Volume Fraction Distribution Research Articles

Parametric investigations on dynamic responses of porous functionally graded al/al2o3 plates: effects of homogenization models and material distributions

This study presents a numerical analysis of the dynamic responses exhibited by functionally graded Al/Al2O3 plates that incorporate porosity. It explores the influence of critical parameters such as the thickness-to-span ratio and the porosity coefficient on the non-dimensional fundamental frequencies. Various micromechanical homogenization models, including Voigt, Mori-Tanaka, LRVE, Tamura, and Reuss, are utilized in conjunction with different material volume fraction distribution profiles: Power-law, Viola-Tornabene four-parameter, and Trigonometric. The research considers four distinct porosity variation patterns: uniform, non-uniform, logarithmic non-uniform, and mass-density. The governing equations are addressed using the Navier solution technique. The findings indicate that the Viola-Tornabene model results in the highest fundamental frequencies, succeeded by the Power-law and Trigonometric models. Among the porosity patterns, mass-density porosity yields the maximum frequencies, whereas uniform porosity leads to the lowest. Furthermore, an increase in the porosity coefficient typically raises the frequencies, with the exception of uniform porosity, while an increase in the thickness-to-span ratio results in a reduction of frequencies across all models. These insights are essential for the optimization of designs for functionally graded porous plates.

Insight into particle size distribution and particle-scale reactions in a supercritical water fluidized bed reactor by CPFD method

Supercritical water gasification (SCWG) provides a promising solution for converting coal into hydrogen-rich gaseous. However, the modelling of the coal SCWG process still poses challenges due to the heterogeneous particle distribution, large quantity of particles, and complex chemical reactions. This study presents a novel three-dimensional numerical model based on computational particle fluid dynamics (CPFD) to study coal particle gasification in the reactor. The model integrates realistic coal particle size distribution, heat and mass transfer phenomena alongside heterogeneous/homogeneous chemical reactions across phases, elucidating multi-scale reacting flow behaviors and illustrating particle volume fraction, size, and velocity distributions. The obtained results reveal the evolution of coal composition, particle scale gasification process, and distribution of gaseous product components in the supercritical fluidized bed reactor. This work aims to serve as a reference for understanding the flow and heat transfer phenomena between supercritical water and coal particles in SCWG reactors.

NUMERICAL MODELING OF TWO-PHASE HEAT TRANSFER DURING EVAPORATION AND CONDENSATION INSIDE A SOLAR STILL

This research presents a comparative analysis of two solar still configurations utilizing the ANSYS 2023R2 software package for computational fluid dynamics (CFD) simulations. The study employs the Volume of Fluid (VoF) model to simulate phase transitions between liquid and vapor, specifically focusing on vaporization processes. It is important to note that the VoF model used in this study primarily serves to visualize vaporization, with its numerical results aligning with theoretical expectations rather than providing practical applications. The relevance of this research is underscored by the global drinking water crisis, which drives the need to enhance the efficiency of desalination systems. Solar distillation is recognized as one of the most environmentally sustainable methods for producing clean water, making it an appropriate focus for this investigation. The primary objective of this work is to conduct a numerical analysis of the solar still, compare the performance of two different configurations, and evaluate potential modifications to improve the system's efficiency. The study simulates heat transfer processes within the distiller, the distribution of vapor volume fractions, and temperature variations over time. The findings indicate that the dual-slope configuration outperforms the single-slope configuration in terms of efficiency and productivity. Additionally, the research provides insights into the physical processes occurring within the distiller and identifies potential areas for further refinement of the system's modeling in ANSYS.

