Related Boundary Conditions Research Articles

Role of chemical processes and porous media in thermal transport of Casson nanofluid flow: A study with Riga plates

A Riga plate is an electro-magnetic instrument working with anodes and magnets on plates. The Riga plate has numerous advantages in geophysical sciences, the field of engineering, sensors,and astrophysics.The present work investigated the transitory Electromagnetohydrodynamic radiative squeezing unsteady motion of Casson nanofluid through a parallel channel impacted by the Riga plate with endothermic/exothermic chemical processes and porous media. The PDEs transform into non-linear ODEs using the appropriate similarity transformations. The RKF-45 method and Shooting techniques are utilized to compute the solutions to these non-linear ODEs and related boundary conditions. The consequences of non-dimensional parameters on the corresponding profiles are illustrated graphically. And also studied some significant engineering coefficients. The primary findings of the present study are a rise in the thermal relaxation time parameter, temperature increases for the exothermic chemical reaction case, and opposite behavior in the endothermic chemical reaction case. Enhancement in activation energy parameter, the temperature drops for exothermic and increases for the endothermic case. The value of the modified Hartmann number rises, the velocity profile is also increased in the lower plate and the opposite behavior in the upper plate. Increase in Biot number, temperature decreases in the exothermic case and increases in the endothermic case.

Analysis of projection welding in relation to the non-parallelism of electrodes

The article contains the analysis of projection welding in relation to the non-parallel location (non-parallelism) of electrodes. For a thin-walled flat element, e.g., sheet metal with two embossed projections, calculations were conducted for different angles between the upper electrode and the lower electrode. The calculation involved the use of the SORPAS 3D software. The analysis included the distribution of temperature, power density, electrode displacement, the volume of molten metal in the weld nugget, nugget diameters, and energy supplied to the weld. The article presents the comparison of results obtained for various angles between the electrodes of the welding machine. The results of numerical calculations were verified experimentally through technological welding tests and destructive tests (peeling/metallographic). The convergence of the experimental and numerical results was satisfactory. The tests involved a typical element used in the automotive industry, i.e., a nut with two embossed projections in the flat part. The article represents quite an innovative new approach to multiple-projection welding from a numerical calculation point of view. Such an approach allows the researcher to identify the phenomena taking place in the process. The article also presents a new approach to the analysis of multi-projection welding as regards the non-parallelism of electrodes. The results enabled the determination of phenomena taking place in the multi-projection welding process as well as the boundary conditions in relation to which the process became improper (unstable).

Thermo-hydro-mechanical viscoplastic constitutive model for polyester strap reinforcement long-term response

Polymeric materials have been shown to be rate-dependent materials, that is, their response will vary depending on the conditions to which they are subjected. The present work details the formulation, validation and implementation of a viscoplastic constitutive model with stress, strain, temperature, and relative humidity dependencies aimed to simulate the long-term response of polymeric materials, particularly that of polyester. The model is capable of predicting primary and secondary creep, often observed in geosynthetic materials. Both creep mechanisms can be modelled independently if needed. For calibration, a wide data-set of polyester strap reinforcement creep measurements was used. The validation process was done using parameters for load-, product-, and material-specific scenarios. Load- and product-specific scenarios showed suitable agreement between simulated and measured data. The coupled capabilities of the model are shown via variable temperature and relative humidity boundary conditions. Due to lack of data, temperature and relative humidity dependencies represent idealized scenarios. Simulations of stress-relaxation response for constant rate of strain scenarios are also provided. The proposed formulation is aimed at modelling the mechanical response of reinforced soil structures while accounting for the effect of in-air or in-soil conditions to which reinforcement materials can be exposed to throughout the structure’s life-cycle.

