Abstract
The objective of this work is to investigate the influences of thermal radiation, heat generation, and buoyancy force on the time-dependent boundary layer (BL) flow across a vertical permeable plate. The fluid is unsteady, incompressible, viscous, and electrically insulating. The heat transfer mechanism happens due to free convection. The nondimensional partial differential equations of continuity, momentum, energy, and concentration are discussed using appropriate transformations. The impressions of thermal radiation and buoyancy forces are exposed in the energy and momentum equation, respectively. For numerical model, a set of nonlinear dimensionless partial differential equations can be solved using an explicit finite difference approach. The stability and convergence analyses are also established to complete the formulation of the model. The thermophysical effects of entering physical parameters on the flow, thermal, and material fields are analyzed. The variations in local and average skin friction, material, and heat transfer rates are also discussed for the physical interest. The analysis of the obtained findings is shown graphically, and relevant parameters pointedly prejudice the flow field. Studio Developer FORTRAN 6.2 and Tecplot 10.0 are applied to simulate the schematic model equations and graphical presentation numerically. The intensifying values of the magnetic field are affected decreasingly in the flow field. The temperature profiles decrease within the BL to increase the value of radiation parameters. The present study is on the consequences for petroleum engineering, agriculture engineering, extraction, purification processes, nuclear power plants, gas turbines, etc. To see the rationality of the present research, we compare these results and the results available in the literature with outstanding compatibility.
1. Introduction
MHD is the magnetic field that may produce currents in a fluid that magnetizes the fluid and alters the magnetic field. It is utilized in a variety of areas, including astrophysics, geophysics, sensors, earthquakes, engineering (such as plasma confinement, cooling of nuclear reactors, liquid-metal and polymer technology, and electromagnetic casting), biomedical engineering (like magnetic drug targeting, magnetic devices for cell separation, magnetic endoscopy, cancer tumor treatment, and cell death by hyperthermia), and meteorology, which is created by an alternating magnetic field. Many fields of research and engineering employ porous media, including filtration mechanics, soil mechanics, rock mechanics, groundwater hydrology and petroleum engineering, material science, geoscience, biology and biophysics, and metal forming. Heat convection in a porous medium serves the purposes of energy recovery, thermal energy storage, geothermal oil extraction, natural environment ventilation, central heating, and the flow of filtration devices. The simultaneous occurrence of heat and mass transfer in a moving fluid is crucial to designing chemical processing equipment, nuclear power plants, gas turbines, and thermal energy storage. The free convection flow often occurs in nature; fluid flows through porous media with magnetic fields are of particular interest and have attracted many scientists and engineers owing to their applications in science and industry.
Ahmed and Alam [1] investigated the finite-difference solution of magnetohydrodynamics (MHD) mixed convection flow with chemical reaction and heat production. Ahmed et al. [2] studied naturally convective flow in water-copper nanofluid-filled circular and arc cavities. Olajuwon and Oahimire [3] investigated the effects of thermal radiation and Hall current on heat and mass transfer of unsteady MHD flow in saturated porous media containing a viscoelastic micropolar fluid. Das and Jana [4] studied natural convective magneto-nanofluid flow and thermal transmission across a vertically moving plate. Samiulhaq [5] investigated the influence of MHD free convection flow and a porous medium on thermal diffusion and ramping wall temperature. Reddy [6] observed unsteady MHD convection heat and mass transfer flow over a vertical semi-infinite porous plate with changing viscosity and thermal conductivity. Makinde and Aziz [7] examined the effects of MHD mixed convection flow across a vertical plate contained in a porous media and subjected to a transverse magnetic field. Reddy et al. [8] investigated the numerical solution of transient natural convection MHD radiation flow through a vertical cylinder contained in a porous medium with varying surface temperatures and concentrations.
