Nanofluid Layer Research Articles

Instability analysis of vibrated thermo-convection in Casson nanofluid suspension

This work is motivated by the importance of vertical vibration in nanofluids suspension, because of its wide applications in heat exchangers from one fluid to another, controlling the mixing in microvolumes, pharmaceutical industry, and engineering. The current study analyzes the effects of high-frequency vertical vibration on a horizontal Casson nanofluid layer heated from below saturated between rigid-rigid, rigid-free, and free-free boundary conditions. Field equations are derived by using time-average method, which describes the vibrational thermo-convection. These field equations are solved by utilizing linear stability analysis and Galerkin technique to obtain the thermal stability curve. By using this curve, the impacts of vertical vibration and physical governing factors on temperature profile are discussed. High-frequency vertical vibration is observed to have a stabilizing effect on Casson nanofluid suspension, thereby reducing thermo-convective heat transfer from one fluid to another. Stability threshold of vibrated suspension is increased approximately as [Formula: see text] and [Formula: see text] when [Formula: see text] and [Formula: see text], respectively. The significance of Brownian motion and thermophoretic force on convective heat transfer with vertical vibration is discussed. The resisting nature of Casson nanofluid on vibrational convective heat transfer is also tabulated.

Electroconvection in Rotating Jeffrey Nanofluid Saturating Porous Medium: Free–Free, Rigid-Free, Rigid–Rigid Boundaries

The impact of rotation and the boundaries on the initiation of convective instability in a rheological nanofluid layer heated beneath saturated by a porous media with the inclusion of an AC electric field (vertical) is studied employing linear stability analysis. The stationary convective stability of rheological nanofluid is customarily established utilizing Buongiorno model for nanoparticles and Jeffrey model for rheological behavior of regular fluid. The Buongiorno model deployed for nanofluids incorporates the influence of thermophoresis and Brownian motion. Using the normal mode technique, the set of coupled differential equations is solved analytically for both stress-free boudaries and numerically by using the Galerkin-type Weighted Residual Method (GWRM) for top-free, bottom-rigid and rigid–rigid bounding surfaces. The numerical computed values of stationary thermal Rayleigh number are presented graphically for three distinct combinations of boundary conditions. The Taylor number accounting for rotation parameter, Jeffrey parameter, and nanofluid Lewis number delay the start of stationary convection, whereas electric field and concentration Rayleigh number destabilize a system for three groups of boundaries. The bottom-/top-heavy nanofluids are found to be more/less stable. Rigid–rigid boundaries augment the stability in a more pronounced manner than that of the stress-free and rigid-free boundaries. The conditions for non-occurrence of over stability are also derived. This study is of great significance in many metallurgical processes including megma flow, deep convective chimneys, polymer solutions, microfluidic devices and blood flow in micro circulatory systems. An excellent coincidence is found admist present paper and the earlier published work.

Skin‐Inspired Nanofluid‐Filled Surfaces with Tunable Icephobic, Photothermal, and Energy Absorption Properties

AbstractIce buildup can significantly and negatively impact system performance in various industrial sectors, and has remained a persistent challenge for decades. Many compliant materials exhibit excellent de‐icing performance but are easily eroded by impacts from supercooled water droplets, sand, dust, and debris. A composite panel inspired by animal skin, consisting of a facesheet protecting a nanofluid layer beneath, which exhibits durable anti‐icing and tunable photothermal properties is proposed. The viscous liquid layer beneath the facesheet increases flexural rigidity, preventing large deflections and increasing deformation resistance, which alters ice's adhesion to the surface. The non‐uniform fluid pressure exerted by the viscous nanofluid‐filled composite panels facilitates ice detachment, resulting in ice adhesion strengths as low as τice ≈ 10 kPa. Further, by altering the fluid properties, different additional functionalities can be endowed to the system. Incorporating fumed silica in a fluid‐filled composite panel results in rheopectic behavior, and this doubles their impact resistance when the shear thickening properties are properly tuned. Additionally, the combination of a transparent facesheet and a solar light absorbent nanofluid allows for tunable photothermal properties, further enhancing the anti‐icing performance of the system. This durable and tunable nanofluid‐filled composite panel shows great promise as a multifunctional de‐icing material.

