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Porous media treatment is an effective method for passive flow and noise control of a bluff body, such as a cylinder and blunt trailing edge (TE), to minimise vortex shedding processes and aeroacoustic source generation. A prevailing issue in the study of porous media is that the near-wall and internal flow-fields of randomised porous media (such as metal foam or porous polyurethane) can be difficult to analyse experimentally and rely on numerical simulations to elucidate the salient flow physics. To alleviate this problem, a structured porous TE (SPTE) was designed, following a published methodology for designing a structured porous coated cylinder. The SPTE possesses similar porous properties and has a regular lattice structure that allows for independent manipulation of porous properties, such as porosity and permeability. In this study, three types of TE were studied: a solid TE, an SPTE and a melamine foam TE with a randomised porous structure and similar porous properties to the SPTE. To quantify the acoustic emissions and efficacy of each TE, they were attached to an elliptical leading-edge flat plate and tested in an anechoic wind tunnel using a single microphone in the far-field. Experiments were also conducted using time-resolved planar particle image velocimetry in a water flume to quantify the near-wall and wake flow field statistics and how the different porous materials influence their passive flow and noise capability. The experiments revealed that the SPTE showed superior tonal noise reduction, relative to the randomised porous media and solid TEs, primarily due to the attenuation of vertical velocity fluctuations in the wake. Flow passage through the SPTE from the boundary layer into the wake is clearly observed, yet the randomised porous media possesses negligible flow passage. This flow communication through the SPTE modifies the development of the recirculation zone, reverse flow region and the interaction of the shear layers, thereby influencing the vertical velocity fluctuations in the wake and thus radiated far-field pressure.

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Near-Wall and Wake Flow Fields of a Blunt Trailing Edge Appended with Structured and Randomised Porous Media

  • 会议论文

  • 发表日期：

    2025年

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  • Elias J. G. Arcondoulis,
  • Daniele Ragni,
  • Daniele Fiscaletti,
  • Roberto Merino-Martinez

摘要

Porous media treatment is an effective method for passive flow and noise control of a bluff body, such as a cylinder and blunt trailing edge (TE), to minimise vortex shedding processes and aeroacoustic source generation. A prevailing issue in the study of porous media is that the near-wall and internal flow-fields of randomised porous media (such as metal foam or porous polyurethane) can be difficult to analyse experimentally and rely on numerical simulations to elucidate the salient flow physics. To alleviate this problem, a structured porous TE (SPTE) was designed, following a published methodology for designing a structured porous coated cylinder. The SPTE possesses similar porous properties and has a regular lattice structure that allows for independent manipulation of porous properties, such as porosity and permeability. In this study, three types of TE were studied: a solid TE, an SPTE and a melamine foam TE with a randomised porous structure and similar porous properties to the SPTE. To quantify the acoustic emissions and efficacy of each TE, they were attached to an elliptical leading-edge flat plate and tested in an anechoic wind tunnel using a single microphone in the far-field. Experiments were also conducted using time-resolved planar particle image velocimetry in a water flume to quantify the near-wall and wake flow field statistics and how the different porous materials influence their passive flow and noise capability. The experiments revealed that the SPTE showed superior tonal noise reduction, relative to the randomised porous media and solid TEs, primarily due to the attenuation of vertical velocity fluctuations in the wake. Flow passage through the SPTE from the boundary layer into the wake is clearly observed, yet the randomised porous media possesses negligible flow passage. This flow communication through the SPTE modifies the development of the recirculation zone, reverse flow region and the interaction of the shear layers, thereby influencing the vertical velocity fluctuations in the wake and thus radiated far-field pressure.