Mean Concentration Profiles Research Articles

Transient dispersion of reactive solute transport in electrokinetic microchannel flow

Motivated by emerging applications in bio-microfluidic devices, the present study rigorously examines the generalized Taylor–Gill hydrodynamic dispersion of a point source solute injected into a microchannel, influenced by a constant axial static electric field along the channel and charged surface with different wall potentials. The solute engages in a first-order irreversible chemical reaction at both the microchannel walls. By incorporating different wall potentials and absorptive coefficients at the lower and upper walls, the current transport model for electro-osmotic flows is extended to encompass a wider range of applications. The solute transport phenomenon is intricately modeled using the unsteady convective diffusion equation. Employing Gill's generalized dispersion model, a concentration decomposition technique, up to the third-order accuracy, we meticulously analyze the transport process. Furthermore, a comprehensive comparison between analytical outcomes and numerical simulations using the Brownian Dynamics method is undertaken, enhancing the robustness of the analytical approach. The scattering process is mainly analyzed with the help of exchange, convection, dispersion, and asymmetry coefficients, along with the mean concentration profile. The effect of initial solute release at various vertical locations in the microchannel is shown to exert a considerable impact on all the transport coefficients at initial times.

Drag reduction by natural yam mucilage in turbulent flows

Nontoxic bio-polymeric drag reducers are of great practical importance. In this work, a new natural and environmentally friendly drag reducer is introduced, which is extracted from the yam. Yam mucilage solutions are highly shear thinning and are insensitive to temperature variation. Their drag-reducing capability is tested in a water tunnel with the injection of yam mucilage solutions at the bottom wall. The main flow speed varies 0.5–2 m/s, and the corresponding bulk Reynolds number (Re) varied from 11 467 to 45 868. The mean concentration profile from the planar laser-induced fluorescence (PLIF) images and the mean velocity profile from the particle image velocimetry (PIV) images are obtained to explain the drag reduction of the yam mucilage solution. A maximum drag-reduction rate (DR) of 25.27% is achieved. The effects of the solution concentration, the injection rate, and the main flow speed on the drag-reduction efficiency are explored. The DR-log10K fitting curve is linear, consistent with that of the reported polymer drag reducers. The K-scaling laws also imply that the consumption of yam mucilage would be much more than that of polyethylene oxide (PEO) corresponding to similar DR. The further revelation of the effective drag-reducing component within the yam mucilage is believed to promote the efficiency of drag reduction. The yam mucilage is a candidate drag-reducing agent that can be an alternative to existing polymer solutions.

Molecular simulation of CO2 capturing by dual functionalized phosphonium-based amino acid ionic liquids

Various solvents have been proposed considering the importance of CO2 gas removal from the environment. Over the past few decades, ionic liquids (ILs) have elicited much attention due to their unique properties. In this regard, capturing the CO2 gas by phosphonium-based amino acid ILs (AAILs) was studied by molecular dynamics (MD) simulation. The effect of cation functionalization was studied. The anion was glycinate, [GLY]-, and the cation was tetrabutylphosphonium, [P4444]+, functionalized by different functional groups including acidic (−COOH), alcoholic (−OH), amine (−ΝΗ2), and ether (−OCH3). Density, absorption energy, radial distribution function (RDF), mean square displacement (MSD), concentration profile, free volume, and fractional free volume were under investigation. According to density values calculated from MD simulation, functionalized AAIL with a carboxylic acid group ([P4444COOH][Gly]) is the most concentrated system with the maximum interaction energy between AAIL and the trapped CO2 gas equal to − 1.917 kcal.mol−1. In addition, the lowest volume variation was observed through this physical absorption. RDF analysis reveals that anion interaction with CO2 gas is the most considerable one in the case of [P4444COOH][Gly] AAIL. The CO2 uptake is 2:1 for functionalized AAILs that shows cation functionalization improves CO2 gas absorption capacity; each mole of [P4444COOH][Gly] AAIL is capable of surrounding 2.11 mol of CO2. Finally, the gas diffusion coefficient is the lowest one in [P4444COOH][Gly] AAIL as the solvent-free volume is observed as a continuous channel to trap CO2 gas with the lowest gas diffusivity parameter.

