Dimensionless Factor Research Articles

Investigation of heat transfer performance and enhancement mechanisms of supercritical carbon dioxide in PCHE with fractal airfoil fins

A fractal structure featuring symmetric/asymmetric airfoil fins is embedded within the smooth channels of the printed circuit heat exchanger (PCHE), significantly enhancing its heat transfer performance. In this study, a horizontally installed two-layer channel configuration is examined, with hot CO2 flowing through the upper channel and cold CO2 through the lower channel. Two distinct airfoil fin designs, namely NACA 0021 symmetric and NACA 4822 asymmetric, are tested for their channel reinforcement effect. The numerical analysis reveals that channels equipped with these fins exhibit substantially improved heat transfer compared to smooth channels. Notably, the comprehensive evaluation index for the asymmetric airfoil fin channel is enhanced by a factor ranging from 1.05 to 3.76. Moreover, despite a modest increase in pressure drop, indicated by a dimensionless friction factor of 0.67–1.31, the heat transfer performance remains superior. Crucially, optimal heat transfer does not rely solely on high fluid flow rates but instead demands an apt flow matching between the hot and cold fluid channels.

Modeling of Granulation in Red Supergiants in the Magellanic Clouds with the Gaussian Process Regressions

The granulation of red supergiants (RSGs) in the Magellanic Clouds is systematically investigated by combining the latest RSG samples and light curves from the Optical Gravitational Lensing Experiment and the All-Sky Automated Survey for Supernovae. The present RSG samples are first examined for foreground stars and possible misidentified sources, and the light curves are sequentially checked to remove the outliers by white noise and photometric quality. The Gaussian process (GP) regression is used to model the granulation, and the Markov Chain Monte Carlo is applied to derive the granulation amplitude σ and the period of the undamped oscillator ρ, as well as the damping timescale τ. The dimensionless quality factor Q is then calculated through Q = π τ/ρ. RSGs around Q=1/2 are considered to have significant granulation signals and are used for further analysis. Combining granulation parameters with stellar parameters, robust scaling relations for the timescale ρ are established, while the scaling relations for amplitude σ are represented by a piecewise function, possibly related to the tendency of amplitudes in faint RSGs to converge toward a certain value. Comparing results between the Small Magellanic Cloud and the Large Magellanic Cloud confirms that amplitudes and timescales become larger with metallicity. In examining the scaling relations between the two galaxies, it is found that ρ is nearly independent of metallicity, whereas σ is more significantly affected by metallicity. The GP method is compared with the periodogram fitting of the granulations, and the advantages of either are discussed.

Experimental Study on Fracture Toughness of Shale Based on Three-Point Bending Semi-Circular Disk Samples

A large number of construction practice projects have found that there are many joints and microcracks in rock, concrete, and other structures, which cause the complexity of rock mechanical properties and are the main cause of geological or engineering disasters such as earthquakes, landslides, and rock bursts. To establish a rock fracture toughness evaluation method and understand the distribution range of fracture toughness of Longmaxi Formation shale, this study prepared three-point bending semi-circular disk shale samples of Longmaxi Formation with different crack inclination angles. The dimensionless fracture parameters of the samples, including the dimensionless stress intensity factors of type I, type II, and T-stress, were calibrated using the finite element method. Then, the peak load of the samples was tested using quasi-static loading, and the load–displacement curve characteristics of Longmaxi Formation shale and the variation in fracture toughness with crack inclination angle were analyzed. The study concluded that the specimens exhibited significant brittle failure characteristics and that the stress intensity factor is not the sole parameter controlling crack propagation in rock materials. With an increase in crack inclination angle, the prefabricated crack propagation gradually transitions from being dominated by type I fracture to type II fracture, and the T-stress changes from negative to positive, gradually increasing its influence on the fracture. An excessively large relative crack length increases the error in fracture toughness test results. Therefore, this paper suggests that the relative crack length a/R should be between 0.2 and 0.6. The fracture load distribution range of shale samples with different crack angles is 3.27 kN to 10.92 kN. As the crack inclination angle increases, the maximum load that the semi-circular disk shale samples can bear gradually increases. The pure type I fracture toughness of Longmaxi Formation shale is 1.13–1.38 MPa·m1/2, the pure type II fracture toughness is 0.55–0.62 MPa·m1/2, and the T-stress variation range of shale samples with different inclination angles is −0.49–9.48 MPa.