Theoretical and experimental transverse vibration analysis of a non-uniform composite helical tidal turbine foil

Recently, tidal energy has gained attention as an attractive renewable source of power generation. In this context, tidal turbine foils must operate in harsh conditions and extremely variable dynamic loads. Considering the expensive dynamic tests required for these large structures, developing validated dynamic models could be valuable for failure prediction and design purposes. In this paper, the free and forced vibration behaviour of the cantilevered part of a non-uniform helical tidal turbine foil made from the composite material is investigated theoretically and experimentally. In this regard, governing vibration equations of the foil with related boundary conditions are presented. The free vibration analysis of the foil is performed by solving a boundary-value problem, where a closed-form solution, based on the mode summation method, for the forced vibration of the foil is employed. Finally, the obtained numerical results (natural frequency and dynamic displacements) are compared with the corresponding results from experiments to validate the vibration equations and the employed solution. Acceptable agreement between numerical and experimental data confirms that the vibration model presented in this study can be employed to predict the dynamic response, parametric study, optimization, and design of the tidal foil without performing costly experiments.

Shear and normal stresses of electroosmotic magnetized physiological nanofluid on curved artery with moderate Reynolds number: application on electroshock therapy

PurposeStudying the shear stress and pressure resulting on the walls of blood vessels, especially during high-pressure cases, which may lead to the explosion or rupture of these vessels, can also lead to the death of many patients. Therefore, it was necessary to try to control the shear and normal stresses on these veins through nanoparticles in the presence of some external forces, such as exposure to some electromagnetic shocks, to reduce the risk of high pressure and stress on those blood vessels. This study aims to examines the shear and normal stresses of electroosmotic-magnetized Sutterby Buongiorno’s nanofluid in a symmetric peristaltic channel with a moderate Reynolds number and curvature. The production of thermal radiation is also considered. Sutterby nanofluids equations of motion, energy equation, nanoparticles concentration, induced magnetic field and electric potential are calculated without approximation using small and long wavelengths with moderate Reynolds numbers.Design/methodology/approachThe Adomian decomposition method solves the nonlinear partial differential equations with related boundary conditions. Graphs and tables show flow features and biophysical factors like shear and normal stresses.FindingsThis study found that when curvature and a moderate Reynolds number are present, the non-Newtonian Sutterby fluid raises shear stress across all domains due to velocity decay, resulting in high shear stress. Additionally, modest mobility increases shear stress across all channel domains. The Sutterby parameter causes fluid motion resistance, which results in low energy generation and a decrease in the temperature distribution.Originality/valueEquations of motion, energy equation, nanoparticle concentration, induced magnetic field and electric potential for Sutterby nano-fluids are obtained without any approximation i.e. the authors take small and long wavelengths and also moderate Reynolds numbers.

Frequency Regulation in Nanocomposite Sandwich Joined Conical-Conical Shells with Open Cell Foam Partially Supported by Pasternak Elastic Foundation Using GDQ

This study investigated the natural vibration of a sandwich conical-conical shell that is partially supported by Winkler–Pasternak foundations. The sandwich system comprises an open-cell foam (OCF) core and laminated composite face sheets reinforced with graphene platelets using functionally graded models (FG-GPLRC). To account for through-the-thickness shear deformations and rotary inertias, the first-order theory of shells is combined with Donnell-type kinematic assumptions. Hamilton’s principle is utilized to establish the general motion equations and related boundary and continuity conditions. The resulting system of equations is discretized using the semi-analytical generalized differential quadrature (GDQ) approach. An eigenvalue problem is formulated to analyze the corresponding mode shapes and vibration frequencies for the shell ends and continuity criteria under various boundary conditions. Parametric experiments are conducted for sandwich conical-conical shells partially supported by Winkler–Pasternak foundations. This study examined the impact of multiple factors on the frequency of a joined shell structure, including the total thickness, FG-GPL face sheet thickness, various boundary conditions, the length of each cone segment, and the Winkler and shear elastic foundation. Notably, this research also analyzed the effects of a partial elastic foundation on the structure’s frequency for the first time.

