Influence of surface roughness on pressure fluctuations and flow characteristics in a centrifugal pump

Unsteady pressure fluctuations in centrifugal pumps can cause vibration and noise, jeopardizing operational stability. While many studies have focused on design optimization to mitigate these fluctuations, the influence of surface roughness is often overlooked. This paper investigates the effect of impeller surface roughness on pressure fluctuations within a centrifugal pump. Numerical simulations using Unsteady Reynolds-averaged Navier–Stokes equations with the renormalization group k–ε turbulence model were conducted for four roughness values (Ra = 0, 0.1, 1, and 10 μm) using the CFX solver. The numerical model was validated against experimental data for pump energy characteristics. Time-domain, frequency-domain, and energy transfer analyses were performed using root mean square analysis, Fast Fourier Transform, and Continuous Wavelet Transform. Results at the rated flow rate show that increased surface roughness reduces pressure fluctuation intensity in both impeller and volute regions, with maximum reductions of 7.97% and 5.45%, respectively. Frequency analysis reveals blade passing frequency dominance in the volute, while rotational frequency and its harmonics dominate in the impeller. The amplitudes of these frequencies decrease with increased roughness, with significant reductions of 13.84% and 36.86% observed at points V1 and PS5 when Ra = 10 μm. The mechanism involves surface roughness increasing the width of the high TKE region near the blade leading edge (maximum increase 14.59% on the suction side at a certain location), enhancing turbulence eddy dissipation near the impeller outlet. This accelerates energy dissipation of jet-wake vortex structures before they impinge on the volute wall, weakening rotor–stator interaction and suppressing pressure fluctuations. This study provides insight for pump manufacturing and operational analysis.