Mass Concentration Fields Research Articles

Integrated neural network based simulation of thermo solutal radiative double-diffusive convection of ternary hybrid nanofluid flow in an inclined annulus with thermophoretic particle deposition

Numerical simulation of magnetohydrodynamic radiative double-diffusive convective heat and mass transfer of a ternary hybrid nanofluid with thermophoretic particle deposition in an inclined annulus is studied. Both sides of cylinders are preserved at uniform temperatures, while the remaining sides are thermally insulated. The coupled nonlinear partial differential equations are solved using a finite difference approach. The detailed computational results of heat and mass transfer rate, temperature, concentration and flow fields are presented and discussed for a distinct range of significant physical parameters. The results demonstrated that increasing the angle of the inclination factor increases fluid flow. In light of buoyancy, when the annular cavity is set downward, the enhanced shear velocity is transported upwards, where it reaches its optimal temperature. The higher temperature difference leads to augmented dynamic fluid motion, particularly in the radial direction, as the system seeks to balance the thermal energy through convective transfer. The Brownian motion parameter has abrupt mobility of nanoparticles in liquid, which promotes particle collisions with liquid molecules, yielding kinetic energy. Increased values of thermophoretic parameters augment the thermophoresis force. Thermophoretic particle deposition increases the concentration of nanoparticles in an annulus due to the migration of particles from hot to cold regions under the influence of temperature gradient. The heat and mass transfer characteristics of ternary hybrid nanofluid are forecasted through an artificial neural network-based Levenberg–Marquardt backpropagated algorithm. The built model shows the heat and mass transfer rate root mean squared values through the Levenberg–Marquardt algorithm as one and mean squared error values as 1e-07 and 1e-08 respectively.

Axisymmetric problem in modified couple stress thermoelastic with void, diffusion and phase lags

The present work is focused on investigating the axisymmetric deformation in a thick circular plate with a heat source in modified couple stress thermoelastic (MCT) under void, diffusion, and phase lags impacts. The new set of governing equations is formulated and solved by using Laplace and Hankel transform techniques after converting the system of equations into dimensionless form and using the potential functions. The plate is subjected to a ramp-type heat source along with a thermal source, mass concentration source, and source over volume fraction field of voids (SVFV). For application, particular types of sources are taken to demonstrate the utility of the problem. The physical quantities like displacements, temperature field, mass concentration, chemical potential, and volume fraction field are determined analytically in the closed form. A numerical mathematical technique is employed to determine the resulting quantities for the original region and displayed in form of graphs to examine the different physical effects. The problem is validated by comparing results with those obtained by different authors. The results provide a motivation to investigate thermal conducting modified couple stress elastic solid under the physical impact of mass diffusion, porosity and phase lags as a new class of material. The present work is very much expected to be useful for various deformation and vibration problems in geophysics, material science, engineering, and biothermoelastic materials.

Improving the GaN Growth Rate by Optimizing the Nutrient Basket Geometry in an Ammonothermal System Based on Numerical Simulation.

The low growth rate of bulk gallium nitride (GaN) when using the ammonothermal method is improved herein by optimizing the nutrient geometry. A numerical model considering the dissolution and crystallization process is developed. Heater powers are employed as thermal boundary conditions to match the real ammonothermal system. The flow field, thermal field, and mass concentration field in the autoclave are calculated with or without a central hole in the nutrient basket. Numerical results show that the mass transfer efficiency and supersaturation on the seed crystal surface can be improved with a hole in the nutrient basket in the center in spite of its diverse effect on the heat transfer, which can be overcome by adjusting the heater powers. As a result, the growth rate of the GaN crystal can be obviously increased.

Simulations of micropolar nanofluid-equipped natural convective-driven flow in a cavity

PurposeThis paper aims to focus on the natural convective flow analysis of micropolar nanofluid fluid in a rectangular vertical container. A heated source is placed in the lower wall to generate the internal flow. In further assumptions, the left/right wall are kept cool, while the upper and lower remaining portions are insulated. Free convection prevails in the regime because of thermal difference in-between the lower warmer and upper colder region.Design/methodology/approachThe physical setup owns mathematical framework in-terms of non-linear partial differential equations. For the solution purpose of the differential system, finite volume method is adopted. The interesting features of the flow along with thermal transportation involve both translational and rotational movement of fluid particles.FindingsPerforming the simulations towards flow controlling variables the outputs are put together in contour maps and line graphs. It is indicated that the variations in flow profile mass concentration and temperature field augments at higher Rayleigh parameter because of stronger buoyancy effects. Higher viscosity coefficient implies decrease in flow and thermal transportation. Further, the average heat transfer rate also grows by increasing both the Rayleigh parameter and heated source length.Originality/valueTo the best of the authors’ knowledge, no such study has been addressed yet. Further, the results are validated by comparing with previously published work.

