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In this work, sound absorption phenomena associated with the viscous shear stress within rigid porous media is investigated with a simple isothermal lattice Boltzmann BGK model. Simulations are conducted for different macroscopic material properties such as sample thickness and porosity and the results are compared with the exact analytical solutio...
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Conventional lattice Boltzmann models for the simulation of fluid dynamics are restricted by an error in the stress tensor that is negligible only for small flow velocity and at a singular value of the temperature. To that end, we propose a unified formulation that restores Galilean invariance and the isotropy of the stress tensor by introducing an ex...
Citations
... A rigid porous media was simulated [89], assuming tiny straight channels for the porous media with viscous absorption dominating the process (no slipping back BC) and a periodic primitive cell; see Fig. 9 as a reference. Some macroscopic parameters of the sample, such as porosity and thickness, can be studied by changing the channel geometry. ...
The Lattice Boltzmann Method (LBM) can be applied to several fluid dynamic problems in the time domain. This numerical method indirectly solves the Navier-Stokes equations in a weakly compressible limit that allows acoustic wave propagation. This work presents a systematic literature review concerning the application of the LBM in acoustics. Applications found in the literature are classified and presented in different categories, including wave theory, boundary conditions, sound absorption materials, aeroacoustics, and musical acoustics. The increasing amount of research in recent years about aeroacoustics is remarkable, thanks to the intrinsically coupled treatment of the acoustical field and the mean flow, the potential of studying different wave phenomena such as diffraction and scattering, the easy way to model complex geometric boundaries in 2D and 3D, and finally thanks to the increasing available computational power. Some examples were included to illustrate the LBM capabilities to simulate sound wave phenomena, including point source modeling, diffraction and interference of sound waves, jet noise, and edge noise. This work will give a retrospective of the research developed in the past and a perspective on how this numerical method might evolve in the acoustical field.
... In accordance with the Kyoto Protocol [16] and the Paris Agreement [17] on global climate change, the conversion of agricultural waste into sound-absorbing material could possibly result in a reduction in the consumption of existing synthetic materials, which would then lead to a reduction in the emissions of greenhouse gases (GHG). In addition, these materials are used in a wide range of industries, including aeronautics, construction, and road transportation, as noise must be reduced with the least amount of insulation possible to keep the costs to a minimum [18]. ...
Natural fibers are increasingly being used to make nonwoven fabrics, substituting synthetic materials for environmental and economic reasons. In this study, a series of needle-punched nonwoven fabrics were made by extracting fibers from coffee husks and blending them with a proportion of spinning waste consisting of cotton fibers and another five different natural fibers. This work investigates the coefficient of sound absorption, thermal conductivity, areal density, thickness, and air permeability. Overall, the sound absorption properties of the produced nonwoven fabric depend on the blend proportion and the number of layers. The results from the fabric containing nettle and banana fibers demonstrate a much-improved sound absorption coefficient. These results have been compared with those of commercially available nonwoven fabrics that are manufactured from polyester and polyurethane foam. The thermal conductivities of the fabrics made with nettle and coir were the highest and lowest, respectively. This is because of the fiber linear density, but all in all, fibers extracted from coffee husks show significantly promising potential for scaling up to replace existing synthetic fibers.
... Liu et al. [8] investigated the multisector potential use of agricultural waste in the building construction field, finding different types of final applications: blocks, vegetable biomass for heating, multilayer solutions, particles, coils, panels for the building envelope. The research on sound absorbing materials has become increasingly important throughout the last decades due to several possible fields of applications, from the aeronautics and road transportation industries to construction and buildings [9]. Currently, the main acoustic absorbing materials on the market have huge costs and represent a big issue in terms of final disposal due to their nonbiodegradability [10]. ...
... Liu et al. [8] investigated the multisector potential use of agricultural waste in the building construction field, finding different types of final applications: blocks, vegetable biomass for heating, multi-layer solutions, particles, coils, panels for the building envelope. The research on sound absorbing materials has become increasingly important throughout the last decades due to several possible fields of applications, from the aeronautics and road transportation industries to construction and buildings [9]. Currently, the main acoustic absorbing materials on the market have huge costs and represent a big issue in terms of final disposal due to their non-biodegradability [10]. ...