Ali et al. [9] conducted a numerical simulation of heat and mass transfer over a stretched wedge surface and identified the nanoparticle concentration solution for Brownian motion less than 0.2, thermophoresis less than 0.14, and Lewis number more than 1. Tarammim et al. [10] observed MHD free convection flow over a vertical plate. Alam et al. [11] obtained the numerical solution of coupled free-forced convection and mass flow through a vertical permeable medium with heat production and thermal transmission. Shamshuddin et al. [12] explored the effects of the thermal Péclet number, vortex viscosity, and Reynolds number on the two-dimensional flow of micropolar fluid through a channel owing to mixed convection. Ullah et al. [13] demonstrated magneto-convective flow over a vertical plate with radiation. Islam et al. [14] triumphed over the mathematical forming of a flow field with uniform/nonuniform thermal and magnetic strength in a half-moon-shaped region. The authors found that after the nondimension time of about 0.65, the numerical solution reached a steady-state phase from unsteadiness, and the rate of thermal transmission rises for rising buoyancy force whereas devalued with the elevated magnetic field. Magneto-convective flow over an inclined plate with Hall current was conquered by Alam et al. [15].
Abdullameed et al. [16] revealed closed from solutions for unsteady MHD flow in a permeable medium with wall transpiration. Shamshuddin and Ghaffari [17] investigated radiative heat energy on Casson-type nanoliquid generated by a convectively heated porous medium in combination with thermophoresis and Brownian motion effects. Chamkha et al. [18] observed turbulent spontaneous convective power-law fluid flow across a vertical plate embedded in a non-Darcian porous medium with a homogenous chemical reaction.
The innovation of this investigation is to explore the numerical solutions of magneto-convective heat and mass fluid flow over a vertical permeable plate with thermophysical parameters. The main novelty of this research is considering the influence of nine parameters and dimensionless numbers combinedly with the permeable plate. Also, it is required to study the inclusion of expressions on flow, thermal, and material profiles, as well as local and average Sherwood numbers, Nusselt number, and shear stress fluctuations in thermophysical and hydrodynamical parameters. In the first stage, the governing equations are established and mathematical analysis is given. The results and discussions including the graphs, tables, and comparisons are presented in the second stage. Finally, the significant outcomes of this investigation are summarized. Thereafter, future works and significant references related to this research work are included.
2. Formulation of Problem
The presentation of the two-dimensional unsteady fluid model with magneto-convective heat and mass transfer is analyzed in this research by adding thermal radiation and heat generation. According to Ali et al. [19], our research schedule is displayed in Figure 1.
2.1. Physical Model
Consider the trembling two-dimensional nonlinear MHD free convection flows of a viscoelastic, deformable, and electrically insulating fluid around a vertical plate embedded in porous media. This is happening while the thermal and material buoyancy effects are being encouraged. Figure 2 depicts the entire flow mechanism structure with the appropriate coordinates. The -axis is placed along the porous plate in a vertically upward orientation. Consequently, is a function of and only, i.e., . Let and represent the velocity components in the and directions, respectively. Initially, both the plate and fluid are the same at the temperature. Instantaneously, the plate temperature and species concentration are raised to and , respectively.
Typically, a consistent magnetic field is applied to the plate. All assumptions and approximations for the model flow are given as follows: (i)The induced magnetic field is insignificant compared to the applied magnetic field(ii)The Joule heating effects are negligible in the energy equation(iii)The magnetic Reynolds numbers and effective transversal magnetic field are insignificant(iv)No applied electric force is expected(v)The electric field is assumed to be zero(vi)Viscous dissipation is used to quantify the temperature gradient of fluid particles within the surface of a flat plate(vii)Flow in the medium is caused by the buoyancy force generated by the temperature gradient between the fluid and the porous plate(viii)Under the Rosseland [20] approximation of radiative heat flow with Taylor series expansion, the thermal radiation is employed in a way that may be well estimated
Under the above hypotheses and Boussinesq’s approximation and following Nasrin and Alim [21, 22], the equations of continuity, momentum, energy, and concentration can be put mathematically in the following form.
The corresponding boundary conditions, according to Ali et al. [23–25], are
Here, is the constant magnetic field, is the kinematic viscosity, is the coefficient of volumetric expansion, is the coefficient of expansion with concentration, is the electric conductivity, is the heat release per unit mass, is the thermal conductivity, is the radiated heat flux, is the coefficient of mass diffusivity, and is the uniform velocity of the fluid, whereas the other symbols retain their ordinary meanings.
