CFD solves vibration problem in ducting
An electrical utility company providing base load and peak demand supply to the grid.
During a recent process upgrade of a silencer duct, process engineers reported significant vibrations in the duct walls. It was postulated that the source of the vibration may have been from acoustic baffles within the ducting.
Matrix was commissioned to confirm the source of vibration and aid in redesign of the baffles. A transient Computational Fluid Dynamics (CFD) simulation of the duct and baffles was performed with STAR-CCM+ www.cd-adapco.com (momentum couple finite volume CFD code) and vortex shedding off the trailing edge of the second row of acoustic baffles monitored.
This resulting simulation predicted that the pressure disturbance from the vortex shedding propagated upstream, resulting in flip-flop effect as the flow oscillated between two available paths between the sets of baffles. This CFD predicted transverse pressure frequencies tightly agreed with measurements of the dominant panel vibration modes to within a few percent.
Once the CFD model had been verified against the measured noise frequency, the model was then extended to look at options such as modifying the trailing edge geometry to prevent the vortex shedding.
An added benefit was that Matrix was able to eliminate a more costly modification with the final design, resulting in measurable efficiency improvements in the ducting and baffles.
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