Computational comparison of passive control for cavitation suppression on cambered hydrofoils in sheet, cloud, and supercavitation regimes

Cavitation is a transient, highly complex phenomenon found in numerous applications and can have a significant impact on the characteristics as well as the performance of the hydrofoils. This study compares the evolution of transient cavitating flow over a NACA4412(base) (NACA stands for National Advisory Committee for Aeronautics) cambered hydrofoil and over the same hydrofoil modified with a pimple and a finite (circular) trailing edge. The assessment covers sheet, cloud, and supercavitation regimes at an 8° angle of attack and the Reynolds number of 1×106, with cavitation numbers ranging from 0.9 to 0.2. The study aims to comprehensively understand the role of the rectangular pimple in controlling cavitation and its impact on hydrodynamic performance across these regimes. Numerical simulations were performed using a realizable model and the Zwart–Gerber–Belamri (ZGB) cavitation model to resolve turbulence and cavitation effects. The accuracy of the present numerical predictions has been verified both quantitatively and qualitatively with available experimental results. The present analysis includes the time evolution of cavities, temporal variation in total cavity volume, time-averaged total cavity volume, distributions of vapor volume fractions along the chord length, and their hydrodynamic performance parameters. Results demonstrate that rectangular pimples have significant impacts in the different cavitation regimes. In the sheet cavitation regime (σ=0.9), the NACA4412(pimpled) hydrofoil exhibits minimal cavity length and transient volume changes as compared to the NACA4412(base) hydrofoil. In the cloud cavitation regimes (σ=0.5), cavity initiation occurs differently, starting from the pimpled location for the NACA4412(pimpled) hydrofoil, unlike the initiation just downstream of the nose in the case of base hydrofoil. In the supercavitation regimes (σ=0.2), the cavity length remains comparable, but the NACA4412(pimpled) hydrofoil exhibits larger cavity volume evolution in both cloud and supercavitation regimes (σ=0.5 and σ=0.2) after initial fluctuations. Furthermore, hydrodynamic performance for the NACA4412(pimpled) hydrofoil shows 41%, 36%, and 17% lower lift coefficients, and 46%, 27%, and 9% lower drag coefficients in sheet, cloud, and supercavitation, respectively.

Numerical investigation on cavitation erosion and evolution of choked flow in a tri-eccentric butterfly valve

The tri-eccentric butterfly valve is widely utilized in the petrochemical, nuclear, and metallurgy industries due to its robust sealing performance and great pressure resistance. When the local static pressure is lower than the saturation vapor pressure, the fluid phase is transformed into vapor, and cavitation occurs. Cavitation intensifies and the bubbles generated by cavitation severely hinder the flow when the inlet pressure remains constant and the outlet pressure further decreases. This phenomenon is known as choked flow. Choked flow is a derivative phenomenon of cavitation, which seriously threatens the lifetime of valves and the safety of the operation system. In this paper, a multiphase flow of the tri-eccentric butterfly valve is modeled to investigate the choked flow characteristics. The numerical results based on the proposed model are in good agreement with the experiments. The effect of the pressure drop on the mass flow rate and flow coefficient is studied and the liquid pressure recovery factor of the tri-eccentric butterfly is determined at the certain valve opening degree based on the Schnerr and Sauer cavitation model. The relationship between the pressure ratio and choked flow is studied by pressure and velocity contours. The susceptible erosion locations and primary causes of erosion for the butterfly valve at the certain valve opening degree are investigated. By comparison of the distribution of the vapor volume fraction and vortex structures, the spatial correlation between vortex and choked flow is revealed. Meanwhile, the effect of the pressure ratios on the average vapor volume fraction at 70% and 100% valve opening degrees is studied. The evolution of choked flow in the tri-eccentric butterfly is revealed and the cause of choking is pointed out.

Numerical study on the thermal performance of space radiator using microencapsulated phase change material slurry as working medium

Microencapsulated phase change material slurry (MPCMS) has good prospects in the field of heat transfer because of its high latent heat and stability. In this research, MPCMS is applied to a space radiator to increase its heat load and temperature stability. The thermal performance of the space radiator is numerically studied by using the two-phase Eulerian (TPE) model and a multi-scale coupling model. The effects of velocity, volume fraction, microcapsule size, and microcapsule size distribution on the thermal performance of the space radiator are studied. Results show that the temperature flat area in the tube increases with the increase in the volume fraction or flow rate of the particle phase in the MPCMS, which means the heat dissipation capacity of the space radiator is also enhanced, and the maximum increase is 14 %. Compared with the use of pure water, the temperature difference between the highest and the lowest temperature of the radiator surface can be reduced by 40 %, and the heat dissipation power can be increased by 5 %. In addition, the large size of microcapsules limits the heat transfer between the two phases, especially when the size is greater than 50 μm. Compared with uniform microcapsule size distribution, the effect of lognormal distribution of variance σ = 0.7 on heat transfer is less than 1 %.