Electrohydrodynamic instability in dielectric rotating Oldroydian nanofluid layer

The influence of rheology on the initiation of thermal convection in a rotating nanofluid layer heated beneath with the inclusion of a vertical alternating current (AC) electric field is studied by employing linear stability analysis in which bounding surfaces are taken as stress-free. The stationary and oscillatory convective stability of the rheological nanofluid is customarily established utilizing the Buongiorno model for nanoparticles and the Oldroyd model for the rheological behaviour of the regular fluid. The Buongiorno model deployed for nanofluids incorporates the impact of thermophoresis and the Brownian motion. The eigen-value problem is solved for exact solutions analytically by using single term Galerkin technique and the expressions of the thermal Rayleigh number for the start of both stationary and oscillatory convection for both bottom-heavy and top-heavy nanoparticles configuration are obtained and are presented graphically.

Magnetohydrodynamic mixed convection in lid-driven curvilinear enclosure with nanofluid and partial porous layer

The current research numerically investigated the inclined magnetic field effects on the combined forced and natural convection in lid driven curvilinear cavity filled with Cu-H2O nanoliquid and a partial porous layer. The complex cavity is partially filled with a porous layer about the lower half and heated with a constant heat source. The entire cavity is occupied with Cu-water nanoliquid. The upper horizontal wall is at a cold temperature and moving towards the right with a constant velocity. The geometry is subjected to an inclined magnetic field. The derived mathematical models are computed numerically using the FEM-based tool. The thermal behavior is assessed through a range of variables, such as Richardson number (0.1 to 10), Darcy number (10 -5 to 10 -1), Reynolds number (30 to 200), Hartmann number (0 to 60), γ (0 to 60°), and nanoparticle concentration ϕ (0.0 to 0.06) at constant Prandtl number, Pr = 6.2, and porosity, ε = 0.4. The main findings indicate that heat transfer inside the cavity rise with the increase of Ri, Re, ϕ, and Da numbers, while decreasing with the rise of the MHD strength. Also, at a low Reynolds number, Re = 30, the value of Nuavg only increased by 18% with the increases in Ri number from 0.1 to 10; however, the increase in Nuavg increased to 64% with a high Reynolds number, Re = 200.

Casson Nanofluid Instability with Viscosity and Conductivity Variation Using Brinkman Model

The present work investigates the onset of convective instability of a non-Newtonian Casson nanofluid layer saturating a porous medium. Conductivity and viscosity are taken to be linear functions of nanoparticle volume fraction and Darcy-Brinkman model is used to modify the momentum equation. It is assumed that all the physical variables undergo a small disturbance on the basic solution and the normal mode technique is used to convert partial differential equations into ODE’s to get the expression of thermal Rayleigh number. Darcy parameter, non-Newtonian fluid property and conductivity variation parameter are coupled together leading to a significant increase in the stability of the layer. Numerical computations are carried out for various base fluids (water, oil, blood, glycol) under different porous phases (glass wool, limestone, sand) for metallic and non-metallic nanoparticles (copper, Iron, alumina, silicon oxide) using the software Wolfram Mathematica (version 12.0). The novelty of the work lies in the fact that the conductivity variation pattern for porous media is established as glass wool < limestone < sand and for base fluids as water < blood < glycol < oil. Maximum conductivity variation is observed for copper-oil nanofluid with sand as porous medium and glass saturated with alumina-water nanofluid shows the minimum variation. Oscillatory mode is found to dominate the instability state for bottom-heavy fluid layer. Darcy parameter stabilizes the fluid layer while porosity effects are destabilizing. Metals are found to be more stable as compare to non-metals.

Natural convection in a square cavity partially filled with porous medium and nanofluid using Buongiorno's model

Natural convection is investigated in a square cavity divided in three layers, nanofluid at the middle and the upper and lower parts for porous layer. The cavity is heated from the left and cold from the right at constant temperature Th and Tc respectively. The side walls are well insulated. The Buongiorno’s model was used to evaluate the distribution of nanoparticles and takes account the Brownian and thermophoresis motion. The governing equations are solved by the Galerkin finite element method. The governing parameters are Rayleigh (103≤ Ra ≤ 106), porous layer thickness (0.3 ≤ Lp ≤ 0.05).The result shows that increasing buoyancy forces reinforce circulation flow in the nanofluid layer than the porous layer, the decrease effect of porous layer thickness improve considerably the convective heat transfer. The heat and mass transfer are enhanced.

