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CRUNCH CFD contains an acoustics module for analyzing far-field noise. This module uses the Ffowc Williams-Hawkings (FW-H) formulation for far-field noise propagation. Flow solution is stored on Acoustics Data Surfaces (ADS) during an unsteady calculation. Far-field noise is computed as a postprocessing step.

The CRUNCH CFD framework was used to help our customer, a major pump manufacturer, track down the source of noise from a high-energy, two-stage 19 MW seawater injection pump. Pump operators in the field reported a strong tonal noise at blade passage frequency. The objective of this simulation was to corroborate and understand the source of an experimentally observed tone through acoustic analyses of both single- and two-phase unsteady RANS CFD solutions. Calculations were performed using CRUNCH’s incompressible solver and far-field noise module.

Result from our analyses isolated the pump tonal noise to the interaction of blades traversing through distorted flow from suction inlet bay. While the impeller blade was optimized to reduced cavitation, the lack of broad band cavitation noise made the tonal noise more prominent.

pump suction inlet bay showing noise
Pump suction inlet bay and impeller. Noise level calculated at observer ring in suction inlet.
SPL graph showing noise directivity
Polar directivity in SPL (dB). Calculated noise level shows directivity of noise for each frequency.
SPL diagram of FW-H Surface
Integrated SPL of FW-H Surface over all frequencies.
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