Optimal distribution of porous media to reduce trailing edge noise

Schulze, J.; Sesterhenn, Jörn

doi:10.1016/j.compfluid.2011.12.022

Cited by 29 publications

(21 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It was found that the porous surface can reduce the far-field noise by up to 13 dB at the fundamental Strouhal peak and this was shown to be due to the weakening of the surface pressure fluctuations near the trailing-edge and also breaking of the wall pressure fluctuations spatial correlation. In a later study, Schulze & Sesterhenn (2013) investigated the use of porous materials for trailing-edge noise control and developed a methodology to maximise the noise reduction by optimizing the porous material. Koh et al (2014) performed numerical simulations based on LES and acoustic perturbation equations (APE) on the possibility of bluntness noise reduction and found that the use of porous trailing-edges can reduce the sound pressure level at the fundamental vortex shedding frequency by 10 dB and the overall sound pressure level in the range of 3-8 dB.…”

Section: Introductionmentioning

confidence: 99%

Trailing-edge flow and noise control using porous treatments

2018

View full text Add to dashboard Cite

This paper is concerned with the application of porous treatments as a means of flow and aerodynamic noise reduction. An extensive experimental investigation is undertaken to study the effects of flow interaction with porous media, in particular in the context of the manipulation of flow over blunt trailing edges and attenuation of vortex shedding. Comprehensive boundary layer and wake measurements have been carried out for a long flat plate with solid and porous blunt trailing edges. Unsteady velocity and surface pressure measurements have also been performed to gain an in-depth understanding of the changes to the energy–frequency content and coherence of the boundary layer and wake structures as a result of the flow interaction with a porous treatment. Results have shown that permeable treatments can effectively delay the vortex shedding and stabilize the flow over the blunt edge via mechanisms involving flow penetration into the porous medium and discharge into the near-wake region. It has also been shown that the porous treatment can effectively destroy the spanwise coherence of the boundary layer structures and suppress the velocity and pressure coherence, particularly at the vortex shedding frequency. The flow–porous scrubbing and its effects on the near-wall and large coherent structures have also been studied. The emergence of a quasi-periodic recirculating flow field inside highly permeable surface treatments has also been investigated. Finally, the paper has identified several important mechanisms concerning the application of porous treatments for aerodynamic and aeroacoustic purposes, which can help more effective and tailored designs for specific applications.

show abstract

Section: Introductionmentioning

confidence: 99%

Trailing-edge flow and noise control using porous treatments

2018

View full text Add to dashboard Cite

show abstract

“…Three predominant approaches exist for airframe noise minimization -via shape optimizations, 4, 18, 21 injection of gas mixtures, 13,14 and modification of the trailing edge with porous materials. 2,22 In this work, we adopt the last approach.…”

Section: Introductionmentioning

confidence: 99%

On the Adjoint-based Control of Trailing-Edge Turbulence and Noise Minimization via Porous Material

Zhou

Gauger

Koh

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

View full text Add to dashboard Cite

In this paper, we present a discrete adjoint-based optimization framework to obtain the optimal distribution of the porous material over the trailing edge of a 3-D flat plate. The near-body strength of the noise source generated by the unsteady turbulent flow field is computed using a high-fidelity large-eddy simulation (LES). The acoustic signal thus generated is then propagated to the far-field using the acoustic perturbation equations (APE). The design gradients are computed using the forward and reverse modes of algorithmic differentiation (AD). The increase of memory requirement in the reverse mode AD is alleviated by checkpointing. By optimally controlling the material porosity and permeability, it is possible to minimize the turbulence intensity responsible for noise generation at the trailing edge and thus significantly reduce the radiated noise. The optimal porous trailing-edge design achieves a noise reduction of up to 18dB.

show abstract

“…Permeable trailing edges have been investigated in several recent studies [16,22,23,24,25,26,27,28,29]. In one of their first studies on airfoils, Sarradj and Geyer [23] constructed completely porous (polymer, glass or metallic) airfoils of different flow resistivity, and tested their aerodynamic and aeroacoustics performances.…”

Section: Introductionmentioning

confidence: 99%

“…They attributed the low-frequency noise abatement to the role of the porous insert in changing the ratio of the wall-normal to the wall-parallel velocity components. There have also been a few analytical and numerical studies on the optimal distribution of rigid porous media using a discrete adjoint-based optimization framework [26,27].…”

Section: Introductionmentioning

confidence: 99%

Role of Polymeric Coating on Metallic Foams to Control the Aeroacoustic Noise Reduction of Airfoils with Permeable Trailing Edges

et al. 2019

View full text Add to dashboard Cite

Studies on porous trailing edges, manufactured with open-cell Ni-Cr-Al foams with sub-millimeter pore sizes, have shown encouraging results for the mitigation of turbulent boundary-layer trailing-edge noise. However, the achieved noise mitigation is typically dependent upon the pore geometry, which is fixed after manufacturing. In this study, a step to control the aeroacoustics effect of such porous trailing edges is taken, by applying a polymeric coating onto the internal foam structure. Using this method, the internal topology of the foam is maintained, but its permeability is significantly affected. This study opens a new possibility of aeroacoustic control, since the polymeric coatings are temperature responsive, and their thickness can be controlled inside the foam. Porous metallic foams with pore sizes of 580, 800, and 1200 μm are (internally) spray-coated with an elastomeric coating. The uncoated and coated foams are characterized in terms of reduced porosity, average coating thickness and air-flow resistance. Subsequently, the coated and uncoated foams are employed to construct tapered inserts installed at the trailing edge of an NACA 0018 airfoil. The noise mitigation performances of the coated metal foams are compared to those of uncoated metal foams with either similar pore size or permeability value, and both are compared to the solid trailing edge reference case. Results show that that the permeability of the foam can be easily altered by the application of an internal coating on the metallic foams. The noise reduction characteristics of the coated foams are similar to equivalent ones with metallic materials, provided that the coating material is rigid enough not to plastically deform under flow conditions.

show abstract

Optimal distribution of porous media to reduce trailing edge noise

Cited by 29 publications

References 25 publications

Trailing-edge flow and noise control using porous treatments

Trailing-edge flow and noise control using porous treatments

On the Adjoint-based Control of Trailing-Edge Turbulence and Noise Minimization via Porous Material

Role of Polymeric Coating on Metallic Foams to Control the Aeroacoustic Noise Reduction of Airfoils with Permeable Trailing Edges

Contact Info

Product

Resources

About