Significance of skewness and kurtosis on the solute dispersion in pulsatile Carreau–Yasuda fluid flow in a tube with wall absorption

Solute dispersion in Carreau–Yasuda fluid flow in a tube presented in Rana & Murthy (Proc. R. Soc. Lond.A, vol. 472, 2016, p. 20160294) was limited to a steady-state velocity profile due to the nonlinearity associated with the Yasuda parameter$a$with power-law exponent$n$. This limitation is overcome and the velocity profile is obtained for all values of the Yasuda parameter by using the Lagrange inversion theorem, which admits power series solution for the flow field. An analytical solution for the concentration distribution in the circular tube is obtained for the unsteady and pulsatile flow with$n\leq 1$and$\alpha <<1$and the numerical solution is presented for all values of$\alpha$and$n$. The solute dispersion is analysed analytically using the Sankarasubramanian–Gill generalized dispersion method and also using the Aris–Barton method of moments considering up to fourth-order moments. The solute dispersion is also simulated numerically by using a new class of computationally explicit Runge–Kutta method. The axial mean concentration of the solute is estimated by the exchange, convective and dispersion coefficients. The third- and fourth-order moments give rise to skewness and kurtosis revealing the deviation from the Gaussianity and reduction in the peak of the mean concentration profile at a small time of the solute injection. All time variations of these five moments against flow governing parameters are thoroughly investigated. The flow and dispersion regimes that are derived here for moments provide a good understanding of the solute dispersion in the tube. The increase in the Womersley frequency parameter led to a phase lag at each period. This work is the initiation of estimating the skewness and kurtosis in a non-yield stress fluid flow in a tube.

Seafood consumption as a source of exposure to high production volume chemicals: A comparison between catalonia and the Canary Islands.

Seafood plays an important role in diet because of its health benefits. However, the fact that chemical compounds such as high production volume chemicals may be present in seafood means that its consumption can be a potential risk for population. To assess the occurrence of HPVs and estimate the exposure and risk associated with their consumption, specimens of the most consumed seafood species in Catalonia and the Canary Islands, Spain, were collected and analysed. Results showed higher levels of HPVs in samples from Catalonia and a prevalence of phthalate esters and benzenesulfonamides over the other target compounds in samples from both locations. Multivariate analysis showed spatial differences between the mean concentration profiles of HPVs for the samples from Catalonia and the Canary Islands. Exposures were higher for the samples from Catalonia, although the intake of HPVs via seafood was not of any real concern in either of the locations.

Using Mobile Monitoring and Atmospheric Dispersion Modeling for Capturing High Spatial Air Pollutant Variability in Cities

Air pollution is still one of the biggest environmental threats to human health on a global scale. In urban environments, exposure to air pollution is largely influenced by the activity patterns of the population as well as by the high spatial and temporal variability in air pollutant concentrations. Over the last years, several studies have attempted to better characterize the spatial variations in air pollutant concentrations within a city by deploying dense, fixed as well as mobile, low-cost sensor networks and more recently opportunistic sampling and by improving the spatial resolution of air quality models up to a few meters. The purpose of this work has been to investigate the use of properly designed mobile monitoring campaigns along the streets of an urban neighborhood to assess the capability of an operational air dispersion model as SIRANE at the district scale to capture the local variability of pollutant concentrations. To this end, an IoT ecosystem—MONICA (an Italian acronym for Cooperative Air Quality Monitoring), developed by ENEA, has been used for mobile measurements of CO and NO2 concentration in the urban area of the City of Portici (Naples, Southern Italy). By comparing the mean concentrations of CO and NO2 pollutants measured by MONICA devices and those simulated by SIRANE along the urban streets, the former appeared to exceed the simulated ones by a factor of 3 and 2 for CO and NO2, respectively. Furthermore, for each pollutant, this factor is higher within the street canyons than in open roads. However, the mobile and simulated mean concentration profiles largely adapt, although the simulated profiles appear smoother than the mobile ones. These results can be explained by the uncertainty in the estimation of vehicle emissions in SIRANE as well as the different temporal resolution of measurements of MONICA able to capture local high concentrations.