Study of Heat and Mass Transfer in a Rotating Nanofluid Layer Under Gravity Modulation

In this paper we investigate the effect of gravity modulation and rotation on thermal instability in a horizontal layer of a nanofluid. Finite amplitudes have been derived using the minimal Fourier series expressions of physical variables in the presence of modulation and slow time. Here we incorporates the layer of nanofluid with effect of Brownian motion along with thermophoresis. Heat and mass transfer are evaluated in terms of finite amplitudes and calculated by Nusselt numbers for fluid and concentration. It is found that, gravity modulation and rotation can be used effectively to regulate heat and mass transfer. This modulation can be easily felt by shaking the layer vertically with sinusoidal manner. The numerical results are obtained for amplitude of modulation and presented graphically. It is found that rotation and frequency of modulation delays the rate of heat and mass transfer. This shows that a stabilizing nature of gravity modulation and rotation against a non rotating system. A comparison made between modulated and unmodulated and found that modulated system influence the stability problem than un modulated system. Similarly modulated system transfer more heat mass transfer than unmodulated case. Finally we have drawn streamlines and nanoparticle isotherms to show the convective phenomenon.

Free Electrothermo-Convective Instability in a Dielectric Oldroydian Nanofluid Layer in a Porous Medium

For the last few years, thermal instability of non-Newtonian nanofluids becomes a prominent field of research because it has various applications in automotive industries, energy-saving, nuclear reactors, transportation, electronics etc. and suspensions of nanoparticles are being developed in medical applications including cancer therapy. In this paper, a free electrothermo-convective instability in a dielectric nanofluid layer in a porous medium is studied. An Oldroyd’s constitutive equation is used to describe the behaviour of nanofluid and for porous medium, the Darcy model is employed. The equation of conservation of momentum of fluid is stimulated due to the presence of an AC electric field, stress-relaxation parameter and strain-retardation parameter. The stability of the system is discussed in stationary and oscillatory convections for free–free boundaries. For the case stationary convection, it is found that the Oldroydian Nanofluid behaves like an ordinary nanofluid as the stationary Rayleigh number is independent of the stress-relaxation parameter, the strain-retardation parameter and Vadasz number. The effect of stress-relaxation-time parameter, strain-retardation-time parameter, Vadasz number, nanoparticles Rayleigh number, modified diffusivity ratio, medium porosity, Lewis number and electric Rayleigh number examined numerically and graphs have been plotted to analyse the stability of the system. It is observed that the electrical Rayleigh number has destabilizing influence whereas nanoparticles Rayleigh number, porosity and modified diffusivity ratio have stabilizing effect on the system. The oscillatory convection is possible for the values of the stress-relaxation parameter less than the strain-retardation parameter for both top-heavy/bottom-heavy distributions of nanoparticles.

Thermal instability analysis in magneto-hybrid nanofluid layer between rough surfaces with variable gravity and space-dependent heat source

The onset of thermal instability with hybrid nanoparticles Al2O3–Cu in nanofluid is investigated with the combined effects of variable gravity, variable heat source and Lorentz force in a porous medium. Its applications are in many areas like chemical engineering, geophysics, astrophysics, etc. Based on literature, many gravity variations are assumed in the present analysis, along with a space-dependent heat source/sink parameter that varies along the width of the channel. The finite difference-based Lobatto IIIa method has been applied to solve the system under no nanoparticle flux and rough boundary conditions, and approximate analytical results are generated for some special cases. The roughness parameters ([Formula: see text]), Darcy number (Da), gravity variation function ([Formula: see text]), and Chandrasekhar number (Q) delay the onset of convection and thus stabilize the system. It is also observed that an increase in the Lewis number Le, power index in variable heat source, and the nanoparticle Rayleigh concentration number Rn decreases the critical Rayleigh number [Formula: see text] which destabilizes the system, and increases the critical wave number, which enlarges the convection cell size. In the case of exponential variation ([Formula: see text]) in the gravity variation parameter, the system becomes stabilized due to a delay in the onset of convection. In addition, we have considered multilayer perceptron-artificial neural network (MLP-ANN) computation to predict the critical Rayleigh number as per function of important controlling parameters. The data set of 625 observations is chosen keeping 70% for testing, 15% for training and 15% for validation using efficient Levenberg−Marquardt back propagation algorithm with optimal accuracy measures i.e., root mean square deviation (RMSE), root mean relative error (RMRE) and [Formula: see text] (coefficient of determination). Finally, the regression plots are drawn that correlate, target and output data.