Comparison on thermal and hydraulic performances of transverse mini-channel based on a novel comprehensive evaluation factor

To disclose the application value of cold plate with transverse layout used in thermal management system, a novel dimensionless factor, Comprehensive Index of Thermal Management System (CITMS), is proposed, which involves three most important parameters: pumping power Etol, temperature dispersion Tσ and maximum temperature Tmax. Results show that compared to 15 types of mini-channels (longitudinal parallel, serpentine, bifurcated, u-turn, annular, zigzag, cobweb, elm leaf, diverged, rhombus spoiler, gridding, wave, honeycomb, multistage tesla-valve, pease types), transverse parallel mini-channel shows superior CITMS, which declines by an average of 80.26 % to 99.61 % under weighting coefficient w = 1 and expected operating temperature Texp = 320.15 K. Meanwhile, zigzag, wave, pease and multistage tesla-valve mini-channels with transverse layout show significantly better CITMS than longitudinal layout, which decline by an average of 78.61 % to 89.03 %. This is mainly due to the decline in Tσ and Etol. Furthermore, based on CITMS, an appropriate mass flow rate can be achieved for a specific cold plate. Under w = 30 and Texp = 298.15 K, the optimal value of CITMS for transverse parallel mini-channel occurs at 0.5 g/s. In view of better comprehensive performance and same process difficulty, transverse layout could undoubtedly become an effective design concept.

Effect of microbial growth and electron competition on nitrous oxide source and sink function of hyporheic zones

The hyporheic zones (HZs) are key sites of the production of nitrous oxide (N2O), a potent ozone-depleting greenhouse gas. Denitrification is the primary process of N2O production in HZs, including four reduction steps (NO3−→NO2−→NO→N2O→N2). Electron competition occurs between the four reduction steps and can significantly impact the production of N2O. However, denitrification was typically considered as simplified two step reactions for investigating the release of N2O, neglecting the electron competition among the four-step reactions. Moreover, the N2O production/consumption patterns are regulated by both hydraulic and biogeochemical conditions in HZs. Dynamic microbial growth cannot only mediate the biogeochemical reactions, but also change hydraulic properties spatiotemporally by bioclogging. But microbial growth is rarely considered for investigating N2O dynamics of HZs. To assess these effects on hyporheic N2O dynamics and source-sink function, we establish a novel numerical model of N2O dynamics of HZs, coupling porous flow, reactive transport, electron competition, microbial growth and bioclogging. The results show that the weak electron competitiveness of N2O reductase results in a less allocation of electrons to the N2O reduction process, particularly in situations with limited carbon sources, thus increasing the release of N2O into the rives. Microbial growth significantly influences N2O release from HZs into rivers, increasing by more than two orders of magnitude on average compared to the model neglecting microbial dynamics. In contrast to the classical knowledges that HZs in coarse sediments tending to short residence time cannot act as sources of N2O, dynamic microbial growth obviously increases the potential for N2O release from HZs in coarse sediments to the rivers. The global Monte Carlo regional sensitivity analyses indicate that microbial biomass is the most critical factor determined the hyporheic source-sink function for N2O, followed by carbon oxidation rate and residence time. These are significantly different from previous knowledge that the residence time and oxygen/nitrogen uptake rate are the most sensitive parameters, which may lead to misunderstanding of the key controlling factors of N2O release from HZs. In addition, we propose a new Damköhler number (DaO2∗) of dissolved oxygen by multiplying the classical DaO2 with a dimensionless microbial modification factor for identifying N2O source-sink function of HZs, with DaO2∗ < 1 for N2O sink, while DaO2∗ > 1 for N2O source.