Dispersion of fine settling particles in a tidal wetland flow

An investigation on transport of fine sediment particles in a tidal wetland flow is presented in the current research. The model of this work is based on an advection diffusion equation whose solution reveals the water phase based concentration of settling particles. Using the method of moments, a system of moment equations are derived from the governing equation. A finite difference implicit scheme is employed to solve the equations of moment. The behavior of Taylor effective dispersivity due to the variation of settling velocity of fine particles for oscillatory current with or without nonzero mean is predicted. The mean concentration distribution along the longitudinal direction is obtained using the Hermite polynomial and first four central moments. It is shown that for greater settling velocity, the dispersion procedure is inhibited. Some significant effects of vegetation factor, time period, oscillation parameter on environmental dispersivity, skewness and mean concentration profile are shown. The results of the present study are very important to understand the process of sedimentation and wastewater treatment in a tidal wetland flow.

Corrosion protection mechanisms of graphene oxide-reinforced polypropylene coating for mild carbon steel by advanced molecular dynamics simulations with emphasis on resistance to water and chloride ion penetration

Polypropylene can be used as a raw material for manufacturing corrosion-resistant coatings to protect the surface of the mild carbon steel substrate. To improve the properties of polypropylene (PP), graphene oxide (GO) can be added to the coating. In this research, molecular dynamics (MD) simulations were employed to evaluate the effect of GO additives on the PP coating using COMPASS Force-Filed of the Forcite module. The results of molecular modeling, such as mean square displacement (MSD), diffusion coefficient, concentration profile, and gyration radius (Rg), revealed that the permeability of corrosive agents, including water molecules and chloride ions in the composite coating (PP/GO), is much lower than pure one (PP). In addition, by reducing the surface energy from 77 to 68 mJ/m2, the water contact angle (WCA) is improved from 150◦ for the pure PP coating to 170◦ for the composite one. It can also be due to an 18% increase in system compaction in the presence of GO. In the other hand, the free fraction volume (FFV) in the presence of GO is reduced by about 4%. The adhesion of the coating to the mild carbon steel substrate has also been ameliorated by 38% for the PP/GO coating compared to the pure PP. Therefore, most of the simulated parameters reported the positive effects of compositing PP with GO.

Net sheet-flow sediment transport rate: Additivity of wave propagation and nonlinear waveshape effects

Net wave-induced sheet-flow sediment transport rate, Qnet, can be produced by two co-existing effects: nonlinear waveshape and wave propagation, which alter the intra-wave boundary layer flow and sediment concentration. A intriguing question is whether the two effects can be simply added (the additivity hypothesis). This paper addresses this question based on simulations of a one-phase numerical model for sheet-flow sediment transport and examinations of the governing equations for boundary layer flow and sediment concentration. The additivity for the mean velocity (or streaming) is first demonstrated under typical field conditions. The main reason is that the two driving forces, i.e., momentum transfer produced by wave propagation and intra-wave asymmetry of flow turbulence produced by nonlinear waveshape, do not affect each other. The net sediment flux is separated into wave- and current-related components. Since the mean concentration profile is determined by the first-order process, the ‘current’-related flux produced by the two effects, following the mean velocity, can be superimposed. After examining the leading Fourier components, the wave-related flux is also found to follow the additivity hypothesis. The findings are confirmed by numerical experiments. The implication of this work is that a practical formula for Qnet can be designed with two separate components for nonlinear-waveshape and wave-propagation effects.

Effects of Atwood number and stratification parameter on compressible multi-mode Rayleigh–Taylor instability

This study numerically analyzes the two-dimensional (2D) compressible multi-mode Rayleigh–Taylor instability at different Atwood numbers (At) and stratification parameters (Sr), corresponding to the different levels of flow compressibility. It is found that the growth of bubble thickness is suppressed with the increase in Sr due to the density stratification at small At, whereas it is enhanced at large At, because of the expansion and compression motions. The ratio of the bubble to spike thickness increases with the increase in Sr at any At. The effects of the flow compressibility on the molecular mixing fraction, Taylor Reynolds number, turbulent Mach number, and velocity divergence statistics are similar at different Atwood numbers. The expansion and compression motions are enhanced by increasing the Sr and At. The expansion motions are relatively strong in the mixing layer, whereas the compression motions are prevalent outside the mixing layer, which may form a force promoting the upward movement of the bubble. The profiles of mean concentration, mean temperature, and root mean square of velocities can overlap with each other at different stratification parameters after normalization, which demonstrates the self-similarity of the 2D compressible Rayleigh–Taylor (RT) turbulence. The density stratification weakens the conversion from potential energy to kinetic energy, while the flow compressibility enhances the pressure-dilatation work at large values of Sr. The present results can help in the development of theoretical models of compressible RT turbulence.

