scholarly journals Structured Porous Material Design for Passive Flow and Noise Control of Cylinders in Uniform Flow

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2905 ◽  
Author(s):  
Elias J. G. Arcondoulis ◽  
Yu Liu ◽  
Zhiyong Li ◽  
Yannian Yang ◽  
Yong Wang
Keyword(s):  
Porous Medium ◽  
Porous Material ◽  
Porous Structure ◽  
Vortex Shedding ◽  
Noise Control ◽  
Flow Behavior ◽  
Porous Coating ◽  
Numerical Comparison ◽  
Passive Flow ◽  
Coated Cylinder

Cylindrical bodies in uniform flows can be coated with a porous medium as a passive flow and noise control method in an effort to reduce the acoustic effects of vortex shedding. To date, the employed open-cell porous materials typically possess a randomized internal structure. This paper presents the design and validation of a novel 3-D printed structured porous coated cylinder that has significant flexibility, in that the porosity and pores per inch of the porous coating can be modified independently and relatively easily. The performance of the structured porous coating design is compared against porous polyurethane and metal foam with the same coating dimensions and similar pores per inch and porosity via an experimental acoustic investigation, revealing strong similarity in the passive noise control performance of each material type. A numerical comparison illustrates the similarities of the wake structure of the 3-D printed porous coated cylinder to an equivalent Darcy–Forchheimer model simulation that represents a randomized internal porous structure. The performance similarities of these different porous material types indicate that a structured porous geometry can be used to understand the internal flow behavior of the porous medium responsible for reducing the cylinder vortex shedding tone that is otherwise extremely difficult or impossible with typical randomized porous structures. Moreover, significant potential exists for the porous structure to be further optimized or smartly tailored by architectural design for different control purposes, coating geometries and dimensions, and working conditions.

scholarly journals Internal and Near-Wall Flow Fields of a Structured Porous Coated Cylinder and Their Role in Passive Flow and Noise Control

2021 ◽  
Author(s):  
Elias Arcondoulis ◽  
Liu Yu ◽  
Yannian Yang ◽  
Daniele Ragni ◽  
Alejandro Rubio Carpio ◽  
...  
Keyword(s):  
Noise Control ◽  
Flow Fields ◽  
Passive Flow ◽  
Wall Flow ◽  
Coated Cylinder ◽  
Near Wall

Vortex shedding noise and flow mode analysis of cylinder with full/partial porous coating

2020 ◽  
Vol 106 ◽  
pp. 106154
Author(s):  
Zhijie Hu ◽  
Hanru Liu ◽  
Nanshu Chen ◽  
Jiawei Hu ◽  
Fan Tong
Keyword(s):  
Vortex Shedding ◽  
Mode Analysis ◽  
Porous Coating ◽  
Flow Mode ◽  
Vortex Shedding Noise

Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

2005 ◽  
Vol 127 (1) ◽  
pp. 136-144 ◽  
Author(s):  
Yahya Dogu
Keyword(s):  
Porous Medium ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Force Balance ◽  
Complex Flow ◽  
Blow Down ◽  
Permeability Coefficients ◽  
Backing Plate ◽  
Brush Seal

The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis, and bristle flutter. In this study, an axisymmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data: leakage, axial pressure on the rotor surface, and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for the fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while the fence height region is free to spread and bend in the axial direction. It is found that flow resistance for the upper region should be 20% higher than the fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.

scholarly journals COMPUTATIONAL MODELING OF RTM AND LRTM PROCESSES APPLIED TO COMPLEX GEOMETRIES

2012 ◽  
Vol 11 (1-2) ◽  
pp. 93 ◽  
Author(s):  
J. Da S. Porto ◽  
M. Letzow ◽  
E. D. Dos Santos ◽  
S. C. Amico ◽  
J. A. Souza ◽  
...  
Keyword(s):  
Porous Medium ◽  
Flow Behavior ◽  
Resin Transfer Molding ◽  
Three Dimensional ◽  
Complex Geometries ◽  
Resin Flow ◽  
Transfer Molding ◽  
Rtm Process ◽  
General Terms ◽  
Filling Time

Light Resin Transfer Molding (LRTM) is a variation of the conventional manufacturing process known as Resin Transfer Molding (RTM). In general terms, these manufacturing processes consist of a closed mould with a preplaced fibrous preform through which a polymeric resin is injected, filling the mold completely, producing parts with complex geometries (in general) and good finish. Those processes differ, among other aspects, in the way that injection occurs. In the RTM process the resin is injected through discrete points whereas in LRTM it is injected into an empty channel (with no porous medium) which surrounds the entire mold perimeter. There are several numerical studies involving the RTM process but LRTM has not been explored enough by the scientific community. Based on that, this work proposes a numerical model developed in the FLUENT package to study the resin flow behavior in the LRTM process. Darcy’s law and Volume of Fluid method (VOF) are used to treat the interaction between air and resin during the flow in the porous medium, i.e. the mold filling problem. Moreover, two three-dimensional geometries were numerically simulated considering the RTM and LRTM processes. It was possible to note the huge differences about resin flow behavior and filling time between these processes to manufacture the same parts.