Effect of magnetic field on electroconvection in a thin layer of magnetic nanofluid

It is shown that the external magnetic field (of the strength < 10 kA/m) parallel to the electric field (DC and AC) reduces the electroconvection development threshold voltage and the time of electroconvection development (up to 50 %), and creates a more branched pattern of electroconvective flows in a layer of magnetic nanofluid. The magnetic field perpendicular to the electric field increases the electroconvection development threshold (up to 15 %) and leads to electroconvective pattern degeneracy into a system of strips parallel to the magnetic field. It is demonstrated that the critical voltage increases with increasing magnetic nanofluid layer thickness and voltage frequency.

Unsteady Finite Amplitude Magneto-Convection of Oldroyd-B Nanofluids with Internal Heat Source

This work presents a numerical and an analytical review of analysis of the convective phenomenon in a non-Newtonian nanofluid layer with the applied vertical magnetic field and having an internal heating source. Buongiorno model is used to examine the convective instability considering the impacts of thermophoresis, Brownian diffusion, and viscoelasticity of the nanofluid. The effect of significant parameters concerning stability is visualized through graphs and further interpreted. For the non-linear study, the fundamental PDEs are converted into non-linear simultaneous autonomous ODEs. The solutions are computed by taking the help of the software Mathematica. Nusselt number and Sherwood number are graphed for numerous parametric situations to offer a clear outlook of heat and mass transfer rate. The magnetic field parameter stabilizes the system and diminishes heat and mass transfer. Elevating the internal heat parameter promotes heat and mass transfer significantly. Viscoelasticity of the fluid affects prominently since non-Newtonian fluid yields lower heat and mass transfer coefficients than Newtonian fluid due to advancement of the convection.

Influence of particle deposition on heat transfer characteristics for nanofluid free impinging jet: A numerical study

Based on the two-body collision model, a nanoparticle collision, deposition and peeling model is established to describe the nanoparticle deposition process during SiO2-water nanofluid jet impinging on a heated copper column. The model is loaded with the Euler-Lagrange multiphase model in Ansys Fluent 19.1, and its accuracy is verified by comparing with the experimental data. Then the nanoparticle deposition processes during nanofluid jet impinging are studied with different inlet Reynolds numbers (Re), nanofluid volume fractions and impact heights (H/D). Result shows that the amount of nanoparticle deposition increases with the increasing nanofluid volume fraction, and it has a tendency of first increasing and then decreasing with the increasing inlet Reynolds number and the impact height, which reaches a maximum value when Re = 8849 and H/D = 4. Result also shows that it is easier to deposit at the junction between the impact zone and the wall jet zone with a deposition amount approximately 2 times of that at the outlet. A nanoparticle thermal resistance layer and a high-density nanofluid layer are formed in the near-wall region, and velocity slip between phases in the layer could reach 2.824m/s, which significantly enhance the base-fluid’s micro-flow intensity and the particles’ movement, thus strengthening the momentum exchange and energy exchange between phases and wall. The maximum heat transfer coefficient could reach 27857.4 W/(K·m2), and the average heat transfer coefficient has a 67.9% increment with 3% SiO2-water nanofluid volume fraction.

Linear and weakly nonlinear investigation in thermal stability analyses of MHD convection utilizing non-Newtonian nanofluid in rotating frame of reference

In this column, the stability of a non-Newtonian nanofluid (Al2O3-EG) layer subjected to chemical reaction, rotation and magneto-convection is investigated. Buongiorno's two-phase partial differential equations (PDEs) based model with two dominant slip mechanisms, is used to perform linear and non-linear stability analyses. The boundary conditions used for linear theory are rigid-rigid and rigid-free while free-free boundaries are used to explore the non-linear case. In linear theory, both Galerkin weighted residual technique and boundary value solver are used to solve normal mode equations and neutral curves have been compared. Using weakly non-linear theory, non-linear partial differential equations are converted into system of first order differential equations by minimal truncated Fourier series which is further solved with Runge Kutta Dormand–Prince method. The results depicting the effect of thermal Nusselt number and nanoparticle Nusselt number are strategized for both steady and unsteady case. Results indicate that four controlling parameters () delay the convective motion in nanofluid layer while concentration Rayleigh Number () accelerates it. The behavior of streamlines, iso-therms and iso-nanohalines shift from conduction to convection mode for large Rayleigh number and time t.

