Author(s): Daniele Longo; Aggelos Dimakopoulos; Ian Willoughby

Linked Author(s):

Keywords: Swirling flow; Pump intake; CFD modelling

Abstract: Pumping stations are hydraulic structures that are used in many different types of critical infrastructure around the world, including cooling systems for power plants and drainage and wastewater management schemes. Amongst the various hydraulic design tasks performed for pumping stations, the mitigation of swirling flows at the pump intakes is a critical one. Ensuring the absence of swirling flows minimises adverse effects at the pumps, such as stimulation of vibration, cavitation and air entrainment, and ensures good working conditions, allowing pumping equipment to meet the design life requirements. Key performance indicators for ensuring an acceptable hydraulic performance include the variations of the velocity conditions and swirl angles at the pump intakes, and absence of strong surface and subsurface air entraining vortices. According to ANSI/HI-9.8 standards, confirmation of the design against these indicators is recommended to be assessed with physical models. However, with the advance of Computational Fluid Dynamics (CFD) modelling tools the engineering community is interested in the application of these tools as a means to assess hydraulic performance in the context of the ANSI/HI-9.8 performance indicators. The ability to use CFD modelling in this way will allow increased confidence in the design process leading to reduce capital and operational costs. Recent studies have been performed in this direction (Torbaty 2019), but there are still open questions regarding the applicability of CFD modelling and assessment of the hydraulic design and performance against the ANSI/9.8-HI performance indicators described above. In this work, we attempt to address some of the key questions by re-visiting past experiments of pumping stations performed in HR Wallingford’s laboratory and repeating tests using CFD simulations with OpenFOAM. New workflows and analysis methods are proposed to assess the velocity profiles and swirl angles at the intakes and the relative strength of surface and subsurface vortices. Results show that the CFD model results can provide good agreement with experimental data relating to the variation of velocity at the pump suctions, with the CFD model output showing a tendency to slightly overestimate the velocity profile variation. CFD output of swirl angles show a good agreement with experimental trends as and overall indicator of performance, whilst some differences where observed at individual pumps. The methodology proposed to assess CFD model results with respect to the classification of surface and subsurface vortex strength presents a very good correlation with laboratory observations. In overall terms, a good correlation between physical and CFD model results is achieved for assessing hydraulic performance of pump intakes against swirling flow, in the context of ANSI/HI-9.8 standards. The uncertainties of the methodology are also captured and further discussed and evaluated.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022866

Year: 2022