Porous Block Research Articles

Numerical investigation on the wave dissipating performance due to multiple porous structures

ABSTRACT Gravity wave interaction with porous structures is investigated under the assumption of linearized wave theory. Multiple porous blocks of finite thickness with finite spacing are investigated under the action of oblique ocean waves considering leeward unbounded region and confined region. The eigenfunction expansion method is employed to analyse the effect of multiple-confined regions in the trapping of oblique waves. The study outcomes are validated with numerical and experimental results available in the literature. The friction factor and the inertia effect of the porous medium are considered and different porosity conditions are adopted to determine the wave reflection coefficient, transmission coefficient, wave dissipation and wave force impact on the leeward wall. The functional efficiency of multiple fully extended porous structures is studied for different values of porosity, water chamber length, angle of incidence, friction factor and spacing between the porous blocks. The seabed is assumed to be uniform impermeable bottom and uneven bottom (step approximation is adopted). The study demonstrates that the better wave blocking is achieved with the increase in the series of porous structures and the confined regions can be used effectively for the trapping of oblique waves. The present study will be helpful in the design of porous structures for security of coastal facilities and coastal structures in offshore environment.

Research on the Adsorption Behavior of Heavy Metal Ions by Porous Material Prepared with Silicate Tailings

Tailings generated from mineral processing have attracted worldwide concerns due to creating serious environmental pollution. In this work, porous adsorbents were prepared as a porous block by using silicate tailings, which can adsorb heavy metal ions from the solution and are easy to separate. The synthesized silicate porous material (SPM) was characterized by X-ray diffraction (XRD), Brunner–Emmet–Teller (BET), and scanning electron microscope (SEM). The material presented a surface area of 3.40 m2⸱g−1, a porosity of 54%, and the compressive strength of 0.6 MPa. The maximum adsorption capacities of Pb2+, Cd2+, and Cu2+ by SPM were 44.83 mg·g−1, 35.36 mg·g−1, and 32.26 mg·g−1, respectively. The experimental data were fitted well by the Freundlich and Langmuir adsorption models. The kinetics of the adsorption process were fitted well by the pseudo-first order kinetic equation. These results show that the porous materials prepared with silicate tailings could act as an effective and low-cost adsorbent for the removal of heavy metal ions from wastewater. This study may provide a new thought on the high-value utilization of tailing for alleviating environmental pressure.

Vertical ridge augmentation using a porous composite of uncalcined hydroxyapatite and poly-DL-lactide enriched with types 1 and 3 collagen

BackgroundPrevious studies have shown that porous composite blocks containing uncalcined hydroxyapatite (u-HA; 70 wt%) with a scaffold of poly-DL-lactide (PDLLA, 30 wt%) are biodegradable, encourage appropriate bone formation, and are suitable for use as a bone substitute in vertical ridge augmentation. The present study aimed to accelerate osteogenesis in vertical ridge formation by adding types 1 and 3 collagen to the u-HA/PDLLA blocks and assessing the effect.Material and methodsThe bone substitute in the present study comprised porous composite blocks of u-HA (70 wt%) with a PDLLA (27–29 wt%) scaffold and enriched with types 1 and 3 collagen (1.7 ~ 3.4 wt%). The control blocks were composed of u-HA (70 wt%) and PDLLA (30 wt%). The materials were formed into 8-mm diameter, 2-mm high discs and implanted onto the cranial bones of six rabbits. The animals were sacrificed 4 weeks after implantation, and histological and histomorphometrical analyses were performed to quantitatively evaluate newly formed bone.ResultsNew bone formation occurred with both block types, showing direct contact with the original bone. Mean ± standard deviation bone formation was significantly greater in the experimental blocks (25.6% ± 4.8%) than in the control blocks (17.0% ± 4.7%).ConclusionsHistological and histomorphometrical observations indicated that new bone was formed with both block types. The u-HA/PDLLA block with types 1 and 3 collagen is a more promising candidate for vertical ridge augmentation than the u-HA/PDLLA alone block.

Fabrication and Characterization of Porous Bioceramic Made from Bovine Bone Powder Mixed Calcium Phosphate Glass

Bovine bone xenograft was selected bioactive material currently widespread acceptable for using as human bone void filler. In this paper we described a new porous bioceramic block fabricated from bovine bone powders mixed with calcium phosphate glass. The characterized methods were atomic absorption spectrometer, x-ray diffraction, scanning electron microscope, energy dispersion x-ray spectroscopy, diffusion test, bending test, compressive test and Archimedes’ principle. The final products showed interconnecting pores size range 100 to 500 mm, apparent porosity about 52% and mole ratio of Ca:P as 1.65. The toxic elements such as arsenic, cadmium, mercury, and lead were lower standard limits of ASTM I (American Society for Testing and Materials International). The samples had a compressive strength more than 400 kg/cm2. So, this object can be useful as an alternative choice for human bone substitute in the vertical compression load bearing area.

