scholarly journals An alternative permeable topology design space for trailing-edge noise attenuation

2021 ◽  
pp. 1475472X2110032
Author(s):  
Salil Luesutthiviboon ◽  
Daniele Ragni ◽  
Francesco Avallone ◽  
Mirjam Snellen
Keyword(s):  
Drag Coefficient ◽  
Porous Metal ◽  
Metal Foams ◽  
Topology Design ◽  
Low Flow ◽  
Noise Attenuation ◽  
Form Drag ◽  
High Form ◽  
3D Printed ◽  
Flow Resistivity

This study focuses upon a new permeable topology design concept as an alternative to porous metal foams, for turbulent boundary layer trailing-edge (TBL-TE) noise attenuation. The present permeable topology has unconventional characteristics with respect to the metal foams: a combination of low flow resistivity r and high form drag coefficient C. The unconventional characteristics are realized by a Kevlar-covered 3D-printed perforated structure. An experimental study featuring a NACA 0018 airfoil model with a Kevlar-covered 3D-printed TE insert at chord-based Reynolds numbers up to [Formula: see text] is carried out. The airfoil with this TE insert gives a broadband TBL-TE noise reduction up to approximately 5 dB, compared to a solid TE. This reduction varies only slightly with airfoil loading (lower than 1 dB variation), in contrast to the porous metal foams (up to 3 dB variation). When comparing the variation of noise attenuation given by all the permeable materials considered, the variation is found to decrease with the increasing C. This is because C specifies the permeable material's ability to withstand the increasing pressure difference, which causes cross flow that might interfere with the noise attenuation mechanism. Additionally, the drag coefficients as well as the roughness noise of the airfoil equipped with the present TE insert are also significantly lower than those of the metal-foam TE, and are mostly negligible compared to the fully solid airfoil. Based on the findings, design guidelines for permeable TE are proposed: the permeable material shall have a combination of a low flow resistivity and a high form drag coefficient as well as a negligible surface roughness.

scholarly journals Experimental and numerical analysis of compression behaviour of 3D printed metal foams

2020 ◽  
Vol 1706 ◽  
pp. 012213
Author(s):  
R Ramesh ◽  
A S Prasanth ◽  
R Krishna ◽  
K KoushikSundaram ◽  
R Arul MozhiSelvan ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Metal Foams ◽  
Compression Behaviour ◽  
3D Printed

Modelling and Simulation of the Coating Process on Open Porous Metal Foams

PAMM ◽  
2018 ◽  
Vol 18 (1) ◽  
Author(s):  
Christine Grill ◽  
Anne Jung ◽  
Stefan Diebels
Keyword(s):  
Porous Metal ◽  
Metal Foams ◽  
Modelling And Simulation ◽  
Coating Process

Developing Elastic, Robust, and Highly Porous Metal Foams Using Carbon Nanotube Scaffolds

2020 ◽  
Vol 2 (7) ◽  
pp. 2090-2097
Author(s):  
Zheng Chen ◽  
Xiaohua Zhang ◽  
Pei Cao ◽  
Zhuo Chao ◽  
Dandan Liu ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Porous Metal ◽  
Metal Foams ◽  
Highly Porous

Measurements of Form and Frictional Drags over a Rough Topographic Bank

2014 ◽  
Vol 44 (9) ◽  
pp. 2409-2432 ◽  
Author(s):  
H. W. Wijesekera ◽  
E. Jarosz ◽  
W. J. Teague ◽  
D. W. Wang ◽  
D. B. Fribance ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Low Frequency ◽  
Multiple Time ◽  
Linear Wave ◽  
Frictional Drag ◽  
Form Drag ◽  
Quadratic Drag ◽  
Roughness Elements ◽  
Roughness Lengths ◽  
Surface Generate

Abstract Pressure differences across topography generate a form drag that opposes the flow in the water column, and viscous and pressure forces acting on roughness elements of the topographic surface generate a frictional drag on the bottom. Form drag and bottom roughness lengths were estimated over the East Flower Garden Bank (EFGB) in the Gulf of Mexico by combining an array of bottom pressure measurements and profiles of velocity and turbulent kinetic dissipation rates. The EFGB is a coral bank about 6 km wide and 10 km long located at the shelf edge that rises from 100-m water depth to about 18 m below the sea surface. The average frictional drag coefficient over the entire bank was estimated as 0.006 using roughness lengths that ranged from 0.001 cm for relatively smooth portions of the bank to 1–10 cm for very rough portions over the corals. The measured form drag over the bank showed multiple time-scale variability. Diurnal tides and low-frequency motions with periods ranging from 4 to 17 days generated form drags of about 2000 N m−1 with average drag coefficients ranging between 0.03 and 0.22, which are a factor of 5–35 times larger than the average frictional drag coefficient. Both linear wave and quadratic drag laws have similarities with the observed form drag. The form drag is an important flow retardation mechanism even in the presence of the large frictional drag associated with coral reefs and requires parameterization.

scholarly journals 3D-printed cobalt-chromium porous metal implants showed enhanced bone-implant interface and bone in-growth in a rabbit epiphyseal bone defect model

Bone Reports ◽  
2020 ◽  
Vol 13 ◽  
pp. 100375
Author(s):  
Yu Ning Chim ◽  
Simon Kwoon Ho Chow ◽  
Sze Yi Mak ◽  
Michelle Meng Chen Li ◽  
Bob Ching Hang Yung ◽  
...  
Keyword(s):  
Bone Defect ◽  
Porous Metal ◽  
Cobalt Chromium ◽  
Defect Model ◽  
Bone Implant ◽  
Metal Implants ◽  
3D Printed ◽  
Epiphyseal Bone

scholarly journals Experimental Investigation of Heat Transfer and Pressure Drop in Porous Metal Foams

2006 ◽  
Author(s):  
Oliver Reutter ◽  
Elena Smirnova ◽  
Jo¨rg Sauerhering ◽  
Stefanie Angel ◽  
Thomas Fend ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Metal Powder ◽  
Power Plants ◽  
Flow Characteristics ◽  
Porous Metal ◽  
Metal Foams ◽  
Inconel 625 ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Metal foams made by the SlipReactionFoamSintering (SRFS)-process are investigated. In these foams the pores are produced by a reaction between iron and a weak acid. The generated hydrogen forms pores in a metal powder slurry. These pores remain in the foam after sintering. Also secondary pores are found in these foams because of the sintering of the metal powder slurry. The metal powder base of the foams is Inconel 625 and Hastelloy B. Foam samples with a variety of different porosities of the two metals in the range of about 62% to 87% are used as well as samples made out of sintered metal powder which were not foamed with porosities of around 50%. The motivation for this study is to use these foams as combustion chamber walls in gas fired power plants. By using porous walls effusion cooling can be applied to keep the wall temperatures low. Air is used as a fluid to study the flow characteristics of these samples. Their pressure drop with air at room temperature is measured in the range of velocities of up to around 1 m/s. The parameters characterizing the foams are obtained using the Darcy-Forchheimer equations resulting in the permeability and the inertial coefficients. The dependency on the porosity is discussed. The volumetric heat transfer is measured for the foams by a transient method based on an air flow with a sinusoidal temperature wave, which is attenuated by the sample. The obtained volumetric heat transfer coefficients are discussed and transferred to Nu-Re correlations. Correlations between the heat transfer coefficients and the pressure drop coefficients are made.

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