Thermo-Solutal Convection of a Nanofluid Utilizing Fourier’s-Type Compass Conditions

Nanotechnology has infiltrated into duct design in parallel with many other fields of mechanical, medical and energy engineering. Motivated by the excellent potential of nanofluids, a subset of materials engineered at the nanoscale, in the present work, a new mathematical model is developed for natural convection in a vertical duct containing nanofluid. Numerical scrutiny for the double-diffusive free and forced convection within a duct encumbered with nanofluid is performed. Buongiorno’s model is deployed to define the nanofluid. Robin boundary conditions are used to define the surface boundary conditions. Thermal and concentration equations envisage the viscous, Brownian motion, thermosphores of the nanofluid, Soret and Dufour effects. Using the Boussi-nesq approximation the solutal buoyancy effect as a result of gradients in concentration are incorporated. The conservation equations which are nonlinear are numerically estimated using fourth order Runge-Kutta methodology and analytically ratifying regular perturbation scheme. The mass, heat, nanoparticle concentration and species concentration fields on eight dimensionless physical parameters such as thermal and mass Grashof numbers, Brownian motion parameter, thermal parameter, Prandtl number, Eckert number, Schmidt parameter, and Soret parameter are calculated. The impact of these parameters are outlined pictorially. The velocity and temperature fields are boosted with the thermal Grashof number. The Soret and the Schemidt parameters reduces the nanoparticle volume fraction but it heightens the momentum, temperature and concentration. At the cold wall thermal and concentration Grashof numbers reduces the Nusselt values but they increase the Nusselt values at the hot wall. The reversal consequence was attained at the hot plate. The perturbation and Runge-Kutta solutions are equal in the nonappearance of Prandtl number. The (E. Zanchini, Int. J. Heat Mass Transfer 41, 3949 (1998)). results are restored for the regular fluid. The heat transfer rate is high for nanofluid when matched with regular fluid.

Modeling of the dispersion of pollutants in porous media: Case of a landfill in Brazil

Municipal solid waste (MSW) disposal systems are still a sanitary and environmental problem. The high concentration of toxic substances existing in liquids arising from the decomposition of waste, present a risk to human health and the environment. It is necessary to establish mechanisms to predict leachate dispersion in order to determine possible scenarios and control systems. This work investigates the dispersion of leachate from urban solid waste through saturated soil. The municipal landfill of Jacarezinho in Brazil is the focus of the study. The conceptual model was based on existing data from geology, hydrology, hydrogeology and leachate characterization. The codes MODFLOW and MT3DMS were used and the dispersion of chromium, copper, lead and zinc was simulated. Pollutant mass concentration fields were calculated in 1, 5, 10, 25 and 50 years. The results indicated that the pollutants could reach the Ouro Grande River, in a period of 5 years and the tributary in a period of 1 year of the initial generation of leachate. For the final period of the simulation, the tributary of the Ouro Grande River received copper and lead concentrations that exceeded the maximum values ​​allowed in Brazilian legislation for the watercourse quality standard. It was concluded that the Jacarezinho landfill has the potential to pollute the surrounding soil and groundwater.

Influence of Soret and Dufour on forced convection flow towards a moving thin needle considering Buongiorno’s nanofluid model

This article concerns the study of forced convection flow, heat and mass transfer near a moving slender needle using the Buongiorno nanofluid model. Soret and Dufour impacts are analyzed to study the thermo-diffusion and diffusion-thermo impacts on the flow. The governing boundary layer equations are turned into a dimensionless one with the assistance of similarity transformations. After that those ordinary differential equations are computed by a bvp4c package in MATLAB program. Subsequently, the influences of relevant variables on the coefficient of skin friction, heat and mass transfer rate, momentum, temperature and concentration fields are depicted through the graphical approach and have been interpreted in detail. Extracted outcomes are also authenticated with the existing articles. The multiple solutions are noticed to show up in particular ranges of several parameters. The stability of solutions is conducted to find which of the solution gained is linearly stable. The results indicate that the solution for the upper branch is stable, while the solution for the lower branch is unstable. The outcomes also revealed that the percentage of heat and mass transmission rate diminishes by 40.43% and 31.41%, respectively, with the increment in the needle thickness from b=0.1 to b=0.2.