Electric-field activating on-surface tailored (OST) coarse polyester fibers for efficient airborne particle removal: Interfacial morphologies and electrical response

Fibrous filtration is the most-used method for indoor particulate matter (PM) removal. The filtration performances are governed by filters’ intrinsic geometries, displaying the tradeoff among efficiency, resistance, and lifespan. In this contribution, we provided a chemically-synthesized strategy to improve the performance of coarse filters while preserving their ultralow initial resistances. After elucidating PM-fiber interactions, the fibrous interfacial nano-morphologies were tailored by different dielectric coatings based on commercially-available substrates. Activated by fiber polarizing, the tuned morphologies with ∼100 nm surface roughness and enhanced electrostatic potential are considered the drivers of boosted filtration efficiency. In practice, a 10-mm-thick polydopamine (PDA)-MnOx coated polyester filter possessed an improved efficiency of 97.7 % for 300–500 nm particles, and the ultralow resistance of 11.2 Pa at 0.5 m/s filtration velocity. The strong surface adhesion facilitated long-term efficiency of 95.6 % in a continuous 25-day period without any decay. The nanoscale coatings, which were just one-thousandth in thickness of the fiber gaps, enabled more than 50-fold improvement of the filters’ quality factor. We further established dimensionless factors to evaluate the cost-performance effect. We expect the strategy and techniques can pave the way to better understand electrostatic air filtration, being competitive candidates in the air filtration community.

Analytical analysis of the interaction between cavities and a crack in bonded isotropic and anisotropic half spaces under SH wave

Interaction between two cavities and a linear crack subjected to elastic shear horizontally (SH) wave is investigated analytically in this work. Two cavities are buried in two bounded half spaces respectively and the cross-section of each cavity has a different shape. The media of two half spaces are isotropic and anisotropic respectively, and the complex function method is applied to first solve the wave equation in each medium. Then, with the help of image principle, Green’s functions and wave field expressions in each separated half space are constructed. Subsequently, utilizing “conjunction” technique, a series of Fredholm integral equations containing undetermined forces at the interface are obtained and reduced in order to be solved. Dynamic stress distribution is mainly considered to discuss the interaction between the cavities and the crack. Finally, a parametric study on dynamic stress concentration factor (DSCF) and dynamic stress intensity factor (DSIF) presents the interaction is affected by several dimensionless factors simultaneously.

Quantitative description of the quality of size exclusion chromatography separations

Size exclusion chromatography (SEC) is unique among chromatographic methods as it allows separation of non-retained analytes. However, such mechanism often put an analytical scientist in front of relatively poorly resolved set of peaks that may have strikingly different abundance. The description of such chromatograms needs a particular approach to accurately capture the overall quality of separation. Consequently, use of a single parameter description may not be accurate enough and therefore we introduce a dimensionless separation quality factor, which is based on five SEC specific measures (peak-to-valley, elution window width, peak widths, peak-positioning and recovery). Combining several factors allowed detailed differentiation of various simulated separations, clearly correlating column characteristics with specific contributions to separation quality whether they concern a single peak pair or entire peak landscape. The method could be further elaborated by the addition of normalized priority weighting allowing for flexible quality quantification of a relevant portion of real-life nucleic acid separation on different columns. With growing complexity of biotherapeutics to be separated, such a term is predicted to be a useful response function for purposes of factorial method optimization.