Seasonality of nitrous acid near an industry zone in the Yangtze River Delta region of China: Formation mechanisms and contribution to the atmospheric oxidation capacity

HONO along with other trace gases and actinic flux were continuously measured in selected months from December 2015 to November 2016 near a major industrial zone of the Yangtze River Delta (YRD) region of China. The seasonalities of HONO and its formation mechanisms were explored. A box model was developed to assess the role of HONO chemistry in the atmospheric oxidative capacity in the study area. The model was constrained by in-situ observations to minimize simulation uncertainties. Our measurement results demonstrate that HONO mean concentration and diurnal profile varied noticeably between different seasons with the maximum (1.32 ± 0.92 ppbv) observed in winter, coincided with high mass loading of fine particles (PM2.5 = 114 ± 59.6 μg m−3). The averaged nighttime NO2 to HONO conversion ratios (hr−1) were (1.83 ± 0.73)% in spring, (2.91 ± 1.06)% in summer, (0.72 ± 0.44)% in autumn, and (0.84 ± 0.45)% in winter. The homogeneous reaction of OH + NO was responsible for a large portion of HONO production throughout the year but was relatively weaker compared to other mechanisms in winter. Heterogeneous reactions on ground surfaces were much stronger than those on aerosol surfaces, dominating nighttime HONO production, except in summer. Primary HONO emissions were only responsible for a small portion of the HONO budget. Particulate nitrate photolysis was a significant source of HONO and it showed very little variation in different seasons. OH budget analysis shows that O3 photolysis was a major contributor to the OH production in the study area while HONO photolysis provided an extra boost to the photochemical reactivity in the early morning, particularly during summer. However, HONO chemistry played a more important role in autumn and winter by dominating OH production throughout the day. Accordingly, effective control of NOx emissions dominated by industries can significantly reduce HONO production and thus weaken the atmospheric oxidative capacity in the study area.

Effect of food on exposure to napabucasin: Data from two phase I studies.

477 Background: Napabucasin is an orally-administered NAD(P)H quinone dehydrogenase 1–bioactivatable investigational agent hypothesized to affect multiple oncogenic cellular pathways including STAT3. Methods: Food effects on napabucasin pharmacokinetics were evaluated in two studies: one at two sites in Japan (Study 1; JapicCTI-205447) and the other at two sites in the US and three in Canada (Study 2; NCT01775423). Study 1 enrolled healthy Japanese male volunteers (HJMV) who received napabucasin 480 mg (formula 2) per sequential design — fasting on Day (D) 1 followed by a Japanese diet (JD) on D8 — with a 6-D intervening washout. In Study 2, patients (pts) with advanced malignancies received napabucasin 500 mg (formula 1) on D1 in the fasted state, then napabucasin 500 mg (formula 2) on D4 and D8 with a high-fat breakfast [HFB] or in the fasted state per the randomized sequence per crossover design. Results: In Study 1, mean plasma napabucasin levels 6–10 h after napabucasin 480 mg administration were higher in fed (JD) vs fasted states; in the fed state, Cmax increased by 15% and AUClast by ~60% (Table), while tmax decreased by ~1.4 hours. Adverse events (AEs) in Study 1 occurred in 5/6 (83.3%) HJMVs (fasted, n=3; fed, n=5; all grade [gr] 1). In Study 2, mean concentration profiles were comparable in fasted and fed (HFB) states for napabucasin 500 mg. When comparing fasted and fed states, Cmax increased by 21% and AUClast by 39% in the fed state (Table). Interpatient variability was high: geometric CV% for CL/F was 75.9% (fed) and 141% (fasted). AEs in Study 2 occurred in 68% (17/25) of fasted pts (gr 1: n=7; gr 2: n=8; gr 3, n=2) and 50% (7/14) of pts fed an HFB (gr 1: n=2; gr 2: n=3; gr 3, n=2). Conclusions: In HJMVs, napabucasin 480 mg administered with a JD increased exposure (Cmax; AUClast; AUCinf) and decreased tmax vs the fasted state. In pts with advanced malignancies, napabucasin 500 mg administered with an HFB increased exposure (Cmax; AUClast) vs the fasted state. These exposure increases are not considered to be of clinical relevance. Clinical trial information: JapicCTI-205447; NCT01775423. [Table: see text]