2.2. Mathematical Formulation
The subsequent usual transformations are introduced to make the nondimensional system of partial differential equations (PDEs) with boundary conditions (BCs).
Replacing the above transformation into equations (1), (2), (3), and (4) and consistent BCs (5) and applying some mathematical manipulation, the following nonlinear PDEs in expressions of dimensionless variables are
The BCs are where Grashof number , solutal Grashof number , magnetic parameter , porosity parameter , Prandtl number , Eckert number , radiative parameter , Schmidt number , and heat generation parameter .
2.3. Declaration of Physical Exigent Quantities in Engineering Inquisitiveness
The local skin friction coefficient and Sherwood number are the main physical curiosities in the engineering field. Typically, the shear stress at the plate is denoted by the skin friction coefficient. In compliance with Hossain et al. [26, 27] and Das et al. [28, 29], the nondimensional form of the local shear stress at the plate in the direction is defined by and average shear stress in the direction . Sherwood number is well known for the local mass transfer rate.
The local Sherwood number is signified by , while the average Sherwood number is . The Nusselt number is a well-known measure of the local heat transmission rate. The local Nusselt number is provided by the denoted , and the average Nusselt number is inscribed as .
3. Computational Technique
The nondimensional governing set of nonlinear PDEs can be explained numerically with relevant BCs with an explicit finite difference method (FDM). The flow zone is divided into a grid of lines corresponding to the - and -axes, with the -axis measured along the plate and the -axis parallel to the fluid flow, to get the difference equations. Due to this bifurcation, these time- and space-dependent finite difference equations are discretized. In this study the plate of the size (=100) is measured, that is, fluctuates between 0 and 100 and supposed (=25) as corresponding to , that is, it ranges between 0 and 25. Estimation is used to conduct the computation for numerical methods based on random trials of meshes with varying values. Figure 3 shows a visualization of the development of this mesh space. There are and grid layout in the and conducted separately and occupied as trails and with respect to the minimal time phase, . The phrase determines the value of throughout each iteration of the loop. The extreme value of is determined when the successful loop results in no change in the value of the unknown BCs at . Here, , , and signify the value of , , and at the culmination of a time phase individually.
Exhausting the explicit FDM into the PDEs ((8) and (9)), we get with boundary conditions
, where .
Here, and stand for the nodes with coordinates, is the temperature, and is concentration.
3.1. Stability and Convergence Analyses
Stability analysis is an essential tool that gives a good prediction of the convenience of a problem. It is helpful to analyze stability before we go to accurate computations. So, it represents that our numerical solutions can be trusted and is reliable. Ingredients for the entire stability computing process are the minor time phase and the mesh phase values. According to Ali et al. [30], the general expressions of the Fourier expansion for an arbitrary time, say, , are and , where .
Then,
And after the time step, we get
Substituting equations (17) and (18) into equations (10)–(16), the following equations are obtained upon simplification. where where where
Equations (19), (23), and (25) can be written as where and .
Equations (28), (31), and (32) can be written as where
To obtain the stability condition, it is necessary to realize the eigenvalues of the augmentation matrix .
For this reason, let .
So, matrix can be expressed as
Thus, the eigenvalues are .
For stability, each eigenvalue must not exceed in modulus.
Hence, the stability condition is
Let, .
Hence, ,
The coefficients of are real and nonnegative. So, the maximum modulus of occurs when and where and are integers, and hence, are real. When and are odd integers, the amounts of are maximum. So we get
To satisfy the greatest negative allowable values are
So, the converging restrictions for the FDM solution schemes are
Likewise, the second condition
The third condition
The values , , and , along with the initial circumstances that determine the convergence requirements of the method, are and with stable constraints materially.
3.2. Questing for Suitable Mesh
After repeated experiments with various mesh sizes, the ideal mesh size is strategically significant for the flow model inside the boundary layer flow. The acquaintance with the graphs’ smoothness and convergence leads us to conclude that the mesh size can be measured for numerical designs.