Non-similar simulations of Ellis model based ternary hybrid nanofluid flow through porous media

The investigation of nanofluid flow through porous media is an emerging area of research in the optimization of thermal processing and numerous thermodynamic processes. The principal objective of these thermal applications is to examine the movement of ternary hybrid nanofluid across a stretched sheet oriented vertically. The flow being examined is represented mathematically in order to incorporate the influences of magnetic fields, thermal radiation, and viscous dissipation. The ternary hybrid nanofluid thermal performance can be enhanced and surpassed by adding nanoparticles to the base fluid. The non-Newtonian Ellis model takes into account the fluid movement through the porous media. Ferrous oxide ( Fe 3 O 4 ) , Zinc oxide ( ZnO ) , and Molybdenum disulfide ( Mo S 2 ) are regarded as nanoparticles, with ethylene glycol ( EG ) serving as the base fluid. To convert the governing equations into a dimensionless system, suitable non-similar transformations have been established. The local non-similarity (LNS) approach is used with the MATLAB built-in tool bvp4c up to the second truncation level. The physical impacts of dimensionless factors on the temperature and velocity profiles of the studied nanofluids are thoroughly investigated. When the magnetic and porosity parameters change, the velocity profile becomes smaller. The heat transmission rate declines when the assessments of the magnetic number and Eckert number increase. The skin friction coefficient experiences an increase as the estimates of magnetic properties and nanoparticle value rise. The current study holds various practical implications, encompassing Solar Thermal Energy Storage, Waste Heat Recovery, Advanced Cooling Technologies, Enhanced Geothermal Systems, and Enhanced Oil Recovery.

On inherent hyperelastic crease

We present analyses of the inherent hyperelastic crease that entails an unstable degenerative singular perturbation field over a uniformly compressed hyperelastic half-space. The analyses reveal asymptotic far-field characteristics of the singular field that bring out admissible incremental elastic deformation mechanisms of the inherent creasing instability typically observed at a compressive strain of ∼0.354 in neo-Hookean solids. The admissible singular perturbation field has an asymptotic leading-order incremental-stress singularity decaying 1/r2 as the distance from the crease tip r→∞. In general, asymptotic incremental-deformation fields of 1/r2 stress singularity can be introduced by surface flaws. We found that the singular field creates a far-field eigenmode of three energy-release angular sectors separated by two energy-elevating sectors of incremental deformation. The far-field eigenmode braces the near-tip energy-release field of the surface flaw against the transition to an unstable self-similar expansion field of creasing. Two asymptotic far-field parameters can characterize the braced-incremental-deformation (bid) and crease fields. One is the Burgers vector of a projected subsurface dislocation of the asymptotically singular far field. The other is a dimensionless shape factor representing the ratio of the subsurface depth of the dislocation to the Burgers vector. Our analyses show that the shape factor gauges the transition from the stable bid field to the unstable inherent crease field at the crease limit point as the compression increases. Two tangential-manifold conservation integrals are revealed to identify the two parameters. At the crease-limit point, matched asymptotes lead to the ratio between the two separate scaling parameters of the asymptotic solutions of the crease-tip folding field and the leading-order far field. To this end, we introduced a novel finite element method (FEM) for simulating the crease field nearly in a hyperelastic half-space with a finite-size simulation domain. Furthermore, we uncovered with the Gent model (1996) that strain-stiffening in hyperelasticity alters the dependence of the shape factor on the compressive strain, raising crease resistance. The new findings in hyperelastic crease mechanisms will help study ruga mechanics of self-organization and design soft-material structures and skin conditions for high crease resistance.

Entropy generation on the dynamics of volume fraction of nano-particles and coriolis force impacts on mixed convective nanofluid flow with significant magnetic effect