Dispersion Characteristics of PM10 Particles Identified by Numerical Simulation in the Vicinity of Roads Passing through Various Types of Urban Areas

The dispersion of particulate matter emitted by road transport to the vicinity of roads is predominantly influenced by the character of the air velocity field. The air flow depends on factors such as the speed and direction of the blowing wind, the movement of cars, and the geometries of the buildings around a road. Numerical modeling based on the control volume method was used in this study to describe the relevant processes closely. Detailed air velocity fields were identified in the vicinity of a straight road surrounded by various patterns of built-up urban land. The evaluation of the results was generalized to exponential expressions, affecting the decrease of the mass concentration of fine particles with the increasing distance from the road. The obtained characteristics of the mass concentration fields express the impact of the building geometries and configurations on the dispersion of particulate matter into the environment. These characteristics are presented for two wind speeds, namely, 2 m·s−1 and 4 m·s−1. Furthermore, the characteristics are introduced in relation to three wind directions: perpendicularly, obliquely, and in parallel to the road. The results of the numerical simulations are compared with those obtained via the in-situ measurements, for verification of the validity of the linear emission source calculation.

Entropy generation minimization in a channel flow: Application to different advection-diffusion processes and boundary conditions

Heat and mass transfer enhancement in a convective flow is studied using a variational optimization technique. Entropy generation rate is minimized while allowing to vary the relative weight of the total viscous dissipation in the objective functional to determine optimized velocity and scalar field patterns. The resulting velocity, thermal and mass concentration fields are analyzed as well as the influence of boundary conditions. The relative improvement of the optimized solutions is assessed and heat transfer vs. mass diffusion results are compared. The optimization approach leads to improved entropy generation rates. The viscous dissipation weighting factor influences the entropy generation rates and the velocity and scalar field patterns. A transition between two levels of perturbation by comparison to non-optimized flows occurs at a critical value of the weighting factor that depends on the boundary conditions. The flow patterns obtained by variational optimization can be the basis for enhanced exchanger design.

Mass transfer characteristics and concentration field evolution for gas-liquid Taylor flow in milli channels

The results of the recent experimental work performed by Butler et al. (2016, 2018) are analysed based on the dominant phenomena: (i) small scale convection by means of Taylor vortices in the liquid slugs and (ii) diffusion in lubrication film. A main result shown here is that the Taylor circulation frequency is able to reflect the global mass transfer rate in gas-liquid Taylor flow through an almost linear relationship, which emphasizes the interest of the circulating motion in the slug, and gives a very simple correlation to predict the kLa value (at large Schmidt number). A mechanism of flow behavior during the bubble formation at the T-mixer is proposed as a possible explanation of unexpected concentration areas (called “islands”). However, despite of these unusual concentration field structures in these cases, the mass transfer rate coefficient kLa is still accurately predicted by the Taylor circulation frequency in the slug.

Thermodynamics of magnetohydrodynamic Brinkman fluid in porous medium

This research article investigates that how heat flow changes versus temperature or time on the rheology of magnetohydrodynamic Brinkman fluid embedded in porous medium for the oscillations of heated plate. A fractional approach namely Caputo–Fabrizio fractional operator is applied for developing the governing partial differential equations of Brinkman fluid flow. The fractional governing partial differential equations have been modeled for temperature distribution, mass concentration and velocity field along with imposed initial and boundary conditions. The solutions are obtained by integral transforms and presented in special and elementary functions. In the limiting sense, the analytical solutions are particularized in the presence and absence of heat and mass transfer, magnetic field and porous medium. The parametric graphs have been depicted for the influence of different embedded rheological parameters on fluid flow. The results show few interesting differences and similarities by comparative analysis for fractional and ordinary Brinkman fluid flow, such as physically higher Prandtl (Pr) number that leads to decay thermal diffusivity which results in the reduction in thermal field; this means that better quality of production can be achieved through proper choice of Prandtl (Pr) and Schmidt (Sc) numbers.