In order to limit the environmental impact caused by the use of non-renewable resources, a growing research interest is currently being shown in the reuse of agricultural by-products as new raw materials for green building panels. Moreover, the European directives impose the goal of sustainability supporting the investigation of passive solutions for the reduction of energy consumption. Thus, the promotion of innovative building materials for the enhancement of acoustic and thermal insulation of the buildings is an important issue. The aim of the present research was to evaluate the physical, acoustical, and thermal performances of building panels produced by almond skin residues, derived from the industrial processing of almonds. In this paper different mix designs were investigated using polyvinyl acetate glue and gum Arabic solution as binders. Air-flow resistivity σ and normal incidence sound absorption coefficient α were measured by means of a standing wave tube. Thermal conductivity λ, thermal diffusivity α, volumetric heat capacity ρc were measured using a transient plane source device. Finally, water vapor permeability δp was experimentally determined using the dry cup method. Furthermore, a physical characterization of the specimens in terms of bulk density ρb and porosity η allowed to study the correlation existing between the binder and the aggregates and the consequent acoustical and hygrothermal behavior occurring on the different mix designs. The achieved results suggested the investigated materials comparable to the main products currently existing on the market.
... Liu et al. [8] investigated the multisector potential use of agricultural waste in the building construction field, finding different types of final applications: blocks, vegetable biomass for heating, multilayer solutions, particles, coils, panels for the building envelope. The research on sound absorbing materials has become increasingly important throughout the last decades due to several possible fields of applications, from the aeronautics and road transportation industries to construction and buildings [9]. Currently, the main acoustic absorbing materials on the market have huge costs and represent a big issue in terms of final disposal due to their nonbiodegradability [10]. ...
... Liu et al. [8] investigated the multisector potential use of agricultural waste in the building construction field, finding different types of final applications: blocks, vegetable biomass for heating, multi-layer solutions, particles, coils, panels for the building envelope. The research on sound absorbing materials has become increasingly important throughout the last decades due to several possible fields of applications, from the aeronautics and road transportation industries to construction and buildings [9]. Currently, the main acoustic absorbing materials on the market have huge costs and represent a big issue in terms of final disposal due to their non-biodegradability [10]. ...
... In addition, LBM totally avoids the nonlinear advective terms, in contrast to the Navier-Stokes-based methods (Mohamad, 2007). Therefore, the LBM is considered a mature solver for ?ows in porous media and has been successfully applied in modeling complex phenomena in porous media, such as electro-osmotic flows in porous microchannels (Chai et al., 2007), flow in nanoporous media (Li et al., 2013), sound absorption in rigid porous media (Silva et al., 2016), conjugate heat transfer (Abbaszadeh et al., 2017), simulating engineering flows through complex porous media (Krastev and Falcucci, 2018), and many others. ...
The present study deals with natural convection flow in an open-ended cavity partially filled with fibrous porous media. The numerical investigations are performed using the lattice Boltzmann method. The considering porous media is formed of random arrangement of square obstacles and simulated in pore scale. The effects of some dominant variables such as the Rayleigh number, angle of inclination, porosity and the eccentricity of the porous media on the flow field and the cavity heat transfer are investigated. Results are reported in terms of isotherms, streamlines and average Nusselt numbers. The numerical results obtained indicated that appropriate use of porous media can enhance the rate of heat transfer. Also, increasing the inclination angle at high Rayleigh numbers or decreasing the porosity at low Rayleigh numbers, increases the average Nusselt number. Comprehensive discussions on the effectiveness of the porous cavity compared to a nonporous one, at different situations are also provided.
The rapid growth in the agricultural production has generated several environmental impacts with a significant contribution from vegetable waste. A substantial agricultural residue comes from sunflower cultivation, especially sunflower stems, which are used in this research to develop a renewable composite with acoustic properties for insulation panels. The research followed the cleaner production practices and the proposed composite was the result of a mixture of sunflower stalk, plaster, water, and sodium benzoate as a fungal inhibitor. Composites of different particle sizes of sunflower stem were subjected to impedance tube and stress tests. Different mesh sieves with sizes of 1.18 mm, 2.36 mm, 4.75 mm and 6.30 mm were used to standardize the processed material. The acoustic performance of the samples was evaluated in an impedance tube according to the ISO, 19984-2, where frequencies in the range from 100 Hz to 6400 Hz were tested with a tube diameter of 28 mm. The samples were later tested for mechanical stress through a three-point bending test in a threefold scheme as well, following the Brazilian standard ABNT NBR 13279:2005. Statistical analysis through ANOVA and Duncan test (significance level of 5%) proved the best prototype was found to be that of smaller particle size at a sound absorption coefficient of 0.8293. The bending strength of 0.69 MPa was found for the same prototype, which is a reasonable result in comparison to other studies with composite materials. The cost of manufacturing the renewable composite was estimated at 67% lower than that observed with commercial materials. The environmental assessment was found positive as it met the requirements of cleaner production and contributed to the study of composites development from renewable materials.