Recent advances in simulating entropy generation for dissipative cross-materials with a quartic auto catalyst are reported. Entropy generation can be used to generate entropy in any irreversible heat transfer process, which is important in thermal machines. This study examines the impact of entropy generation on the thermal transport and momentum of a continuous two-dimensional dusty fluid magnetohydrodynamic (MHD) migration across an inclined stretched sheet. We also conducted an entropy generation study to discuss the effects of viscous dissipation, the volume proportion of dust particles, and mixed convection. The two-phase models that address the fluid phase and the solid phase have been discussed. As part of the flow model’s innovation, the effect of raising particulate matter concentration on the dynamic behavior of the fluid is investigated. The described model transforms the prevailing partial differential equations (PDEs) for two phases into a nonlinearly associated, nondimensional set of equations by implementing appropriate similarity alterations. For graphical results, MATLAB programming incorporates the bvp4c mechanism. This study indicates how to examine the impact of appropriate factors on the dusty phase of fluid and the non-Newtonian fluid phase. Both the entropy generation ( E gen ) and the Bejan quantity (Be) are presented in relation to their associated dimensionless factors. Parametric research is used to evaluate the impact of different flow parameters on temperatures, entropy generation, and Bejan numbers. The heat transfer rate using several quadratic regression models, which provide more clarity in determining physical parameters crucial to engineering, is assessed. It is observed that the entropy ( E gen ) and Bejan number (Be) declines with the rising mass concentration ( β ν ) of dusty particles. Also demonstrated that for both cases, increasing the magnetic influence and dust volume fraction ( Φ D ) resulted in a decrease in velocity profiles at the same time as temperature increased.

Degree of bending of FRP-reinforced tubular X-joints in offshore jacket-type structures under in-plane bending moment

In offshore jacket structures, the stress within the chord thickness of tubular joints arises from both membrane and bending stresses. The Degree of Bending (DoB)—the ratio of bending stress to the total stress—is key to evaluating these joints' fatigue resistance. This study delves into the DoB in tubular X-joints reinforced with fiber-reinforced polymer (FRP) subjected to in-plane bending moment. It begins by validating finite element (FE) analysis accuracy through comparison with existing theoretical and experimental evidence. Following this, the analysis of 166 joints was conducted to examine how variations in FRP characteristics (such as type, layer count, and layout) and the joints' dimensionless geometric factors influence the DoB and its ratio in reinforced joints compared to their unreinforced counterparts. Findings indicate that FRP layers enhance fatigue resistance by lowering hot spot stresses on the chord's inner and outer surfaces and elevating the DoB value by up to 26.16%. Consequently, the study introduces a parametric formula for calculating the DoB in FRP-reinforced tubular X-joints under an in-plane bending moment. This development is significant, as there was no existing parametric formula for determining DoB in FRP-reinforced joints. The proposed formula stands out for its high determination coefficient and minimal error, effectively addressing a notable gap in the field.

Determining the optimal dome shape using a novel variable slippage coefficient non‐geodesic

AbstractThe research of high‐performance composite pressure vessels in practical application has become the focus of attention, and fiber paths play an important role in the structural performance of composite pressure vessels. Therefore, a method is proposed for determining the optimal geometric parameters of the pressure vessel head shape under a novel variable slippage coefficient non‐geodesic(NVSCNG). First, NVSCNG is used as the dome fiber path design mode, and the classical lamination theory is used to construct a dome stress field model. In addition, on the basis of the Tsai‐Wu failure criterion, the minimum laminate thickness is determined to satisfy the strength constraints. Second, the performance factor (pressure*volume/weight) is used to calculate the structural performance of the dome with variable geometric parameters under the novel variable slippage coefficient fiber path. Moreover, the stability constraints are considered to determine the optimal geometric parameter values of the dome. Finally, the structural properties, stress response and thickness were analyzed under two types of fiber paths based on the optimal dome profile. Results show that compared to the conventional variable slippage coefficient, the performance factor can be maximally improved by nearly 60.94% using the novel variable slippage coefficient, and the thickness of the composite layer at the equator of the dome can be maximally reduced by nearly 34.88%. In addition, the research shows that NVSCNG can improve the structural performance of the dome and realize the lightweight of dome components, which are greatly important in guiding the design of fiber paths for pressure vessels.Highlights No unconstrained linear problem between NVSCNG and initial winding angle. Optimal dome profile geometry parameters are m = 0.8, rc = 0.5. The dome structural failure is controlled by the longitudinal stresses. Winding angle distribution has a strong influence on dome stress distribution. Higher dimensionless performance factor and lighter mass for NVSCNG.