Nonlocal strain gradient-based dynamic stability of functionally graded piezoelectric nanoshells considering thermo-electro-mechanical coupling effects

In this paper, a nonclassical shell model is utilized to investigate the dynamic stability of functionally graded piezoelectric (FGP) nanoshells considering the thermo-electro-mechanical coupling effects. Also, the FGP nanoshells on elastic foundations are subjected to periodic axial loading. The theoretical formulations are derived by implementing the first-order shear deformation (FSD) shell theory into the nonlocal strain gradient theory (NSGT). Hamilton’s principle is utilized to obtain the equations of motion and related boundary conditions of the present nanoshell model. Moreover, the Mathieu-Hill equations determining the instability regions are presented and analyzed based on Bolotin’s method. Results demonstrate that the external electric voltage, the elastic foundations, the temperature rise, the static load factor, the power-law index and the small-scale parameters have significant influences on the dynamic stability responses of FGP nanoshells.

Application of Modified Couple-Stress Theory to Nonlinear Vibration Analysis of Nanobeam with Different Boundary Conditions

PurposeIn the present study, the nonlinear vibration analysis of a nanoscale beam with different boundary conditions named as simply supported, clamped-clamped, clamped-simple and clamped-free are investigated numerically.MethodsNanoscale beam is considered as Euler-Bernoulli beam model having size-dependent. This non-classical nanobeam model has a size dependent incorporated with the material length scale parameter. The equation of motion of the system and the related boundary conditions are derived using the modified couple stress theory and employing Hamilton’s principle. Multiple scale method is used to obtain the approximate analytical solution.ResultNumerical results by considering the effect of the ratio of beam height to the internal material length scale parameter, h/l and with and without the Poisson effect, υ are graphically presented and tabulated.ConclusionWe remark that small size effect and poisson effect have a considerable effect on the linear fundamental frequency and the vibration amplitude. In order to show the accuracy of the results obtained, comparison study is also performed with existing studies in the literature.

Winding Response under Difference Effective Inductance for Single Phase High Voltage Transformer

Early studies of transformer winding parameters were focused on the determination via its physical dimensions and empirical formulas. In most cases it is divided into several parts namely coil section pairs, coils distance, disc coils diameter and thickness of insulation. Maxwell’s equations are often the solution to the problem, which satisfy related boundary conditions between conductors for mutual inductance and capacitor equations. Such solutions often led to errors and hence its mathematical model. To counter the problem, it was suggested that such approximations must be conducted with experimental model windings at the same time. Frequency domain measurements and time domain measurements can be conducted to effectively determine these parameters. This in turn will investigate the behaviour of transformer winding electromagnetic transient at high frequency. From theoretical point of view, predominantly capacitive winding model often considered to represent its behaviour at high frequency and will give the results of its initial distribution. Under this consideration, a single phase plain winding is considered for investigation. A single rectangular wave was considered to represent infinitive impinge incident wave, injected at one end of transformer winding and the measured response signals of the wavetail were considered for measurement. The experimental response and modelling results were compared and proved to have high agreement between the two.

Diffraction of a pseudo nondiffracting Bessel beam by a circular perfect electromagnetic conductor disk.

This study examined the diffraction of a pseudo nondiffracting Bessel beam by a perfect electromagnetic disk. The geometric optics beam waves were written from the geometry of the problem and related boundary conditions. The diffracted beam waves were derived by utilizing the relation between geometric optics and diffracted waves at the transition boundaries, considering the high frequency asymptotic expression of the scattered wave. The uniform scattered beam waves were expressed in terms of Fresnel functions with the uniform geometrical theory of the diffraction method. Thus, finite magnitudes were read at the transition boundaries. Finally, the obtained uniform expressions were investigated numerically for different groups of parameters.

A concerted experimental and numerical approach for frequency based non-destructive analysis of Bi-directional cracked laminated composite beams

ABSTRACT The effects of single and multiple transverse open cracks on the dynamic properties of woven fibre laminated composite beam (LCB) under free vibration by experimental and numerical approaches are explored in this research work. The experimental modal testing is performed n laminated glass/epoxy composite beams using vibration Fast Fourier Transformation (FFT) analyser system. The finite element simulation software ABAQUS is used as the platform for numerical modal analysis to arrive at the natural frequencies. Within the test domain of modal analysis, the simulated results are finely agreed with the empirical test results. The effects of crack location, relative crack depth, boundary conditions and fibre orientations on the modal frequency of the cracked LCB are explored under free vibration. The results of the study conclude that the maximum decrease in frequencies is observed for 0° ply oriented single and multi-cracked LCB. Furthermore, the results elicit that the presence of crack positioned nearer to the restrained end exhibits more reduction in vibration frequencies for any particular crack depth. Within the frequency domain, the present research approach can be employed as an effective tool for the detection and analysis of crack or crack-like defects in LCB structures in any applied field of engineering.

