Journal of Computational Applied Mechanics
Volume:53 Issue: 4, Dec 2022

Nanofluids find numerous applications in thermal engineering and industrial processes due to their effective thermal conductivity property compared to regular fluids. A nanofluid consists of containing nanometer-sized particles, called nanoparticles of metals, oxides, carbides, or carbon nanotubes etc. with water, ethylene glycol, and oil etc. serve as base fluids. The present study takes care of effects of Brownian motion and thermophoresis on unsteady Casson fluid flow, heat and mass transfer over a stretching sheet embedded in a porous medium. Moreover, the flow phenomena are subjected to heat source, thermal radiation, viscous dissipation, Joule heating and are associated with the diffusion of chemically reactive nanoparticles to base fluid. These two thermo mechanical aspects draw a little attention of the researchers as reported in literature. The governing equations of flow model admit similarity solution and are reduce to non-linear ordinary differential equations (ODEs) applying suitable similarity transformation and are solved numerically using Runge-Kutta-Fehlberg method with MATLAB code. The interesting outcomes are recorded as follows: The formation of inverted boundary layer, the consequence of flow reversal, is due to overpowering of shearing effect of the rigid bounding surface over the free stream stretching in the absence of suction. The higher magnetic field intensity as well as unsteady flow parameter leads to increasing skin friction coefficient may lead to flow reversal. Hence, regulating these parameters is a suggesting measure. The low Brownian motion in conjunction with high thermophoresis leads to upsurge of thermal energy (hike in temperature profile) near the bounding surface. The presence of nanoparticles considered in the base fluid, deduces the shearing stress at the plate surface is a desired outcome to avoid flow reversal.

The flow of nanofluids over a stretching surface has gotten a lot of attention because of its many uses in industry and engineering. In recent years, heat and mass transfer in magneto hydrodynamic nanofluids has become a focus of research. The steady two-dimensional Magneto hydrodynamic nanofluid flow across a stretched sheet is examined in this study under the effect of radiation and chemical reaction. The similarity transformations which are used to convert the partial differential equations into ordinary differential equations, these equations are solved by Mathematica12.0. On a visual level, the impacts of different dimensionless parameters on non-dimensional velocity, temperature and concentration profiles have been investigated. In several exceptional circumstances, the resulting numerical findings are compared to previously published results and excellent agreement is found.

The method of small perturbation coupled with the regular perturbation method is employed to investigate the effect of time-periodic electric field modulation on electroconvection in a densely packed anisotropic porous layer saturated with a Boussinesq dielectric fluid. The Darcy model is adopted to describe the fluid motion and the dielectric constant is assumed to be a linear function of temperature. The regular perturbation method is used to determine the critical correction Rayleigh number for small amplitude electric field modulation. It is shown that electric field modulation frequency, electrical, porosity, and anisotropic parameters are related to the shift in the critical Rayleigh number and that subcritical convective motion is possible for low frequency modulation of the electric field. The classical destabilizing effect of the dielectrophoretic force associated with the unmodulated, anisotropic dielectric fluid porous layer is only realized for low frequency modulation of the electric field. Furthermore, it is substantiated that anisotropic parameters greatly influence the stability criterion for moderate and large values of the frequency of electric field modulation. The study reveals that time-varying electric fields and anisotropic characteristics of the fluid layer may have implications for the control of electroconvection in heat transfer applications involving dielectric fluid as working media.

Heat pipes (HPs) are used in temperature profile flattening and cooling process of the devices involved in thermal issues. Thermal performance of a HP can be considered as a function of external and internal parameters. This research develops a numerical model with governing equations to analyze likely effects of a magnetic field on the thermal operation of a specific cylindrical HP. In this model, we consider conservation of mass, momentum and energy, in addition to the magnetohydrodynamic (MHD) equations. We use the finite element method (FEM) to solve the system of stated equations. To demonstrate the validity of numerical results, we compare our numerical results with the results of other works in the absence of magnetic field. Additionally, we develop an experimental setup and show that our numerical and experimental results are in good agreement. Our results show that increasing the magnetic flux density from 0 to 0.2 Tesla results in three important improvements on the HP operation: (a) 47% reduction of the temperature difference, (b) reduction of the average temperature and operation pressure, and (c) increasing the uniformity of temperature distribution.

The two-dimensional pulsatile blood flow in tapered stenosis arteries under the effect of a Magnetic field with mass and heat transfer was analyzed by using a new analytical method called the Akbari-Ganji homotopy perturbation method (AGHPM).This technique is based on integrating the Akbari-Ganji and the homotopy perturbation methods. We succeeded in developing the mathematical model studied by researchers Liu and Liu by adding the effect of the magnetic field of blood flow in addition to the effect of mass and heat transfer on it, this developed model has not been studied before. In the two states (absence and presence) of a magnetic field; the axial velocity, the wall shear stress, flow resistance and volumetric flow rate were investigated under the impact of the angle of tapering, the Grashof number, the solutal Grashof number and magnetic field. The results show that in the case of the absence magnetic field there is good agreement with the previous study made by the researchers Liu and Liu, while in the case of the presence magnetic field it is noted that when the magnetic field increases from 2 to 6, the velocity and flow rate decrease, but in contrast the wall shear stress and resistance flow increases. Moreover, the results establish that AGHPM is effective and extremely accurate in determining the analytical approximate solution for pulsatile blood flow in tapered stenosis arteries under magnetic field influence. Furthermore, the graphs of this novel solution demonstrate the validity, usefulness, and substantiality of AGHPM, and are consistent with the results of earlier investigations.