Thermal Shock Behavior and Bonding Strength of MoSi2-BaO-Al2O3-SiO2 Gradient Porous Coating with Polymethyl Methacrylate Addition for Porous Fibrous Insulations

2018 ◽  
Vol 281 ◽  
pp. 493-498
Author(s):  
Ya Yu Su ◽  
Xiao Lei Li ◽  
Hui Jie Tang ◽  
Zhi Hao Zhao ◽  
Jian He
Keyword(s):  
Porous Structure ◽  
Thermal Shock ◽  
Bonding Strength ◽  
Thermal Shock Resistance ◽  
Porous Coating ◽  
Bonding Layer ◽  
Interface Bonding ◽  
Shock Resistance ◽  
Thermal Shock Behavior ◽  
Interface Bonding Strength

In order to improve the thermal shock behavior of high temperature resistant coating on porous fibrous referactory insulations, the MoSi2-BaO-Al2O3-SiO2(MoSi2-BAS) gradient porous coatings were designed by preparing a dense surface layer and a porous bonding layer with the method of brushing and subsequent sintering at 1773 K. The porous bonding layer was obtained by adding polymethyl methacrylate (PMMA) as pore former. As the content of PMMA increases, the MoSi2-BAS coatings changed from a dense structure into a gradient porous structure. The interface bonding strength and thermal shock resistance of the MoSi2-BAS coatings were investigated. The result shows that the as-prepared coating with gradient porous structure exhibited excellent thermal shock resistance, which remained gradient structure without cracking after thermal cycling 100 times between 1773 K and room temperature. And the interface bonding strength of the gradient porous coating reached 1.5±0.08 Mpa, which was much better than that of the dense coating.

Deterioration in Strength of Brittle-State Porous Bodies

1965 ◽  
Vol 32 (1) ◽  
pp. 43-46 ◽  
Author(s):  
P. C. Huang
Keyword(s):  
Porous Medium ◽  
Porous Material ◽  
Residual Strength ◽  
Modulus Of Elasticity ◽  
Room Temperature ◽  
Density Ratio ◽  
Material Function ◽  
Porous Bodies ◽  
Degradation Factor ◽  
Brittle State

A theory is presented to predict the deterioration in strength for a structure composed of a brittle-state porous material which has been subjected to a damaging tension field. Based on the theory, a degradation factor can be formulated as a means of evaluating the residual strength numerically. A proposed material function for a brittle-state porous medium was evaluated experimentally and was found to be satisfactory for an alumina material. The modulus of elasticity at room temperature of the same material has been found to increase with the density ratio in semi-logarithmic form.

Investigation of the Effect of Porous Material on the Flow and Temperature Patterns of a Passive Solar Air Heater

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Digpal Kumar ◽  
B. Premachandran
Keyword(s):  
Heat Flux ◽  
Porous Medium ◽  
Porous Material ◽  
Constant Heat Flux ◽  
Surface Radiation ◽  
Electrical Heating ◽  
Solar Air Heater ◽  
Air Heater ◽  
The Difference ◽  
Drying Chamber

Abstract In this work, the effect of flow resistance due to the presence of porous medium representing agricultural products at the exit of free convection-based solar air heater is studied experimentally and numerically. An air heater, along with the drying chamber, is designed as an inclined channel to conduct the experiments. Constant heat flux condition is provided by electrical heating on the top absorber plate of the channel. Experiments are conducted for heat flux ranging from 250 to 750 W/m2 for the channel inclination angle of 30 deg. Porous material bed height is also varied in the drying chamber, while porosity is set at 0.36. The surface-to-surface radiation model is considered for modeling of heat transfer within the flow. For all the heat flux values considered in the experiments, numerical simulations are performed at three different angles of inclinations of 15 deg, 30 deg, and 45 deg. In this analysis, the temperature distribution in the channel wall, the flow pattern, the difference in the mass flowrate, and temperature of the outlet air are investigated with different heights of the porous medium.

scholarly journals Effects of non-uniform permeability on vortex shedding and noise control of blunt trailing edge

AIP Advances ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 085018 ◽  
Author(s):  
Hanru Liu ◽  
Nanshu Chen ◽  
Zhijie Hu
Keyword(s):  
Vortex Shedding ◽  
Noise Control ◽  
Trailing Edge ◽  
Blunt Trailing Edge
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