A Corrosion-to-CFD Framework for Quantifying Surface-Roughness Effects on a 316L Stainless-Steel Centrifugal Pump in Saline Service

Abstract Corrosion roughening of wetted pump surfaces may shift the near-wall shear, turbulence, secondary flow, and hydraulic-loss balances in a centrifugal pump. The traceability of the temporal evolution of the corrosion state to a level of a pump CFD is proven to be elusive for saline service centrifugal pumps. In one previous experimental case, a pump built of 316L SS was exposed for 200 h to 30-ppt synthetic seawater, exhibiting a development of the electrical-input pump efficiency, flow rate, and head, respectively from 70.6, to 58.0, 1.50, to 1.38, and 12.0, to 10.7 m. Arithmetic surface roughness, Ra, in turn, developed from 0.8, to 3.4, and the RMS vibration from 0.20, to 0.75 mm/s [1]. Applying the current framework, one treats these Ra growths as exposure-indexed surface-condition descriptors instead of direct measurements of every wetted pump wall. The framework seeks a reproducible corrosion-to-CFD pathway through five exposure-indexed states, S0-S4. The modeling safeguard differentiates between the acquired values of Ra from the corresponding values of equivalent sand-grain roughness, ks, as ks = Ra, with as an uncertain, pump-specific factor as opposed to a universal constant. The proposed CFD modeling method includes three-dimensional, incompressible RANS with SST k-2 and k- 2 turbulence models, rotating/stationary interfaces, mesh- and time-step verification, multi-point characteristic-curve generation, roughness transfer sensitivity testing, and local roughness regime evaluations. The key endpoint is the head loss, which future CFD simulations can attribute to roughness alone with, thus enabling an estimation of the roughness-induced head loss percentage of the 1.30-m head decline. The residual loss will be assigned to other degradation mechanisms, e.g., clearance or wear ring gaps, leakage, pitting, geometry distortion, and unbalanced impeller. No solver-dependent CFD results are included, as the original pump CAD geometry and CFD were not available. The paper is therefore formulated as a methodology.