negligible impact on band gap behavior. • Small unit cell length changes greatly shift band gap frequency, requiring precise design. Ram pumps, despite serving as off-grid and fossil-free water pumping devices, suffer from significant noise and vibration during operation, adversely impacting both their performance and reliability. The solution proposed in this paper leverages phononic crystals (PCs) concept on the basis of a four-equation fluid–structure interaction (FSI) model to describe and reduce these disturbances. Bloch-Floquet approach has been used to design a PC-based drive pipe consisting of alternating materials, featuring band gaps in the vibrational frequency ranges. The ability of the proposed solution in attenuating noise and vibration and enhancing ram pump performance has been experimentally verified using a hydraulic ram experimental setup. The results show that a drive pipe, constructed with alternating (PVC) and copper pipe sections arranged in 6-unit cells, achieves a 90 % reduction of vibration amplitudes in the pressure signal, leading to a 25 % improvement in the ram pump efficiency compared to the ordinary one operating under identical conditions.