3.3. Questing Steady State
The uninterrupted testing of various parameter values attains the steady-state scenario for the flow model equations. The steady-state controls for magnetic field on shear stress , , , and are presented in Figure 4, with , , , , , , , , and . Observations show that the consequence of the magnetic field on shear stress expresses minor fluctuation at and while and exhibit almost ineffectual variations as an acquisitive steady state for the revealing fields. The steady-state performance is exposed in (Table 1).
3.4. Verifications of the Consequence of Parameter
The magnitudes of the Grashof number on concentration profile are given different values for radiation and in the absence of radiation which assures the accuracy of the effect of the parameter. This experimentation is demonstrated through Figures 5(a) and 5(b), with , , , , , , , , and , , , , , , , , . In the presence of radiation/absence of radiation, curve-to-curve fluctuation on concentration profiles is shown in (Table 2).
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3.5. Verifications of Codes with the Reported Results
The published result of Deepthi et al. [31] and the present results show excellent potential. The results of the pictorial matching are shown in Figures 6(a) and 6(b). The effects of heat generation on the temperature inside the boundary layer are carried out in this comparison.
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4. Results with Explications
To attain the physical implication of the problems, we have plotted flow, thermal, material, Sherwood number, Nusselt number, and skin friction for distinct values of physical fields like magnetic parameter (), Prandtl number (), Eckert number (), porosity (), and Schmidt number (). The following default parameter values are assumed for computations in the present study: , , , , and . To be realistic, the numerical values of the Prandtl number are chosen as 1, 1.38, and 7.2, which correspond to salt water, ammonia, and seawater (at 20°C), respectively. Also, the typical values of Schmidt number are preferred for hydrogen (0.22), ethyl ether (1.66), and toluene (1.84) at 25°C and 1 atm, which denotes the diffusion of the most prevalent chemical species. The numerical values for the remaining parameters are determined at random. Grashof number (), solutal Grashof number (), radiation (), and heat generation () are kept constant.
4.1. Influence of Magnetic Field
Figures 7(a)–7(c) show flow, thermal, and concentration profile trends for various values of the magnetic parameters while maintaining the remaining parameters constant. Figure 7(a) demonstrates that the velocity decreased for increasing values of (Table 3). It is a known fact that a transverse magnetic field in proximity to an electrically conducting fluid will cause an increase in the body force known as the Lorentz force. This force tends to resist the flow of the fluid and slow down its motion in the BL region. In consequence, tangential velocity falls. In Figure 7(b), it is apparent that the temperature of the fluid rises in and then falls as the value of increases (Table 4). Figure 7(c) depicts that the concentration profiles decrease for enhancement of (Table 5), indicating that it slows the rate of heat convection in the flow; hence, the flow temperature seems to rise, and the concentration gradient decreases. Figures 7(d) and 7(g) show that local and average Nusselt number declines for growing values of . Figures 7(e) and 7(h) show that the local and average Sherwood number upsurges for rising values of .
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Figures 7(f) and 7(i) exhibit that the local and average shear stress is the upsurge for increasing values of , since an enhancement in portion causes an accumulation in the fluids’ thermal conductivity. In the 3D graph, Figure 7(j) exemplifies that the flow profiles decrease with growing values of the magnetic fields. Figures 7(k) and 7(l) show that for rising values of , the local and average shear stress in 3D graphs increases.
4.2. Influence of Prandtl Number
Figure 8(a) illustrates that the velocity profiles increase and then decline for increasing values of . The reason is that lesser value is equivalent to the rise in the thermal conductivity of the fluid, and it also falls very quickly for higher values of which creates high viscosity in the boundary layer. Figure 8(b) demonstrates that the thermal profile increases in the region and then falls for growing values of . Temperature gradients for influenced acceptable quantities of , 1.38, and 7.2 which are significant to salt water, ammonia, and seawater (at 20°C), respectively, and they associate with salt water and ammonia. Also, we see that increasing lessens thermal diffusivity; heat transmission capacity substantially reduces as thermal diffusivity lowers, resulting in a decline in the temperature distribution. The increased is proportional to reduced thermal conductivity. As a result, concentration profile rise shown in Figure 8(c). Figures 8(d) and 8(g) reveal that local and average Nusselt number declines for rising values of (Tables 6 and 7), which creates the reduction in thickness of the thermal boundary layer, as well as an overall lessening of the average temperature drop inside the boundary layer.