Preparation and formation mechanism of (W) WC/Fe bundle reinforced iron matrix composites

To address the issue of strength and toughness inversion in traditional metal matrix composites, which are reinforced by uniformly distributed ceramic particles, this research developed a novel space bundle configuration of reinforced iron matrix composite using tungsten wire (W) and tungsten carbide (WC). This composite was prepared using a lost foam casting process combined with in-situ reaction. Microstructural analysis revealed that WC particles are distributed along the tungsten wire, with larger particles at the center and smaller ones at the edges. The formation of the reinforcement occurs in two stages: first, a solid-liquid reaction between the solid tungsten wire and molten iron during the lost foam casting process, promoting WC formation at high temperatures and carbon potential; second, an in situ solid-solid reaction where Fe diffuses and Fe3W3C decomposes, forming a composite structure of WC and α-Fe. The composite obtained at 1100°C for 9 hours exhibited a compressive strength of 836.59 MPa and a fracture strain of 18.69%, representing increases of 48.46% and 48.69% respectively compared to grey cast iron (GCI). The (W) WC/Fe bundle reinforcement effectively enhances the strength and toughness of the composite through the high volume fraction and gradient distribution of WC particles, combined with the synergistic effect of α-Fe. This research provides a new strategy for improving the mechanical properties of composite materials and resolving the issue of strength-toughness inversion.

Establishment of particle motion model and study of particle volume fraction distribution in the turbo air classifier based on DSMC

In order to study the particles' motion law and collision behavior in the flow field of the turbo air classifier, A particle motion simulation platform is developed using Compute Unified Device Architecture (CUDA) based on the Visual Studio. The particle-eddy interaction model, the particle-wall collision model, and the inter-particle collision Direct Simulation Monte Carlo (DSMC) solver are implemented. The results show that the deviation between calculated cut size d50 and experimental d50 using DSMC is smallest compared to DSMC, DDPM and DPM. DSMC has better acceleration performance compared to DDPM. The more particles need to be calculated, the more significant this advantage is. The influences of feeding rate on particle volume fractions and inter-particle collision number are analyzed. The increase of feeding rate leads to the increase of the particle volume fractions and inter-particle collision number.

An investigation of anisotropy in the bubbly turbulent flow via direct numerical simulations

We investigated the effects of bubble count, flow direction, and Eötvös number on deformable bubbles in turbulent channel flow. For a given shear Reynolds number Re = 180 and fixed bubble volume fractions (1.263% and 2.525%), we conducted a series of direct numerical simulations using a coupled level-set and volume-of-fluid solver to evaluate their impact on bubble volume fraction distribution, velocity fields, and turbulence characteristics. Each aspect was studied based on the microscopic equations of two-phase flow, and the accuracy of the modeling terms used in current Reynolds-averaged Navier–Stokes equation (RANS) models was assessed. The influence on the anisotropic state was analyzed using the Lumley triangle, and the anisotropy of Reynolds stresses was captured through the exact balance equations. The results indicate that in upward flow, bubbles tend to accumulate near the wall, with smaller Eötvös numbers leading to closer proximity to the wall and greater attenuation of the liquid-phase velocity. This distribution enhances energy dissipation and turbulence isotropy. In downward flow, bubbles cluster in the channel center, generating additional pseudo-turbulence and attenuating energy in the buffer layer. Moreover, the interfacial transfer of turbulent energy, as currently modeled in RANS, is found to be inadequate for upward flows.

Small Punch Testing of a Ti6Al4V Titanium Alloy and Simulations under Different Stress Triaxialities.