Natural frequency analysis of bidirectional functionally graded plates based on a refined shear theory using nonconforming finite elements

In this study, we investigate the free vibrations of functionally graded plates using the refined shear deformation theory. These plates have material properties that vary in two directions: the z-axis and the x-axis. The variation follows a bidirectional gradation described by a power law based on the Voigt rule of mixture. The displacement field is characterized by four variables, chosen in such a way that shear strain and stress vanish, and traction is free at the upper and lower surfaces of the plate. This eliminates the need for a shear correction factor, as required in the first-order shear deformation theory. We derive the equations of motion and related boundary conditions using Hamilton’s principle and a finite element approach. The proposed element ensures C1-continuity by including the first derivative of the transverse deflection in the kinematic field. For spatial discretization, we employ a rectangular element with four nodes and two interpolation schemes. Lagrangian shape functions are used for in-plane displacement, while a Hermitian scheme is employed for transverse deflection. This enables us to determine the natural frequencies of the 2D-FG plates. We demonstrate the validity, convergence, and accuracy of the proposed element through illustrative examples and compare it with previous literature. Furthermore, we conduct numerical analyses to examine the effects of transverse shear function, boundary conditions, plate aspect ratio, slenderness ratio, and gradation indices on the natural frequencies. The developed model provides insights into the significance of natural frequencies in the design of various structural elements, including 2D-FG plates.

Prediction model based on artificial neural network and bivariate spectral quasi-linearization method for compressible turbulent boundary-layer flow over a smooth flat surface

The compressible two-dimensional turbulent flow solutions at an arbitrary point in time and space by incorporating the mass, momentum, and energy conservation equations over a smooth flat surface and parallel free stream with unfavorable pressure gradient are studied. The Falkner–Skan transformation is applied to the turbulent boundary-layer equations and related boundary conditions, and the resulting nonlinear coupled system of partial differential equations is solved by the bivariate spectral quasi-linearization method. Moreover, to predict the thermal distribution of the flow, an artificial neural network model has been developed with the Nusselt number as target values. Several plots have been depicted, it is evaluated that the mean squared error value is 6.41 × 10−7, the overall coefficient of determination (R) is 0.997 52, and the average error rate is 0.68% for the said model, indicating the attainment of high accuracy for estimation.

A mesh-free Hermite-type approach for buckling analysis of functionally graded polygonal thin plates

This work aims to establish a developed Meshless process which uses the point interpolation and the Hermite-type point interpolation methods for instability analysis of functionally graded material (FGM) thin polygonal plates. The structure’s material characteristics should gradually change according to the thickness direction. The minimization principle is used to obtain the governing nonlinear static equilibrium differential equations and related boundary conditions. To obtain the discrete weak form, point interpolation method (PIM) is used to approximate membrane components, while Hermite-type point interpolation method (HtPIM) ones are used for flexural components. The critical buckling loads and the associated eigenmodes are obtained by transforming the resulting equations into an eigenvalues problem. To evaluate the validity and effectiveness of the presented methodology, several examples concerning specimens of FGM rectangular and polygonal plates of various geometric planar shapes (L, T and C) subjected to uniaxial and biaxial in-plan loads are studied. The outcomes are contrasted with those of the finite element approach and with some data from the literature. Based on the analysis of the comparative study, the proposed methodology presents a very good agreement with the validated and previously published numerical results.