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The local and average Sherwood number losses () and then upsurges for mounting values of , which are shown in Figures 8(e) and 8(h) (Tables 8 and 9). Heat distributes gradually, and the thermal boundary layer is lower for a more significant Prandtl number, whereas the reverse scenario is shown at lower values. Figures 8(f) and 8(i) reveal that local and average shear stress decreases for upgrading values. Enlarging , thermal diffusivity diminishes during fluid velocity augmentations. A 3D graph comparison of the local and average Sherwood number of is shown in Figure 8(j).
4.3. Influence of Porosity
Figure 9(a) illustrates that the flow profiles rise for growing values of the porosity parameter . It arises due to the rise permeability of the medium, and the fluid motion is subsequently accelerated. Figure 9(b) illustrates the effect of porosity parameters on temperature, which leads to the rise in temperature profiles (), and the temperature profiles decrease due to enhancement of . Also, it is seen that the porosity parameter strongly affects velocity profiles compared to temperature profiles. Figure 9(c) shows that the material profiles rise with rising values of . Because the porous medium slows down the motion of the fluid, as a result, mass transfer rises. Figures 9(d) and 9(g) reveal that local and average Nusselt number declines for increasing values of . Figures 9(e) and 9(h) expose local and average Sherwood number reductions for growing values of . Figures 9(f) and 9(i) reveal local and average shear stress decrease for rising values of (Tables 10 and 11). It is true that when the permeability parameter’s values increase, the tightness of the porous medium’s resistance to flow diminishes, which in turn causes the fluid’s velocity to increase. Figure 9(j) exemplifies that the flow profiles upsurge with rising values of the porosity parameter in the 3D graph.
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4.4. Influence of Eckert Number
Figure 10(a) shows that the flow profiles decrease () owing to rises in reducing the driving force to heat transfer to the kinetic energy of the flow; that is, there is no effect of on velocity profiles near the plate (Table 12). Figure 10(b) exposes thermal profile declines for rising values of . The accumulation of heat energy in liquid happens due to the fact that frictional heating arises. Consequently, the fluid flow rate increases, and the heat transmission rate falls. As a result, the thermal profiles decrease. The effects of on material profiles are observed in Figure 10(c). The concentration profiles increase with growing values of . It allows energy to be stored in the fluid, which creates frictional heating; for this reason, the concentration profiles increase. Figures 10(d) and 10(g) reveal that local and average Nusselt numbers rise for increasing values of . In Figures 10(e), 10(h), 10(f), and 10(i), the increase in the viscous dissipation term (Eckert number ()) is perceived to decline the local and average Sherwood number as well as shear stress. Materially, the rise in Eckert number causes the heat energy inside the fluid layer to increase. Due to the drop in flow regimes, the heat energy formed by the Eckert number is not conserved, and there is no assurance of frictional heating.
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4.5. Influence of Schmidt Number
To be accurate, the typical values of Schmidt number () are preferred for hydrogen (), ethyl ether (), and toluene () at 25°C and 1 atm, which denotes chemical species dispersing in the most prevalent aspect. Figures 11(a)–11(c) exhibit characteristic behavior of flow, thermal, and material profiles for rising quantities of while maintaining the other parameters constant. It can be shown in Figures 11(a) and 11(b) that the flow and thermal fields increase owing to the enhancement of . Schmidt number measures the relative efficiency of momentum and mass transmission through diffusions in the hydrodynamic and material boundary layer (BL). Figure 11(c) depicts the influence of the Schmidt number on concentration profiles and see that the material profile upsurges with rising values of (Table 13). It is a fact that the rising effect tends to decline the boundary layer and concentrations buoyancy effects. In this case, the flow of fluid diminishes, and the rate of concentration increases. Figures 11(d) and 11(g) reveal that local and average Nusselt numbers rise significantly for growing values. Figures 11(e) and 11(h) illustrate the local and average Sherwood number rise for increasing values of . Otherwise, the rate of mass transmission at the plate drops for high mass diffusivity. Figures 11(f) and 11(i) reveal local and average shear stress decreases for upgrading values. The impact represents the ratio between momentum and mass diffusivity. The flow and material profiles are seen to decline as rises. As a result, the material buoyancy effects lessen, which lowers the fluid velocity. Figure 11(j) shows the consequence of the Schmidt number on thermal profiles in 3D graphs.