HEAT AND MASS TRANSPORT IN A NANOFLUID LAYER USING A THERMAL NONEQUILIBRIUM MODEL CONFINED WITHIN A HELE-SHAW CELL UNDER THE EFFECT OF GRAVITY MODULATION

The local thermal nonequilibrium (LTNE) condition is the temperature difference between the base fluid and the nanoparticle. In the present research article, linear analysis was done to know about the onset of convection in the system, and a weakly nonlinear stability analysis was done to know about heat and mass transport in the system for both the unsteady and steady case. Here we have taken temperature to be constant and nanoparticle flux to be zero at the upper and lower boundaries of the system. The normal mode technique is used for linear analysis, and the truncated Fourier series method is used for nonlinear analysis; plot streamlines, isotherms, and isohaline are used to visualize the conduction, convection, and steady state. We found that the behavior of Hele-Shaw cell is the same in the case of LTNE and local thermal equilibrium (LTE). The effect of Hele-Shaw number, interphase heat transfer coefficient, modified thermal capacity ratio, thermal diffusivity ratio, amplitude, and frequency of modulation on the onset of convection, heat, and mass transfer are depicted graphically. We found that the effect of LTNE can be seen only for the intermediate values of the interphase heat transfer coefficient, and this region is called the LTNE region. We also discuss the result of thermal Nusselt number, streamlines, and isothermals of fluid and particle phase for steady case and plot the graphs with respect to the Hele-Shaw cell Rayleigh number. Rate of heat transfer for the particle phase is higher than the fluid phase for both the unsteady and steady state. In this research paper we find the result for both LTE and LTNE conditions with unsteady and steady cases, while in the previous study we analyzed only for the LTE condition.

ROTATING CASSON NANOFLUID CONVECTION FOR Au, Ag, CuO, AND Al2O3 NANOPARTICLES EMBEDDED BY DARCY-BRINKMAN POROUS MEDIUM

The present paper investigates convection in a Casson nanofluid layer in porous medium under the influence of Coriolis force using Darcy-Brinkman model. The analysis is carried out using linear stability theory, normal mode technique, and one term Galerkin type weighted residual method for various metallic and non-metallic nanoparticles. The outcomes are compared with previously published results, and fine agreements are noted for the permissible range of parameters. Numerical simulation for porous media is carried out for blood (Casson fluid) using the software Mathematica to make the investigation helpful for practical applications. The effect of porous medium, rotation, Casson parameter, and nanoparticle parameters is discussed. Interestingly, it is found that though Casson fluids are more stable as compared to regular fluids, the Casson parameter itself has a destabilizing effect on the system. The main objective of the study is to consider the impact of Coriolis force on a Casson nanofluid layer with metallic and non-metallic nanoparticles. This effect is of paramount importance in geophysical studies, particularly in the extraction of crude oils. Further, by increasing the rotation parameter, the axial velocity of the blood-based Casson fluid increases, which may help in the treatment of stenosis of arteries and throat. The importance and novelty of the study is the fact that Coriolis force can stabilize various nanoparticle-based Casson fluid layer systems, which were otherwise unstable. As far as metallic and non-metallic nanoparticles are concerned, the stability pattern followed by metallic nanofluids is iron-blood &amp;#62; copper-blood &amp;#62; silver-blood &amp;#62; gold-blood, and for non-metallic nanofluids is silica-blood &amp;#62; alumina-blood &amp;#62; titanium oxide-blood &amp;#62; copper oxide-blood.

On the stability and dynamic transitions of the nanofluid layer heated from below

In this paper, the stability and the type of dynamic transitions of the nanofluid layer heated from below are studied. Firstly, the linear stability of the basic state of the nanofluid layer is investigated. Theoretically, we prove that the basic state is going to remain stable as the Rayleigh number small enough. Numerically, we show that the basic state will lose its stability and become unstable when the Rayleigh number exceeds a critical value. Secondly, the dynamic transition related to basic state instability is studied. We show that a parameter called transition number plays an important role in determining the type of the phase transition. It is more accurate to say that if the sign of the real part of the transition number is negative (positive) then the type of the phase transition is continuous (catastrophic) transition. Finally, we use numerical experiment to determine the transition types under the specifying control parameters cases. Our numerical experiments show that the transition number always has a negative real part which means that the phase transition can only be continuous transition.