Nonlinear electromechanical bending of bi-modular piezoelectric laminated beams

In this paper, the nonlinear electromechanical bending of a bi-modular piezoelectric laminated beam is studied based on the principle of minimum potential energy and the Adomian decomposition method. The different tensile-compressive Young’s modulus of the core and piezoelectric layers, and the different tensile-compressive piezoelectric coefficients are considered. The electromechanical governing equations and related boundary conditions are obtained by using the principle of minimum potential energy. The deflection, neutral layer and interlaminar stresses of the beam are solved by the Adomian decomposition method and the iterative method, and verified by the finite element model and Galerkin's method. Results show that the applied voltage and the bi-modular characteristics affect the position of the neutral layer and the interlaminar stresses. Compared with the bi-modular properties of the core layer, the influences of the bi-modular properties of the piezoelectric layer on the neutral layer are relatively unobvious. In addition, the interlaminar stresses between the piezoelectric layer and core layer can be increased or decreased, depending on the relative magnitude of the applied voltage ratio and the bi-modular ratio. The results obtained are helpful for the analysis of the electromechanical coupling mechanism and design of piezoelectric composites and structures with bi-modular characteristics.

Soret-Dufour Effects on Heat and Mass Transfer of Newtonian Fluid Flow over the Inclined Sheet and Magnetic Field

Newtonian fluid is ideal for lubrication purposes because the viscosity of this fluid remains as a function of the shear. Besides, the heat and mass transfer are an important study area in fluid dynamics due to its vast applications in industrial processes. The heat-mass transfer can be defined as the Soret and Dufour effect, which implemented in many industrial applications such as in chemical engineering and geosciences field. In addition, the fluid flow over an extending/compressing sheet has significant industrial applications such as the cooling of continuous strips, glass fibre production, the extrusion of plastic sheets from a die, etc. As a response, this study aims to investigate the impacts of Soret and Dufour parameters on the Newtonian fluid flow over an inclined stretching/shrinking sheet. The methodology of this mathematical model are stated as follow: 1) the transformation of partial differential equations (PDEs) to the ordinary differential equations (ODEs), and 2) The ODEs are solved using bvp4c solver in MATLAB software. The bvp4c solver is a MATLAB program directory that solves general form and multi-point boundary layer problems. The main sections of bvp4c are: 1) The solution of the ODEs, 2) The related boundary conditions that can produce the expected results, and 3) An initial guess to run the bvp4c solver. As a result, the numerical and graphical results show that the Soret effect increases the concentration profile whereas decreases the temperature profile. The vice versa occurrence is true for Dufour effect. The convective mass transfer caused by a temperature gradient is known as thermal-diffusion (Soret) effect. The convective heat transfer produced by concentration differences is known as diffusion-thermo (Dufour) effect. However, since the process of heat and mass transfers are related to each other, the Soret and Dufour effects are able to influence both of this process simultaneously. In conclusion, the convective heat transfer is enhanced by increasing Soret and Dufour number while the convective mass transfer is declined by increasing the two numbers.

Biological transmission in a magnetized reactive Casson–Maxwell nanofluid over a tilted stretchy cylinder in an entropy framework

Biological transmission (or bioconvection) offers a huge room for studying the interplay between microorganisms and fluid dynamics. The understanding of bioconvection is relevant for studying microbial ecology, population dynamics and exploring the behaviour of microorganisms in complex environments. The objective of this research work is to delve into the physical and biochemical aspects of bioconvection in a magnetized Casson–Maxwell nanofluid containing gyrotactic microorganisms. The investigation is conducted on a tilted elongated cylindrical surface, taking into account the presence of entropy generation. Arrhenius activation energy and slip and convective boundary conditions are novel aspects of this research. The current model invokes the impacts of thermophoresis diffusion, and Brownian motion impacts using the Buongiorno model. The Casson–Maxwell fluid model is employed to expound the rheological behaviour of non-Newtonian nanofluids with the migration of gyrotactic microorganisms. The similarity functions are used to convert the model equations and the related boundary conditions into dimensionless form. The insightful numerical results are developed by implementing the ND Solver in Mathematica, providing valuable insights into the velocity, thermal, concentration, and microorganism fields, as well as the rate of entropy generation and other engineering quantities. Outcomes are presented as graphs and tables for further analysis and discussion. The computational findings unravel several significant contributions of influential model parameters. The Lorentz force and porosity are found to create a drag force that deters the fluid pace, while the reverse trend holds for the fluid temperature. Higher activation energy results in a growth in the concentration field. A larger Peclet number leads to a decline in microorganism density. Furthermore, motile microorganisms’ density and swimming speed significantly influence entropy inflation. A 10% increase in magnetic strength results in a 1.47% increase in skin friction for the Casson fluid model and a 1.32% increase in skin friction for the Casson–Maxwell fluid model. This study contributes to understanding bioconvection in reactive Casson–Maxwell nanofluids with gyrotactic microorganisms and sheds light on entropy production in biological systems.