Experimental investigation of metal foam embedded surface thermal characteristics using air-jet impingement with different orifice geometry

Experimental investigation of metal foam embedded surface thermal characteristics using air-jet impingement with different orifice geometry

Sodium alginate-based MHD ternary nanofluid flow across a cone and wedge with exothermic/endothermic chemical reactions: A numerical study

The use of magnetohydrodynamic ternary nanofluid flow for heat transfer is essential in various industrial and commercial applications. This work examines heat transfer over cone and wedge shapes with Sodium Alginate-based ternary nanofluid flow, considering the effects of activation energy and exothermic/endothermic processes. Using similarity transformations, the controlling set of partial differential equations is converted into a network of interconnected nonlinear ordinary differential equations. Numerical solutions using the Runge-Kutta Fehlberg 4th 5th order method and shooting approach offer insights into the effects of several dimensionless factors. The outcomes show that the magnetic field parameter is crucial in lowering fluid velocity within a cone more efficiently than a wedge. Due to activation energy considerations, the cone shape notably impacts heat transmission in exothermic reactions, but the wedge geometry is more effective in endothermic reactions. Concentration profiles rise with activation energy and fall with increasing chemical reaction rates. The rate of thermal distribution is 48.68% more in wedge than cone geometry for the exothermic case and 35.57% in the endothermic case while the rate of mass transfer is higher in cone geometry than wedge geometry, about 7.83% in the exothermic case and 19.27% in the endothermic case. The present study has many applications, including optimizing heat transfer processes in sectors such as thermal systems, energy generation, and electronics. Additionally, it may be used to guide the design of magnetically affected systems and provide assistance for uses in chemical engineering.

Effect of Double Stratification on MHD Williamson Boundary Layer Flow and Heat Transfer across a Shrinking/Stretching Sheet Immersed in a Porous Medium

The present study aims to provide a mathematical model of the Williamson fluid flow via a permeable stretching/shrinking sheet in the MHD boundary layer in the presence of a heat source, chemical reaction, and suction. This study is novel because it investigates the physical effects of thermal and solutal stratification on convective heat and mass transport using thermal radiation. The flow’s PDEs are numerically solved using the BVP4c approach and the pertinent similarity variables until a stable solution is found. Through visual analysis, the effects of dimensionless factors on temperature, velocity, and concentration profiles are examined. This encompasses the mass transfer rate, the heat transfer rate, and the coefficient of friction. The results of the present analysis are found to be consistent with those of previously published studies. The findings demonstrate that enhanced temperature and concentration profiles cause the Williamson, magnetic, and permeability parameters to rise in conjunction with a drop in the dimensionless velocity. In relation to temperature, the thermal stratification parameter exhibits the opposite tendency. Regarding the solutal stratification parameter, concentration profiles are seen to show the opposite trend. Lastly, the current work will have important implications for the removal of dust and viruses from viscoelastic fluid in bioengineering, the medical sciences, and medical equipment.

Using deep learning method to predict dimensionless values of stress intensity factors and T‐stress of edge notch disk bend (ENDB) specimen

AbstractA deep learning (DL) approach is implemented to determine the dimensionless stress intensity factors of mode‐I (YI) and mode‐III (YIII), as well as the normalized T‐stress (T*) of the edge notch disk bend specimen. The deep neural network (DNN) method as the DL approach is used to model the relationship between the geometry parameters of the specimen a/t, S/R, and β as inputs, and YI, YIII, and T* as output variables. To this end, three datasets consisting of 176, 176, and 123 finite element method data points from the previous studies are extracted for YI, YIII, and T*, respectively. The developed DNN models predicted the YI, YIII, and T* with correlations of 0.97003, 0.96918, and 0.97047, respectively. Then partial dependence plot is performed to determine the relationship between YI, YIII, and T* and the geometry parameters, which is useful in predicting and optimizing YI, YIII, and T*.