The mechanical properties of local materials subjected to various stress triaxialities were investigated via self-designed small punch tests and corresponding simulations, which were tailored to the geometry and notch forms of the samples. The finite element model was developed on the basis of the actual test method. After verifying the accuracy of the simulation, the stress, strain, and void volume fraction distributions of the Ti6Al4V titanium alloy under different stress states were compared and analyzed. The results indicate that the mechanical properties of the local material significantly differ during downward pressing depending on the geometric shape. A three-dimensional tensile stress state was observed in the center area, where the void volume fraction was greater than the fracture void volume fraction. The fracture morphology of the samples further confirmed the presence of different stress states. Specifically, the fracture morphology of the globular head samples (with or without U-shaped notches) predominantly featured dimples. Modifying the specimen's geometry effectively increased stress triaxiality, facilitating the determination of the material's constitutive relationship under varying stress states.

Study on Soot and NOx Formation Characteristics in Ammonia/Ethylene Laminar Co-Flow Diffusion Flame.

The formation of soot and NOx in ammonia/ethylene flames with varying ammonia ratios was investigated through experimental and numerical analysis. The spatial distribution of the soot volume fraction and NOx concentrations along the flame central line were measured, and the mechanism of soot and NOx formation during ammonia/ethylene co-combustion was analyzed using CHEMKIN 17.0. The experimental results indicated that the soot volume fraction decreases with an increase in ammonia ratio, with the soot peak concentration occurring in the upper region of the flame. The distribution of NOx is complex. In the initial part of the flame, a higher concentration of NOx is generated, and the lower the ammonia ratio, the higher the concentration of NOx. As the combustion process progresses, the concentration of NOx initially decreases and then subsequently increases rapidly, with higher ammonia ratios leading to higher concentrations of NOx. The addition of ammonia results in a decrease in CH3, C2H2, and C3H3, and an increase in CN concentration. This leads to a transformation of carbon atoms within the combustion system, reducing the available carbon for soot formation and suppressing its generation. A higher ammonia ratio increases the likelihood that NH3 will be oxidized to N2, as well as increasing the probability that any generated NO will undergo reduction to N2 through the action of the free radicals NH2 and NH.

Free vibration analysis of functionally graded composite plates reinforced with linearly and nonlinearly distributed carbon nanotubes in hygrothermal environments

This article presents a novel investigation of the free vibration behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates under hygrothermal environments. It explores both uniform and non-uniform (functionally graded) distributions of CNTs across the plate thickness for the first time. The effective material properties of the CNTRC, considering temperature and moisture dependence, are determined using the extended rule of mixture. First-order shear deformation theory (FSDT) is employed to derive the governing equations incorporating hygro-elastic and thermo-elastic relations. These equations are solved using the finite element method. A validation study verifies the accuracy of the employed approaches. Subsequently, a comprehensive parametric study investigates the influence of plate geometry (length-to-width and width-to-thickness ratios), CNTs volume fraction, boundary conditions, linear and non-linear CNTs distributions, and hygrothermal environments on the free vibration behavior of polymeric nanocomposite plates reinforced with CNTs fillers is conducted. The results reveal that the increase in temperature and moisture leads to a decrease in the effective stiffness of the FG-CNTRC plates.

Advanced ultrasound techniques for studying liquid–liquid dispersions in confined impinging jets

Advanced ultrasound techniques were used to study liquid–liquid dispersed flows formed in impinging jets confined in small channels. Ultrasound speed and attenuation coefficient spectra of the propagated sound waves were used to obtain volume fraction and drop size distributions, respectively. The results were compared against drop size distributions obtained with high-speed imaging. Experiments were conducted in a 2 mm internal diameter tube for both kerosene oil continuous and glycerol/water continuous dispersions. The overall mixture flow rate was set at 60 ml/s, and the dispersed phase fractions were 0.02, 0.05, and 0.10. The measured volume fractions were found to be very close to the input ones, indicating a very small slip between the phases in the dispersed flows. From the ultrasound measurements, the drop size distributions were found to range from 32 to 695 μm under the different conditions used. The drop sizes at the two low input volume fractions were in reasonable agreement with the results from the imaging. Imaging, however, could not be used for the 0.10 input dispersed phase fraction. These results demonstrate the applicability of the ultrasound techniques to measurements in dispersed liquid–liquid flows in small channels.