Modeling impact pressure on the surface of porous structure by macroscopic mesh-free method

In this study, the impacting force on the face of porous structure is investigated by using the mesh-free macroscopic model. To achieve this, the mesh-free macroscopic approach of Moving Particle Semi-implicit method (MPS) is redeveloped. Firstly, a stabilization technique is used in the method to eliminate numerical noise. Secondly, the spatial discretization operators employ a porosity-based coefficient to account for the representative volume to model fluid flows in the porous media. More importantly, an improved numerical technique is proposed to overcome abrupt porosity change at the boundary between the porous and non-porous regions. The numerical model is validated by the dam-breaking waves through porous blocks and flows over porous weirs, in which the simulated free-surface profiles are in good agreement with experimental measurements. By applying the method, how the porosity and mean diameter of porous materials play a role in impacting pressure and wave height for dam-breaking flow through porous block is investigated. It is found that the porous materials with a larger porosity or larger mean diameter are able to easily permit water penetration through the porous media while the impacting pressure at the interface and reflected wave height can be reduced.

Multi-functional carbon integrated rGO-Fe3O4@C composites as porous building blocks to construct anode with high cell capacity and high areal capacity for lithium ion batteries

For lithium ion batteries (LIBs), a high cell capacity, which requires both a high capacity and a high loading mass of active materials, is crucial for practical application. However, how to fabricate efficient anodes with high cell capacity and high areal capacity remains a challenge. To solve this issue, we design a structure of porous building block composed of multi-functional carbon integrated rGO-Fe3O4@C composites. The carbon shell of Fe3O4@C derived from polydopamine (PDA) acts as an artificial solid electrolyte interface (SEI) film to avoid the excessive SEI formation, within which there are sufficient lithium ion diffusion pathways derived from the spaces between Fe3O4 nanocrystals. The carbon derived from the in-situ polymerized polyacrylamide and rGO act as a glue to integrate the as-obtained Fe3O4@C composites to form the porous building blocks. Due to the compact stacking of building blocks, the composite electrode achieves a high active material loading mass of 5.94mg (5.25mgcm−2), while maintains a satisfying capacity (685mAhg−1 after the 100th cycle at 0.5Ag−1) and good rate performance (440mAhg−1 at 3C). Therefore, a high cell capacity (4.02mAh) and a high areal capacity (3.6mAhcm−2) at 2.62mAcm−2 in a single CR2032 coin cell are achieved.

Preparation of silica–poly(methyl methacrylate) composite with a nanoscale dual-network structure and hardness comparable to human enamel

ObjectiveThis study aims to prepare an organic–inorganic composite with a nanoscale dual-network structure composed of a ceramic skeleton and infiltrated resin to mimic the mechanical properties of human enamel. MethodsA porous silica block was obtained by sintering a green body composed of SiO2 nanoparticles and poly(vinyl alcohol) organic binder. Methyl methacrylate monomers were infiltrated into the porous silica block and thermally polymerized to form poly(methyl methacrylate) (PMMA). A monolithic SiO2–PMMA composite was obtained, and its nanoscale structure was investigated. Its mechanical properties were characterized by Vickers hardness, elastic modulus, and flexural strength tests. ResultsThe SiO2–PMMA composite had a nanoscale dual-network structure composed of a silica–ceramic skeleton with PMMA-filled continuous 10–20 nm sized pores. The mechanical properties of the composite depended on the SiO2 content, which could be adjusted by modifying sintering time of the porous silica block. The mechanical properties of the composite exhibited wide variations with Vickers hardness values of 54–756, elastic moduli of 7–54 GPa, and flexural strengths of 75–120 MPa. SignificanceThe preparation of a SiO2–PMMA composite with a dual-network structure at the nanoscale was demonstrated, and the composite was characterized with respect to its hardness compatibility with human enamel.