Analytical Solutions of Fractional Walter’s B Fluid with Applications

Fractional Walter’s Liquid Model-B has been used in this work to study the combined analysis of heat and mass transfer together with magnetohydrodynamic (MHD) flow over a vertically oscillating plate embedded in a porous medium. A newly defined approach of Caputo-Fabrizio fractional derivative (CFFD) has been used in the mathematical formulation of the problem. By employing the dimensional analysis, the dimensional governing partial differential equations have been transformed into dimensionless form. The problem is solved analytically and solutions of mass concentration, temperature distribution, and velocity field are obtained in the presence and absence of porous and magnetic field impacts. The general solutions are expressed in the format of generalized Mittag-Leffler function MΩ2,Ω3Ω1χ and Fox-H function Hp,q+11,p satisfying imposed conditions on the problem. These solutions have combined effects of heat and mass transfer; this is due to free convections differences between mass concentration and temperature distribution. Graphical illustration is depicted in order to bring out the effects of various physical parameters on flow. From investigated general solutions, the well-known previously published results in the literature have been recovered. Graphs are plotted and discussed for rheological parameters.

Simulation of size-dependent aerosol deposition in a realistic model of the upper human airways

An Eulerian internally mixed aerosol model is used for predictions of deposition inside a realistic cast of the human upper airways. The model, formulated in the multi-species and compressible framework, is solved using the sectional discretization of the droplet size distribution function to accurately capture size-dependent aerosol dynamics such as droplet drift, gravitational settling and diffusion. These three mechanisms are implemented in a consistent way in the model, guaranteeing that the total droplet mass as given by the droplet size distribution is always equal to the total droplet mass due to the mass concentration fields. To validate the model, we simulate monodisperse glycerol aerosol deposition inside the lung cast, for which experimental data is available. Provided that an adequate computational mesh is used and an adequate boundary treatment for the inertial deposition velocity, excellent agreement is found with the experimental data. Finally, we study the size-dependent deposition inside the lung cast for a polydisperse aerosol with droplet sizes ranging from the nanometer scale to beyond the micrometer scale. The typical ‘V-shape’ deposition curve is recovered. The aim of this paper is to 1) provide an overview of the Eulerian aerosol dynamics model and method, to 2) validate this method in a relevant complex lung geometry and to 3) explore the capabilities of the method by simulating polydisperse aerosol deposition.

Dual solutions of an unsteady flow, heat and mass transfer of an electrically conducting fluid over a shrinking sheet in the presence of radiation and viscous dissipation

In this study we analyze the effects of thermal radiation and surface mass transfer on the flow generated by a shrinking sheet. Homotopy analysis method (HAM) is employed to obtain analytical solutions for the flow, temperature and mass concentration fields. The plots for the velocity, temperature and concentration fields are presented and their behavior is discussed for several sets of values of the governing parameters. Dual solutions are observed to exist for the shrinking sheet problem. Surface drag coefficient of the stable solution is enhanced for increasing values of the magnetic parameter and suction parameter. Also, thermal radiation parameter and Eckert number increase the rate of heat transfer in the case of stable solution. However, mass transfer rate of the stable solution is noticed to be a decreasing function of Schmidt number and chemical reaction parameter. We expect that the results obtained will not only provide useful information for industrial applications but also complement the existing literature.

Analysis of the heat and mass transfer in the MHD flow of a generalized Casson fluid in a porous space via non-integer order derivatives without a singular kernel

This article investigates the effects of the non-integer order derivative without singular kernel on the double convection MHD flow of a Casson fluid with and without a magnetic field and a porous medium over an oscillating vertical plate. The governing equations of the mass concentration, temperature distribution and velocity field have been converted using the Fabrizio–Caputo fractional derivative. The analytical solutions have been traced out for the mass concentration, temperature distribution and velocity field. The general solutions for the mass concentration, temperature distribution and velocity field have been expressed in terms of the newly defined Mittage–Leffler and Fox-H functions, respectively. Some similarities and differences have focused on the concentration, temperature and velocity by specifying a few emerging parameters for the fluid flow. Finally, a graphical illustration has been presented by employing the pertinent parameters of the fluid flow, and it is noted that the ordinary and Caputo–Fabrizio fractional fluid models have a reciprocal behavior for the fluid flow.