Vibrations in piezothermoelastic micro-/nanobeam with voids utilizing modified couple stress theory

The present study examines the vibrations in micro- and nano-piezothermoelastic beams with voids. In this work, the modified couple stress theory is employed to generate closed-form formulas for deflection, volume fraction, electric potential and temperature distribution. The effects of voids, modified couple stress, beam dimensions and electric potential on energy dissipation (thermoelastic damping) are examined for beams under various boundary conditions. We have established analytical formulas for frequency shift, attenuation and thermoelastic damping. MATLAB software is used to get numerical results and exhibit them visually.

Research on the Dynamic Softening Mechanism of Dual‐Phase Structure During Warm Forming of Fe–8.5Mn–1.5Al Medium‐Manganese Steel

In this article, Fe–8.5Mn–1.5Al medium‐manganese steel is taken as the research object, and Gleeble 3500 thermal simulation testing machine is used to conduct isothermal compression at different deformation temperatures, strain rates, and strains in its austenite ferrite two‐phase zone. A constitutive model and a dynamic recrystallization volume fraction model for materials are established, and finite‐element method is used to simulate the temperature, equivalent strain, and dynamic recrystallization volume fraction distribution in different regions of the workpiece under different deformation conditions. By comparing and analyzing the microstructure, finite‐element simulation results, and hot working diagrams obtained from the experiment, the microscopic mechanism of dynamic softening of the material when ferrite and austenite coexist is explained; the transformation of the dynamic softening mechanism of the two phases with the hot deformation process is also explained. Early deformation mainly occurs in softer ferrite, which preferentially undergoes continuous dynamic recrystallization. Austenite has a lower stacking fault energy, and discontinuous dynamic recrystallization (DDRX) occurs when the dislocation density reaches a certain critical value. At the same time, when the strain reaches a certain level, the dynamic softening behavior of ferrite will also transform into DDRX. The optimal deformation conditions for Fe–8.5Mn–1.5Al medium‐manganese steel during warm processing in the two‐phase zone are a temperature of 720 °C, a strain rate of 0.01 s−1, and a large deformation zone.

A scale-span method to characterize the mechanical property of BCF/PEEK considering uncertain structural characteristics

The focus of this study is exploring a scale-span characterization method to predict the mechanical properties of Braided Carbon Fiber Reinforced Poly Ether Ether Ketone (BCF/PEEK) considering structural uncertainty. Firstly, a complicated micro-scale Representative Volume Element (RVE) model that considers the random position and size of fiber was established via the developed Python script. Analogously, a mathematical expression adopted by the trust region algorithm was proposed to accurately describe the detailed cross-sectional shapes and fluctuation amplitude characteristics of BCF/PEEK for the sake of establishing the precision meso-scale RVE model. Then, the corresponding elastic properties that consider fiber volume fraction and fiber distribution location were characterized via the span-scale characterization method. Meanwhile, the influence of fiber bundle fluctuation amplitude and fiber volume fraction on the mechanical properties was investigated as well. In addition, the mechanical properties of BCF/PEEK with the change of the braid angle between warp and weft yarn were predicted via the established meso-scale RVE model. Finally, a series of experiments have been carried out. The maximum and minimum absolute prediction deviation of all elastic property parameters were only 4.07 % and 1.41 %, respectively, which verified the proposed scale-span characterization method can predict the mechanical properties of composites well.