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4.6. Comparison
The local Nusselt number acts on the enlargement of heat flow at any point, and the average Nusselt number is significant at all points. So, the average Nusselt number is equal to the local Nusselt number in these circumstances for the consequences of several factors. The local Sherwood number acts on the development of mass transfer at any point, and the average Sherwood number is substantial at all points. So, the average Sherwood number is equivalent to the local Sherwood number for the effects of numerous parameters. In these cases, local and average skin friction is shown to have identical behaviors for the impacts of rising parameters. The consequent table (Table 14) presents a qualitative comparison between the described work and several researchers from the literature studies.
This research is aimed at finding the numerical solution for an MHD heat and mass transfer flow that is viscous, electrically conducting, incompressible, radiating, and flows over a permeable plate. The BL heat absorption, radiation, chemical reaction, and Soret effect-based flow of MHD fluid through a semi-infinite vertical permeable moving plate were examined by Rao et al. [32]. Ali et al. [33] investigated MHD heat and mass transfer portents using magnetic field stimulation along a vertical plate. The effect of Sherwood number, Nusselt number, and skin friction on MHD radiative mass transfer flow from an inclined vertical plate with a heat source and sink was investigated by Sambath et al. [34].
5. Concluding Remarks
The numerical solutions of MHD free convection heat and mass transfer fluid flow over a vertical permeable plate with thermal radiation and heat generation are analyzed depending on the tabular and graphical implications drawn previously. The study dispensed with an FDM explaining approach with time-field contemplation, i.e., for the inconsistent results. This analysis brings out the following conclusions with engineering inquisitiveness: (i)The velocity profile decreases for rising values of , , and and increases with rising values of and (ii)The temperature profile upsurges owing to the various values of , , , and and decreases for (iii)The concentration profile increases with rising , , and values and decreases for and (iv)The local and average skin friction rises for rising values of and . Conversely, it declines with growing values of , , and (v)The local and average Nusselt number increases owing to the different values of and . In contrast, it decreases with rising , , and values(vi)The local and average Sherwood number increases due to the different , , and values. In contrast, the local and average Sherwood number decreases for increasing values of and
6. Future Research
Numerical analysis of time-dependent oriented magneto-convective thermal-material transport across a vertical permeable plate is the subject of our research. The following recommendations can be drawn in future research with applicability from this research: (i)Considering the influence of Hall current on the inclined plate with the flow direction of the flown flow(ii)Considering the influence of Hall current on the flat plate(iii)Considering the pointing vector when electric and magnetic fields are present(iv)Considering the rotating magnetic field without the radiative parameter
Nomenclature| : | Applied uniform magnetic field () |
| : | Concentration at the plate () |
| : | Concentration outside the boundary layer () |
| : | Local Nusselt number |
| : | Local Sherwood number |
| : | Local shear stress |
| : | Average Nusselt number |
| : | Average Sherwood number |
| : | Average shear stress. |
| : | Rosseland mean absorption coefficient |
| : | Dynamic viscosity () |
| : | Stefan-Boltzmann constant |
| : | Dimensionless time. |
Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.
Disclosure
This research was performed as part of the Ph.D. requirement of the first author, as he is a Ph.D. student of Bangladesh University of Engineering and Technology, Bangladesh.
Conflicts of Interest
The authors declare that they have no conflicts of interest.