Non-linear Differential Equations and Rotating Disc Electrodes: Padé approximationTechnique

Rotating disc electrodes are preferred devices to analyze electrochemical reactions in electrochemical cellsand various rotating machinery such as fans, turbines, and centrifugal pumps. This model contains system of fully coupled and highly non-linear equations. This manuscript outlines the steady state solution of rotating disc flow coupled through the fluid viscosity, to the mass-concentration field of chemical species and heat transfer of power-law fluid over rotating disk. Furthermore, a simple analytical expression (Padé approximation) of velocity component/ self-similar velocity profiles is derived from the short and long distance expression. Our analytical results for all distance are compared with previous small and long distance and numerical solutions (Runge-Kutta method), which are in satisfactory agreement.

Particle Size Distribution and Diffusion for Simulated Cooking Fume

Studying particle size distribution and dispersion characteristics of cooking oil fume can help to analyze the influence of the particles on indoor air quality and the health of the residents.Electrical low pressure impactor (ELPI) was employed to measure the number and mass concentration of the particles size range of 0.03-10 μm at two different locations in the kitchen space with smoke exhaust on and off,respectively.The cooking particles were mostly located at below 655 nm.The smoke exhaust with open condition could remarkably decrease the kitchen's cooking fume.The number concentration of particles decreased from 2.8×106 cm-3 to 2.3×105 cm-3,and PM2.5(aerodynamics diameter ≤2.5 μm particulate matter) mass concentrations decreased from 85.9 mg·m-3 to 6.2 mg·m-3.The sucking efficiency of smoke exhaust for PM10 was higher than PM2.5.The number concentration of particles could be declined by 65%,and the cooking fume of PM2.5 could be declined by 75% during the diffusion process detected at the area of 3 m far away from the area where cooking took place.The distribution of PM2.5 mass concentration field of oil fume was simulated by computational fluid dynamics.The temperature field distribution of oil fume was monitored by infrared camera,presenting sector diffusion with the temperature decreasing from 70℃ to room temperature.

Generalized coupled non-Fickian/non-Fourierian diffusion-thermoelasticity analysis subjected to shock loading using analytical method

In this article, the generalized coupled non-Fickian diffusion-thermoelasticity analysis is carried out using an analytical method. The transient behaviors of field variables, including mass concentration, temperature and displacement are studied in a strip, which is subjected to shock loading. The governing equations are derived using generalized coupled non-Fickian diffusion-thermoelasticity theory, which is based on Lord-Shulman theory of coupled thermoelasticity. The governing equations are transferred to the frequency domain using Laplace transform technique and then the field variables are obtained in analytical forms using the presented method. The field variables are eventually determined in time domain by employing the Talbot technique. The dynamic behaviors of mass concentration, temperature and displacement are studied in details. It is concluded that the presented analytical method has a high capability for simulating the wave propagation with finite speed in mass concentration field as well as for tracking thermoelastic waves. Furthermore, the obtained results are more realistic than that of others.

Boundary integral formulation for interfacial cracks in thermodiffusive bimaterials

An original boundary integral formulation is proposed for the problem of a semi-infinite crack at the interface between two dissimilar elastic materials in the presence of heat flows and mass diffusion. Symmetric and skew-symmetric weight function matrices are used together with a generalized Betti's reciprocity theorem in order to derive a system of integral equations that relate the applied loading, the temperature and mass concentration fields, the heat and mass fluxes on the fracture surfaces and the resulting crack opening. The obtained integral identities can have many relevant applications, such as for the modelling of crack and damage processes at the interface between different components in electrochemical energy devices characterized by multi-layered structures (solid oxide fuel cells and lithium ions batteries).

Numerical Simulations of Wind Induced Particle Contamination in Gypsum Landfill Surroundings

The contribution presents numerical simulation of gypsum particles, lifting from a gypsum landfill. First, particle characteristics are presented, resulting from different technologies of gypsum depositing. Next, a laboratory experiment parameter validation tests are described, which served as a means of determination of mass flow of particles from the landfill. The background of the numerical simulations, used in the assessment of landfill impact on the environment, is also described. Simulations consist of two parts: simulation of a long term impact of the particles on the surrounding area, performed by implementation of the Gaussian dispersion model based computer code ISC3, and second, a CFD based simulation for assessing the flow and mass concentration fields in the vicinity of the landfill for several pre-selected flow cases. The results of both computational approaches are presented and compared. In the conclusions, a relation of the simulation results with existing environmental pollution levels is made, and recommendations for landfill management are drawn.