Experimental and model research on judging liquid accumulation in pipelines under the action of surfactant

Foam drainage gas extraction is applied in various natural gas extraction scenarios, such as water-bearing gas wells, gas fields with high water content, and wet natural gas pipeline transport, with the goal of enhancing extraction efficiency and lowering production costs. A common issue in foam-carrying liquid gas wells and wet natural gas pipelines is the large errors observed in the prediction model for liquid accumulation onset, derived using ellipsoidal droplets. Additionally, this model is only applicable to a single surfactant type and concentration. To investigate the effects of different types and concentrations of surfactants on the onset of liquid accumulation. This paper re-establishes the critical foam-carrying flow rate model for spherical cap-shaped foam droplets using Newton's laws of motion, through an analysis of their motion state within the air core. Through the critical foam-carrying flow rate test experiments and foam droplet deformation test experiments to obtain critical foam-carrying flow rate model in the surface tension, foam density, Weber number, drag coefficient and other parameters of the change rule and calculation method. The model's validity was further confirmed using field-measured production data from foam-carrying liquid gas wells, demonstrating accurate validation results. Compared to the previous model, this new model treats foam droplets as spherical cap-shape and introduces a dimensionless scaling factor and foaming capacity to quantify the impact of surfactant types and concentrations on foam droplet surface tension and density. This enhances the model's applicability across different types and concentrations of surfactants with greater accuracy. This offers an efficient, precise, and versatile method for predicting liquid accumulation in foam-carrying liquid gas fields, thereby enhancing the efficiency and safety of gas extraction.

Time-dependent concrete chloride diffusion coupled with nonlinear chloride binding: An analytical study

Both the temporal dependence of chloride diffusion coefficient and the effect of nonlinear chloride binding substantially affect the behavior of concrete chloride diffusion. This study develops an exact chloride diffusion solution that accommodates the above two factors by introducing a simplified but reasonably realistic nonlinear chloride binding isotherm. The introduction of this isotherm makes it possible to achieve an analytical solution to a highly nonlinear chloride diffusion equation that involves a free chloride concentration dependent dimensionless factor which reflects the effect of chloride binding. First, a time-dependent chloride diffusion model incorporating the introduced isotherm is established with the corresponding exact solution derived. The proposed solution is successfully validated against two existing analytical solutions and a numerical solution. Parametric study is conducted using the proposed solution to investigate how the parameters regarding chloride ingress influence the corrosion initiation time, and results show that the increase of the initial effective chloride diffusivity or the before-ingress age decreases the corrosion initiation time bringing an acceleration of a different level to chloride diffusion while the increase of the age factor prolongs the corrosion initiation time decelerating chloride diffusion to some extent, and as each of the three nonlinear chloride binding associated parameters (i.e., the deflection-point concentration, the former slope and the latter slope) increases, the corrosion initiation time rises and the retardation effect on chloride diffusion is enhanced to a various extent. Lastly, to demonstrate the practical validity of the proposed solution, the solution is applied to reproducing a reported chloride diffusion test, and it turns out that our solution reproduces the diffusion test reasonably well, justifying its practical validity.

Boundary effect of foamed cement paste under the influence of air-coupled impact-echo

The air-coupled impact-echo method has been increasingly utilized for the detection of cement-based materials. In this study, an air-coupled impact-echo system is developed. This system evaluates the response of cast-in-place foamed cement paste blocks subjected to air-coupled impact-echo. The shape factor is calculated based on the acquired impact-echo spectrograms to analyze the boundary effects of the blocks. The results show that the values of the shape factor vary with the impact location, as the impact location from the edges of the blocks affects the air-coupled impact-echo response. Accordingly, a dimensionless factor is proposed to evaluate the boundary effect of block-like foamed cement paste. This study contributes to the application of the air-coupled impact-echo method for the detection of foam cement paste.