Nonlinear Vibration and Stability Analysis of Rotating Functionally Graded Piezoelectric Nanobeams

Presented herein is an investigation for the nonlinear vibration and stability analysis of rotating functionally graded (FG) piezoelectric nanobeams based on the nonlocal strain gradient theory. The present model can be regarded as a simplified version for the rotating nanowire of biomechanical nanogenerators. The Hamilton principle is used to derive nonlinear equations of motion and their related boundary conditions, which are then discretized to form a set of algebraic equations. Accordingly, the nonlinear vibration frequencies and buckling loads of the nanobeams can be determined by an iterative method. A parametric study of rotational velocity, nonlocal parameter, material length parameter, power-law index, and electrostatic voltage on the dynamic stability behavior of such nanobeams is also presented. In the cantilever case, increasing the nonlocal parameter and material length parameter can result in a stiffness-hardening effect that is unaffected by rotational velocity and the material length parameter to nonlocal parameter ratio. Yet, this has not been reported previously. More importantly, incorporating the effect of geometric nonlinearity on the dynamic responses and stability results of the nanobeams is indispensable. In particular, new observations for the coupling effect of vibration amplitude and power-law index on the electric potential effect are useful for the design of rotating microelectromechanical devices.

Clinical symbiosis of hybrid nanoparticles and induced magnetic field on heat and mass transfer in multiple stenosed artery with erratic thrombosis

This article scrutinizes blood circulation through an artery having magnetized hybrid nanoparticles (silver and gold) with multiple stenoses at the outer walls and erratic thrombus of different radii at the center. In the realm of biomedical innovation, magnetized hybrid nanoparticles emerge as a captivating frontier. These nanoparticles, amalgamating diverse materials, exhibit magnetic properties that engender novel prospects for targeted drug delivery, medical imaging enhancement, and therapeutic interventions. The study was carried out employing modern bio-fluid dynamics (BFD) software. In this iterative procedure, a second-order finite difference approach is used to solve the governing equations with 0.005 tolerance. The experiment is performed on a blood conduit with mild stenosis assumptions, and expressions of temperature, resistance impedance to flow, velocity, wall shear stress, and pressure gradient are generated by employing related boundary conditions. No one has ever attempted to acquire the remedial impact of an induced magnetic field and hybrid nanoparticles on the bloodstream in a tapering artery containing multiple stenoses on the outside walls and multi-thrombus at the center using 3-D bio-fluid simulation. Furthermore, the study's findings are unique, and these computational discoveries were not previously published by any researcher. The findings suggest that hybrid nanoparticles can be used as medication carriers to reduce the impact of thrombosis and stenosis-induced resistance to blood flow or coagulation-related factors.

Scattering and Diffraction Evaluated by Physical Optics Surface Current on a Truncated Cylindrical Conductive Cap

In this study physical optics (PO) surface current is obtained by using the Malyughinetz solution to get the scattered field expression for a truncated cylindrical conductive cap satisfying the related boundary conditions given throughout this paper. This is done by using the inverse edge point method for the transformation from the Malyughinetz solution for the wave diffraction by a half plane to the wave diffraction by a truncated conductive cylinder. This transformation method can be used to examine the diffraction and scattering phenomena for curved surfaces having discontinuities as dealt with in this work. Total scattered field comprising the incident and scattered fields is plotted with respect to the observation angle for some parameters of the problem. The obtained results are examined numerically for the same parameters.