Scaling in concentration-driven convection boundary layers with transpiration

Abstract

Determination of the diffusivity, dispersion, skewness and kurtosis in heterogeneous porous flow. Part II: Lattice Boltzmann schemes with implicit interface

Abstract A simple local two-relaxation-time Lattice Boltzmann numerical formulation (TRT-EMM) of the extended method of moments (EMM) is proposed for analysis of the spatial and temporal Taylor dispersion in d-dimensional streamwise-periodic stationary mesoscopic velocity field resolved in a piecewise-continuous porous media. The method provides an effective diffusivity, dispersion, skewness and kurtosis of the mean concentration profile and residence time distribution. The TRT-EMM solves a chain of steady-state heterogeneous advection–diffusion equations with the pre-computed space-variable mass-source and automatically undergoes diffusion-flux jump on the abrupt-porosity streamwise-normal interface. The temporal and spatial systems of moments are computed within the same run; the symmetric dispersion tensor can be restored from independent computations performed for each periodic mean-velocity axis; the numerical algorithm recursively extends for any order moment. We derive an exact form of the bulk equation and implicit closure relations, construct symbolic TRT-EMM solutions and determine specific relation between the equilibrium and the collision degrees of freedom viewing an exact parameterization by the physical non-dimensional numbers in two alternate situations: “parallel” fracture/matrix flow and “perpendicular” Darcy flow through porous blocks in “series”. Two-dimensional simulations in linear Brinkman flow around solid and through porous obstacles validate the method in comparison with the two heterogeneous direct LBM-ADE schemes with different anti-numerical-diffusion treatment which are proposed and examined in parallel. On the coarse grid, accuracy of the three moments is essentially determined by the free-tunable collision rate in all schemes, and especially TRT-EMM. However, operated within a single periodic cell, the TRT-EMM is many orders of magnitude faster than the direct solvers, numerical-diffusion free, more robust and much more capable for accuracy improving, high Peclet range and free-parameter influence reduction with the mesh refinement. The method is an efficient predicting tool for the Taylor dispersion, asymmetry and peakedness; moreover, it allows for an optimal analysis between the mutual effect of the flow regime, Peclet number, porosity, permeability and obstruction geometry.

Determination of the diffusivity, dispersion, skewness and kurtosis in heterogeneous porous flow. Part I: Analytical solutions with the extended method of moments.

Abstract The extended method of moments (EMM) is elaborated in recursive algorithmic form for the prediction of the effective diffusivity, the Taylor dispersion dyadic and the associated longitudinal high-order coefficients in mean-concentration profiles and residence-time distributions. The method applies in any streamwise-periodic stationary d-dimensional velocity field resolved in the piecewise continuous heterogeneous porosity field. It is demonstrated that EMM reduces to the method of moments and the volume-averaging formulation in microscopic velocity field and homogeneous soil, respectively. The EMM simultaneously constructs two systems of moments, the spatial and the temporal, without resorting to solving of the high-order upscaled PDE. At the same time, the EMM is supported with the reconstruction of distribution from its moments, allowing to visualize the deviation from the classical ADE solution. The EMM can be handled by any linear advection-diffusion solver with explicit mass-source and diffusive-flux jump condition on the solid boundary and permeable interface. The prediction of the first four moments is decisive in the optimization of the dispersion, asymmetry, peakedness and heavy-tails of the solute distributions, through an adequate design of the composite materials, wetlands, chemical devices or oil recovery. The symbolic solutions for dispersion, skewness and kurtosis are constructed in basic configurations: diffusion process and Darcy flow through two porous blocks in “series”, straight and radial Poiseuille flow, porous flow governed by the Stokes–Brinkman–Darcy channel equation and a fracture surrounded by penetrable diffusive matrix or embedded in porous flow. We examine the moments dependency upon porosity contrast, aspect ratio, Peclet and Darcy numbers, but also for their response on the effective Brinkman viscosity applied in flow modeling. Two numerical Lattice Boltzmann algorithms, a direct solver of the microscopic ADE in heterogeneous structure and a novel scheme for EMM numerical formulation, are called for validation of the constructed analytical predictions.