Study on the hygrothermal properties of a Chinese solar greenhouse with a straw block north wall

New types of straw block (types I and II straw blocks) were developed and applied in the north wall of solar greenhouses. The hygrothermal and fungistatic properties of the new types of straw block were researched, and the thermal and wet environment of a solar greenhouse with a north wall formed from new types of straw block (STG) was measured. The thermal properties of the new types of straw block north wall (ST) were higher than those of a porous clay block north wall (CL). The pH values of the extracted liquids of the types I and II straw blocks were 13 and 11.5, respectively, making it difficult for mycelia to grow on these blocks. At the depths of 0, 80, 160 and 240 mm, the temperatures of ST were 0.5, 0.6, 0.8 and 1.2℃ higher than those of CL, respectively. Compared to the solar greenhouse with a porous clay block north wall (CLG), the air temperature of STG was 0.5℃ higher during nighttime, and the average relative humidity was 5.3% lower during nighttime. The research shows that the STG has better thermal and wet environment characteristics, and it is durable and suitable for the growth of crops.

Autonomous Soil Water Content Sensors Based on Bipolar Transistors Encapsulated in Porous Ceramic Blocks

We present an autonomous sensor to measure soil water content that uses a single heat pulse probe based on a transistor encapsulated in a porous block. The sensor uses a bipolar junction transistor, which performs as both a heating and temperature-sensing element. Since the sensor depends on a porous block to measure the matric potential of the soil, it does not suffer from accuracy problems if the contact between the probe and the soil is not perfect. A prototype of the sensor showed a temperature variation of Δ T = 2.9 ∘ C when the porous ceramic was saturated with water. The sensor presented an almost linear behavior for small changes in the matric potential of a red latosol when tested in the 1-kPa and 35-kPa pressure range, showing a sensitivity of S = 0.015 ∘ C/kPa. The ultra-low power signal conditioning circuit can read the sensor’s temperature with a resolution of approximately 0.02 ∘ C, so the matric potential can be read in increments of at least 1.33 kPa. When powered only by a 2-F supercapacitor from the energy-harvesting system, the interrogation circuit is able to take one soil water content measurement per day, for eleven days.

Mass transfer in proton exchange membrane fuel cells with baffled flow channels and a porous‐blocked baffled flow channel design

In proton exchange membrane fuel cells, baffled flow channels enhance the reactant transfer from flow channels to gas diffusion layers. However, the reactant transfer depends on both the diffusive transfer and convective transfer, and how the baffles in flow channels affect them is still unknown. Therefore, in this work, a two-dimensional, two-phase, nonisothermal, and steady-state model of proton exchange membrane fuel cells is developed, and these two transfer processes from flow channels to gas diffusion layers are comparatively studied. Simulation results show that first of all, the reactant transfer from flow channels to gas diffusion layers mainly depends on the diffusive transfer. Therefore, if the desire is to enhance the mass transfer from flow channels to gas diffusion layers, the diffusive mass transfer should be enhanced firstly. Being guided by this goal, a porous-blocked baffled flow channel is developed. This flow channel design can further enhance the reactant transfer from flow channels to gas diffusion layers, and the cell performance can be improved. Moreover, when the porosities of porous blocks at the front place of flow channels are lower, the cell power is also increased but the pumping power can be reduced a lot.

Interfacial dynamics of immiscible binary fluids through ordered porous media: The interplay of thermal and electric fields

We report the interplay of electrical and thermal fields on the interfacial dynamics of two immiscible fluids inside a periodic porous domain. The alternating current electrothermal mechanism is employed to generate the two phase flow. The surfaces of the porous blocks are wetted with wettability conditions which are manifested by a predefined static contact angle. Depending on the surface affinity and the electrical parameters, two distinctive spatio-temporal regimes can be identified, namely, trapping of the displaced fluid between the two consecutive porous blocks (formation of liquid bridge) and merging of contact lines after traveling the obstacle (complete interface recovery). Results show that liquid bridge formation and complete interface recovery are strongly influenced by the viscosity and thermal conductivity contrasts, in addition to the relevant electro-thermal parameters.

Exploring the binding effect of a seaweed-based gum in the fabrication of hydroxyapatite scaffolds for biomedical applications

ABSTRACTHydroxyapatite (HAP) is the most bountiful mineral found in the bones and teeth of vertebrates. They are extensively used in therapeutic applications as an implant substrate to augment bone progress or as a drug release vehicle due to its close similarity to the components of human bones and also for its outstanding biocompatibility. The porous blocks are commonly used as a scaffolding substrate. Various methods have been applied to construct HAP porous scaffolds. The present study investigates the binding properties of a seaweed-based biopolymer, sodium alginate as a natural binder in the fabrication of HAP scaffolds by polymeric replication technique. These porous scaffolds were characteristics by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Stereo zoom optical microscopy image and compressive mechanical testing techniques. The bioactivity of the scaffolds was evaluated by immersing them in simulated body fluid (SBF). Thus, scaffolds with highly interconnected macropores, with pore diameter around 300 nm to 500nm and micropore mainly fall within the 2–20 μm range can be obtained, which are suitable for absorption of biological metabolites and the cell attachment. Also, the maximum compressive yield strength at break down was found to be 1.4MPa for 68% porous scaffold, comparable to that of cancellous bones.