Rotating Casson nanofluid convection for Au, Ag, CuO and Al2O3 nanoparticles embedded by Darcy-Brinkman porous medium

The present study examines convection in a Casson nanofluid layer in a porous media under the effect of Coriolis force using Darcy-Brinkman model. For a variety of metallic and non-metallic nanoparticles, the analysis is conducted by utilizing the linear stability theory, normal mode approach, and one term Galerkin type weighted residual method. When current numerical findings are compared to those that have already been published, good agreements are found for the permitted range of parameters. Blood (Casson fluid) is numerically simulated for porous media using the Mathematica software to make the analysis valuable for practical applications. Top-heavy configuration of nanoparticles is found to lead to a stationary mode of convection. The effect of porous medium, rotation, Casson parameter and nanoparticle parameters is discussed numerically. Interestingly, it is found that though Casson fluids are more stable as compared to regular fluids but Casson parameter itself has a destabilizing effect on the system. The really important and novel result of the study comes out as the fact that Coriolis force can stabilize the gold-nanoparticle-based Casson fluid layer system which is otherwise totally unstable. As far as metallic and non-metallic nanoparticles are concerned; the stability pattern followed by metallic nanofluids is iron-blood>copper-blood>silver-blood>gold-blood and for non-metallic nanofluids is silica-blood> alumina-blood> titanium oxide-blood>copper oxide-blood.

UNSTEADY TRIPLE-DIFFUSIVE CONVECTION EMBEDDED WITH DARCY-BRINKMAN THREE-TEMPERATURE MODEL

The theory of binary nanofluid layer heated and soluted from below under the effect of local thermal non-equilibrium has been investigated by applying the technique of superposition of basic feasible modes with one-term Galerkin residual method. The so-called Darcy-Brinkman model for the top-heavy distribution of nanoparticles has been employed. A three-temperature local thermal non-equilibrium (LTNE) model, assuming one-temperature field for the solid matrix, one for the base fluid, and one for the suspended nanosized particles, is employed, incorporating the effects of Brownian and thermophoretic diffusions. Numerical computations are carried out with the software Mathematica (version 12.0). The novelty of the problem lies in the fact that destabilizing influence of nanoparticles and solute is countered with stabilization due to the presence of Darcy-Brinkman porous medium. Further, it has been observed that the two LTNE parameters namely, Nield parameter for particles and modified solute thermal capacity ratio, have destabilizing effects which are balanced by the other two parameters, viz. Nield parameter for solute and modified thermal capacity ratio for particles. The impact of nanofluid parameters is found to destabilize this top-heavy configuration of nanoparticles. Due to the consideration of Darcy-Brinkman model, Darcy number came into existence, which postpones the onset of instability. Similar is the effect of porosity and modified thermal diffusivity ratios for the particles as well as the solute.

Steady Magnetohydrodynamic Flow of Cu–Al2O3/Water Hybrid Nanofluid Over a Yawed Cylinder

This study presents non-similar solutions for the magnetohydrodynamic hybrid nanofluid copper-alumina/water flow over an infinite yawed cylinder, featuring an emphasis on entropy generation owing to heat transfer, fluid friction, and joule heating. Non-similar transformations are used to convert non-linear governing equations and boundary conditions into a non-dimensional form, which is subsequently linearized using the quasi-linearization approach. Implicit finite differentiation is used to solve the equations that arise. The influence of viscous dissipation is considered and entropy generation analysis is done for various values of yaw angle, magnetohydrodynamic parameter and viscous dissipation parameter. The results show that when the magnetic field is increased, the ordinary separation is delayed. The thermal boundary layer of the hybrid nanofluid copper-alumina/water is found to be thicker than the thermal boundary layer of the nanofluids copper/water and alumina/water as well as the working fluid water. As the viscous dissipation and magnetic field increase, the overall entropy generation increases. To lower overall entropy generation, the cylinder’s yaw angle must be increased.