Unsteady free convection oscillatory couette flow through a variable porous medium with concentration profile

In this paper we have studied the effect of free convection on the heat transfer and flow through variable porous medium which is bounded by two vertical parallel porous plates. In this study it is assume that free stream velocity oscillates with time about a constant mean. Periodic temperature is considered in the moving plate. Effect of different parameters on mean flow velocity, Transient velocity, Concentration profile and transient temperature studied in detail.

Influence of the secondary motions on pollutant mixing in a meandering open channel flow

This paper presents large eddy simulation of turbulent flow in a meandering open channel with smooth wall and rectangular cross-section. The Reynolds number based on the channel height is 40,000 and the aspect ratio of the cross-section is 4.48. The depth-averaged mean stream-wise velocity agree well to experimental measurements. In this specific case, two interacting cells are formed that swap from one bend to the other. Transport and mixing of a pollutant is analysed using three different positions of release, e.g. on the inner bank, on the outer bank and on the centre of the cross section. The obtained depth-average mean concentration profiles are reasonably consistent with available experimental data. The role of the secondary motions in the mixing processes is the main focus of the discussion. It is found that the mixing when the scalar is released on the centre of the cross-section is stronger and faster than the mixing of the scalar released on the sides. When the position of release is close to a bank side, the mixing is weaker and a clear concentration of scalar close to the corresponding side-wall can be observed in both cases.

Stochastic transport in the presence of spatial disorder: Fluctuation-induced corrections to homogenization.

Motivated by uncertainty quantification in natural transport systems, we investigate an individual-based transport process involving particles undergoing a random walk along a line of point sinks whose strengths are themselves independent random variables. We assume particles are removed from the system via first-order kinetics. We analyze the system using a hierarchy of approaches when the sinks are sparsely distributed, including a stochastic homogenization approximation that yields explicit predictions for the extrinsic disorder in the stationary state due to sink strength fluctuations. The extrinsic noise induces long-range spatial correlations in the particle concentration, unlike fluctuations due to the intrinsic noise alone. Additionally, the mean concentration profile, averaged over both intrinsic and extrinsic noise, is elevated compared with the corresponding profile from a uniform sink distribution, showing that the classical homogenization approximation can be a biased estimator of the true mean.

Mass transport analysis of non-Newtonian fluids under combined electroosmotically and pressure driven flow in rectangular microreactors

Hydrodynamically fully developed flow of power-law fluids under combined action of electroosmotic and pressure gradient forces in rectangular microreactors is analyzed considering heterogeneous catalytic reactions. The Poisson-Boltzmann, Cauchy momentum, and concentration equations are considered in two dimensions and after being dimensionless are numerically solved applying a finite difference algorithm. Variation of axial concentration gradient, and axial and horizontal mass diffusions are taken into account as well. To accomplish a more general analysis, the velocity distribution is obtained by solving continuity and Cauchy momentum equations and is not considered as an average axial velocity for solving the concentration equation. Profiles of mean concentration of reactants are analyzed as functions of operating variables. Results reveal that mean concentration increases with increasing Péclet number and dimensionless Debye-Hückel parameter. It is also a decreasing function of Damkohler number. Presence of pressure gradient will affect the decreasing trend of mean concentration through the channel. Shear-thinning fluids, due to their nature, are most strongly influenced by pressure gradient and Newtonian and shear-thickening fluids are less affected, respectively. Favorable pressure gradient will decelerate mean concentration rate of decrease and adverse pressure gradient acts the opposite. Moreover, a larger aspect ratio leads to slower descending rate of mean concentration in purely electroosmotic and pressure-assisted flows while in a pressure-opposed flow, the behavior might change depending on the strength of pressure gradient and the value of channel aspect ratio.

Computational study of mass and heat transport in a counterflowing turbulent round jet

This paper investigates the aspect of a hydraulic round jet issuing into a uniform counterflow under a range of jet-to-current velocity ratios. The prediction of the centerline dilution of jet effluent at velocity ratios ranging from 3 to 15 is performed using the Reynolds Stress Model (RSM). The penetration length is determined by considering the 5% contour of the centerline concentration and compared with empirical relationships suggested by previous researches. A similarity analysis is conducted on the radial profiles of both mean concentration and temperature at successive streamwise stations. The heat transport between the jet fluid and the opposed stream is also investigated with emphasis on the temperature effect on characteristics of the concentration field.