The homogenized Kondaurov type non-equilibrium model of two-phase flow in multiscale non-homogeneous media

The goal of the paper is to derive a homogenized model of the incompressible two-phase flow in multiscale porous media made of disjoint non-homogeneous porous blocks surrounded by highly permeable connected porous subspace which is regarded as a fracture system. The nonhomogeneity of the porous blocks means that they contain the inclusions with contrast properties. The upscaling process is done in two steps. At the first step a Kondaurov type non-equilibrium flow model on the mesoscale level is derived. This model takes into account the capillary non-equilibrium phenomena of the flow in the blocks and fractures. Upscaling the mesoscale model, we obtain the desired macroscopic (homogenized) Kondaurovs type model. The upscaling process at the second step is justified by the numerical simulation.

Experimental Study on Mechanical Properties of Permeable Concrete

The mechanical properties of permeable concrete are mainly affected by the water-cement ratio and coarse aggregate gradation. In order to further clarify the relationship between the tensile strength and compressive strength of porous concrete and the above-mentioned influencing factors, the test pieces of different test ratios were tested by preparing porous concrete test blocks and using RFPA2D numerical simulation method. The results show that the tensile and compressive strength of the permeable concrete gradually decreases with the increase of the water-cement ratio under the same conditions of coarse aggregate gradation. In the case of the same water-cement ratio, the tensile and compressive strength of the permeable concrete gradually increases as the particle size of the coarse aggregate increases. The larger the coarse aggregate particle size, the greater the increase in tensile strength.

Integrated Numerical Simulation of Water Resources in Crystalline Aquifers at Koué Watershed Scale (Western Côte d’Ivoire)

The present work applied the HydroGeoSphere (HGS) model in humid tropical area to Koue watershed scale to simulate flows in porous and fractured area of crystalline aquifers. It integrates rainfall, physiographic, fractures, hydraulic drilling and hydrodynamic data. The simulation of flows in porous area concerned 5 test zones. The input database of the model is implemented on a triangular grid in porous area using Gridbuilder software and interactive block grid in fractured area. In order to use the model in these two environments, boundary condition was set. The infiltrations rate of the earth layers is estimated in the order to 10-5 ms-1. The model simulates the pumping with a good reproductivity of the drawdown profiles of groundwater at the drillings. The storage coefficients vary between 9.9 × 10-4 and 2 × 10-3. The hydraulic conductivities vary from 8.5 × 10-6 to 2 × 10-5. 73.9% of the drillings studied has a high hydraulic conductivity and shows a strong drawdown of the groundwater table. The study of the static levels of the ground water allowed indicating the distribution of the water resources in the drillings: 57% are deep in the first 10 meters, 36% between 10 and 20 m, and 7% in the higher level to 20 m deep in the earth.

A Feasibility Study of Wood-plastic Composite Paver Block for Basic Rest Areas

A wood-plastic composite (WPC) paver block was manufactured using wood chips waste through an extrusion process, and it was intended to be used for paving in basic rest areas. The first stage in this study covered preliminary tests in terms of flexural strength and dimensional swelling to determine the optimal WPC compounding mix condition, by variation of the WPC ingredients. Next, three different paver blocks including the WPC block, a non-porous cement block, and a porous cement block were tested in terms of various material properties in the laboratory. Finally, two outdoor test sections of the proposed paver blocks were prepared to simulate a basic rest area. Test results indicated that the flexural strength of the WPC paver blocks was about 1.6 times greater than that of the tested cement paver blocks. The WPC block pavement was unaffected by water buoyance as well as volume expansion due to swelling. Results from the impact absorbance test and light falling weight deflectometer (LFWD) test clearly showed that the WPC block paving system marginally satisfied the comfortable and safe hardness range from the pedestrians’ perspective, while the results demonstrated that it is structurally sound for application as a road paving block.