Investigation of the Defect Effects on the Load-Carrying Capacity of Butt Joints: A Numerical Study

Determining the behavior of joints under a specific load and estimating the damage potential is essential for ensuring the durability of joints in engineering structures. Defects might occur at the adhesive layer, which causes a reduction in the durability of joints. This work aims to examine the effects of the defect presence, defect volume fraction, defect position, and random distribution of defects at the adhesive layer on the durability of the butt joint. A finite element (FE) model of the butt joint was constructed using the commercially available FE software Abaqus/Standard. The validation of the FE model was conducted by comparing its results with experimental finding reported in existing literature. Numerical and experimental results showed strong agreement, with relative errors of 2.46% and 2.95% at peak force and displacement at peak force, respectively. Defect presence significantly influences the durability of the butt joint. Defect volume fraction and defect location are the dominant parameters affecting the durability of the butt joint. The square defects at the center of the bonding layer, with volume fractions of 0.05, 0.10, and 0.15, lowers the peak force by 5.08%, 10.56%, and 15.73%, respectively. When the defect is positioned at the center of the bonding layer, adhesive failure starts at the edges of the defects. However, relocating the defect from the center to the left or upper side of the bonding layer results in adhesive failure initiation at the corresponding edges of the adhesive. Random defect distribution in the adhesive layer doesn’t affect joint durability.

Numerical optimization of volume fraction distributions in FGM sandwich beams with FG-CNTRC facesheets

Numerical optimization of volume fraction distributions in FGM sandwich beams with FG-CNTRC facesheets

Three-Dimensional Modeling of Anion Exchange Membrane Electrolysis: A Two-Phase Flow Approach

Anion exchange membrane water electrolyzers (AEMWEs) are attracting growing interest as a green hydrogen production technology. Unlike proton exchange membrane (PEM) systems, AEMWEs operate in an alkaline environment, allowing one to use less expensive, non-noble materials as catalysts for the reactions and non-fluorinated anion exchange polymer membranes. However, the performance and stability of AEMWEs strongly depend on the alkaline electrolyte concentration. In this work, a three-dimensional multi-physics model considering two-phase flow effects is applied to understand the impact of KOH electrolyte concentration and its flow rate on AEMWE performance, as well as on the current and gas volume fraction distributions. The numerical results were compared to experimental data published in the literature. For current densities above 1 A/cm2, a strongly non-uniform H2 and O2 gas volume distribution could be evidenced by the 3D simulations. Increasing the KOH electrolyte flow rate from 10 to 100 mL/min noticeably improves cell performance for current densities above 1 A/cm2. These results show the importance of accounting for the three-dimensional geometry of an AEMWE and two-phase flow effects to accurately describe its operation and performance.

Experimental and numerical investigations of soot formation in propane laminar coflow flames in O2/N2 and O2/CO2 atmospheres

Oxygen-rich combustion is a new type of clean combustion technology with important application prospects. At present, there are few detailed analyses on the mechanism changes of soot formation under oxygen enrichment of propane. In this paper, the effects of oxygen-rich (O2/N2, O2/CO2) combustion on soot formation in the propane laminar flow coaxial jet diffusion flame were investigated by using the experiment and numerical simulation. The flame image was taken by a color (CCD) camera in the visible band, and the two-dimensional distribution of temperature and soot volume fraction in the flame was reconstructed. In numerical simulation, the soot production model considers a detailed description of nucleation via collisions among heavy polycyclic aromatic hydrocarbons, particle aggregation, polycyclic aromatic hydrocarbons condensation, surface growth and oxidation through the hydrogen abstraction acetylene addition mechanism. The results show that the experimental results were compared with the numerical simulation results, and the numerical simulation results predict the temperature and soot change of oxygen-rich flame well. With the increase in oxygen concentration, the peaks of soot and temperature in the two oxygen-rich atmospheres gradually increased. With the increase in oxygen concentration, the peaks of soot and temperature in the two oxygen-rich atmospheres gradually increased. Comparing the combustion mechanism changes of the two oxygen-rich combustion systems, it was found that the hydrogen abstraction acetylene addition mechanism was the main cause of soot generation. The OH oxidation is dominated near the fuel nozzle side, and O2 oxidation is dominant downstream. With the substitution of CO2 for N2, the chemical effect of CO2 reduces the flame temperature and inhibits the formation mechanism and oxidation mechanism of soot to some extent. This in turn leaded to a reduction in the amount of soot produced.