In this paper numerical analysis is carried out to find out the heat transfer performance of Al2O3/Cu nanofluid and Al2O3 nanofluid for different nanoparticle mixture ratios dispersed in water. The Al2O3 and Al2O3/Cu are simulated to flow in between a plain linear pipe with rectangular cross section. The channel is uniformly heated under constant wall heat flux conditions. The computational model is validated with experimental results from a recent literature study for Nusselt number within 7.89 % error and friction factor within 8.55% error. The simulation studies are performed with 0.5 %, 1.0% and 2.0% volume fraction of nano particle in the carrier fluid. The Reynolds number varies with the flow velocity, and ranges from 2000 to 12000 for the present study. The heat flux applied along the tube is ~7955 W⁄m^2 and corresponds to realistic values obtained from literature review. The impacts of the flow Reynolds number, volume fraction and composition of nanofluids on heat transfer characteristics and friction factor are analyzed for the hybrid nanofluid, and compared with the thermal performance of the chosen single-particle nanofluid. The validation of the numerical model has been performed with the published experimental results available in literature. The studies reveal that in comparison to water, the heat transfer coefficients of Al2O3 nanofluid are higher by 2.7%, 5.2%, and 10.9%, while those of Al2O3⁄Cu nanofluid are higher by 4.1%, 8.0%, and 16.2%, respectively, for (nanoparticle) volume fractions of 0.5%, 1.0%, and 2.0%. As compared to other working fluids, 2%Al2O3 shows the highest pressure drop. The thermal performance of the Al2O3/Cu hybrid nanofluid is better to the single-particle Al2O3 nanofluid dispersed in water. The study shows that for any representative value of volume fraction for the single-particle or hybrid nanofluid, the wall-averaged Nusselt number and the pressure drop increases monotonically with the Reynolds number.

The purpose of the current study is to investigate the therapeutic applications of Darcy-Forchheimer flow and mass transfer of hybrid nanofluid (HNF) over a stretching sheet by the influence of magnetic field and chemical reaction. The HNF is the conglomeration of two types of NPs (NPs) copper (metal) and alumina (metallic oxide) with water as regular fluid. Copper NPs act as an anti-biotic, anti-microbial, and anti-fungal agent whereas alumina NPs has wide range of biomedical applications including cancer therapy, biosensing, and immunotherapy etc. Thus, the present model is useful because it may be used to a variety of fields, including biomedicine, microelectronics, biology, and industrial production processes. By introducing the similarity transformations, the governing partial differential equations (PDEs) are transformed into a set of nonlinear ordinary differential equations (ODEs) and then solved numerically with MATLAB bvp4c code by varying numerous operating physical parameters. It is found that higher values of magnetic, Forchheimer and slip parameters decrease the velocity profiles. Slip parameter and chemical reaction parameter has opposite effect on concentration profile. Volume fractions of NPs and slip parameter have opposite effects on skin friction coefficient and Sherwood number.

The article presents Generalized Integral Transform Method (GITM) for the bending analysis of clamped rectangular thin plates. The problem is a boundary value problem (BVP) represented by a fourth order partial differential equation (PDE). Linear combinations of product of eigenfunctions of vibrating clamped thin beams in the in-plane dimensions are used to formulate the sought for deflection function w(x, y) in terms of a double series with unknown generalized deflection parameters cmn. The GITM converts the BVP to an integral equation and ultimately to an algebraic problem in terms of cmn, which is solved to fully obtain as a double infinite series found to be convergent. Bending moments are obtained using the bending moment deflection relations as double infinite series with convergent properties. The solutions obtained for deflection and bending moments at the center and middle of the clamped edges for the two considered cases of uniformly distributed load and hydrostatic load are in agreement with previous results in literature. The effectiveness of the GITM for the clamped plate problem is thus illustrated.

Utilizing hydrogels for sealing devices has attracted the attention of researchers in both academia and industry. The main reason for this attraction is the ability of these materials to absorb surrounding fluid and swelling and the subsequent sealing of the desired portion without any external manipulation. Investigation of the behavior of these materials when implemented as seals is of major importance. This paper studies a rectangular multilayer hydrogel with different material properties numerically by using thermo-mechanical coupled constitutive models available in the literature. Leakage models of elastomeric seals were implemented to examine the leakage of these seals under the pressure of the fluid. The methods are validated through comparison with experiments benchmarked in the literature. After modeling the seals, the mechanism of leakage is investigated, and parameter study of seals considering the cross-linking density distribution of multilayer hydrogel is presented. The findings showed that the ascending and descending property distributions in the studied multilayer hydrogel have a considerable effect on sealing behavior, providing the researchers with an accurate vision of designing such seals.

Although the nonlocal integral (NI) model circumvents the inconsistencies associated with the differential model, it is shown in the present study that the way its nonlocal kernel function is normalized noticeably affects the dynamic response of nanobeams. To this aim, a two-phase nonlocal integral nanobeam model with different boundary conditions and kernel functions is considered and its natural frequencies are obtained using the Rayleigh-Ritz method. Also, the kernel function is normalized via two procedures to see the influence of each one on the vibration characteristics of nanobeam. From the results it is found that kernel normalization has a significant effect on vibration response of nanobeam and therefore must be taken into account. Further, it is found that the results from each normalized model are noticeably different from the other. Furthermore, by comparing the results of continuum NI models with those from atomistic models, it is revealed that for certain normalization schemes a calibrated nonlocal parameter cannot be found due to twofold hardening-softening behavior. Moreover, the effect of kernel type, boundary conditions and mode number is thoroughly studied. The results from current study can shed light on the way of choosing or developing more reliable equivalent continuum NI models for nanostructures.