Numerical study of wave interaction with a composite breakwater located on permeable bed

The response of a composite breakwater against wave load is numerically investigated using Smoothed Particle Hydrodynamic (SPH) model. Permeability of the stone layer beneath the caisson is implemented in the model and a new scheme free of any tuning parameter is introduced to estimate the dynamic friction forces transitionally applied to the moving caisson. To overcome pressure noises inside the porous medium, a treatment based on δ-SPH scheme is utilized and its performance is verified by modeling a simple hydrostatic condition inside a homogeneous porous medium. The model ability in simulating fluid flow through porous media is approved by modeling dam break flow through a porous block. In addition, a caisson breakwater with an impermeable bed is modeled and the results are compared with experimental and other numerical results to validate the performance of the introduced friction coefficient. Then, the same caisson but with a permeable bed is simulated against the incident waves and the horizontal forces as well as sliding displacements are calculated. Good agreements with the experimental data show the acceptable performance of the developed model as well as the importance level of the permeable bed on the caisson response. Based on the results, neglecting the flow through the porous bed of the caisson may result in an overestimated wave force and an underestimated caisson sliding. Finally, the caisson responses to different wave conditions are studied and it is shown that the peak load on the caisson increases as the wave height or wave period rises.

Unsteady Pulsatile Hydromagnetic Counter-Current Flows of Cu–Water and CuO–Water Nanofluids Through Two Elastic Coaxial Pipes with Porous Blocks

In the present work, we study pulsatile magnetohydrodynamic mixed convection counter-current flows of Cu–Water and CuO–Water nanofluids through two elastic coaxial pipes with wall-mounted porous blocks. A two-phase model that takes the effects of Brownian motion and thermophoresis into consideration is used to describe the transfer of heat and the transport of nanoparticles within each nanofluid. The mixed finite element method with $$P_{2}-P_{1}$$ Taylor-Hood elements is employed in order to numerically solve the governing equations with the associated initial and boundary conditions. This numerical solution is used to investigate the effects of porous block thickness, Darcy number, ratio of the radii of the inner and outer channels, Hartmann number and Grashof number on heat transfer, fluid flow, nanoparticle concentration and pressure drop.

Application of Talc as an Eco-Friendly Additive to Improve the Structural Behavior of Porous Concrete

Talc is an eco-friendly material used in various domains. In this study, talc, quartz and lime sand were added for improving the performance of porous concrete. For this, talc/quartz and lime sand were used as substitute with 5–30% and 5–15% of aggregates, respectively. Compressive strength, porosity and permeability of the porous concrete blocks and their draining capacity were the tested characteristics. Results showed that although by increasing the amount of talc, quartz and lime sand, compressive strength was improved, permeability and porosity were reduced. However, despite the significant difference in hardness of talc and quartz, mixtures containing talc had acceptable performance and were close to quartz so that the average compressive strength of talc samples was only 0.4 MPa less than the quartz ones. It was also found that threshold value for the addition of talc to increase the strength of porous concrete was 25% and over this rate makes no difference in resistance and even reduces it. Results also revealed that all mixtures had good performance in drainage of synthetic urban runoff—the least-permeable talc sample drained 40-mm runoff in 69 s. Also, the most impermeable quartz specimen drained the 40-mm runoff in 44 s. Generally, the mentioned results indicated that talc, as an eco-friendly additive, had acceptable performance in improving the properties of porous concrete.

One-step preparation of polyimide-inlaid amine-rich porous organic block copolymer for efficient removal of chlorophenols from aqueous solution

A novel polyimide-inlaid amine-rich porous organic block copolymer (PI-b-ARPOP) was prepared via one-step polymerization by using different molar ratios of melamine (MA)/terephthalaldehyde (TA)/pyromellitic dianhydride (PMDA), at molar ratios of 4/3/1, 4/2/2 and 4/1/3. The copolymer contained both aminal groups belonging to ARPOP and imide groups belonging to PI, and the bonding styles of the monomers and growth orientations of the polymeric chains were diversiform, forming an excellent porous structure. Notably, MA/TA/PMDA (4/2/2) had a surface area and pore volume of 487.27 m2/g and 1.169 cm3/g, respectively. The adsorption performance of the materials towards 2,4-dichlorophenol (2,4-DCP) in ultra-pure water was systematically studied. The pH value of 7 was optimal in aqueous solution. Na+ and Cl− ions did not negatively affect the adsorption process, while humic acid (HA) slightly decreased the capacity. The equilibrium time was 40 sec, and the maximum adsorption capacity reached 282.49 mg/g at 298 K. The removal process was endothermic and spontaneous, and the copolymer could maintain its porous structure and consistent performance after regeneration by treatment with alkali. Moreover, to further assess the practical applicability of the material, the adsorption performance towards 2,4-DCP in river water was also investigated. This paper demonstrated that the PI-b-ARPOP can be an efficient and practical adsorbent to remove chlorophenols from aqueous solution.