Journal of Applied and Computational Mechanics
Volume:7 Issue: 1, Winter 2021

The high costs of open-field diesel engines arise from the lack of maintenance of these systems. Thus, the maintenance of this equipment has been treated as a great challenge, as some methods of data monitoring are not possible to be implemented, given the inadequate sensing conditions, plant location, local climate, facilities, even the methods and maintenance routines. In a second step, the labor is not qualified and of sufficient quantity to meet the demand, resulting in a slow and inefficient system. One of the challenges of predictive systems is to inform damage and failures in real time of the operating conditions of these machines and equipment. This work demonstrates the possibility of analyzing and detecting failures in open field predictive systems, using the concepts of vibration and acoustics in artificial intelligence. One of the results of this work demonstrates the robustness of the negative selection artificial immune system algorithm, whose application of the Wiener filter was of fundamental need. The other result demonstrates the versatility of conditioned use both or just one of the concepts between vibration and acoustics, in prognosis and fault detection. Considering the versatility of using these two techniques, it is possible to affirm that, the predictive systems of real time analysis have an effective solution directed to the area and, if implemented, it is of low cost and high efficiency.

The rheological property plays an important role in a free-form extrusion 3D printing process, no rheological model was available in open literature that could effectively take into account effects of both the non-Newtonian viscosity and the concentration of nano/micro particles in a paste. Here a fractal law for non-Newtonian fluids is suggested using a fractal derivative, the law can predict correctly the boundary effect of a viscous flow, and can model effectively the nonlinear velocity distribution across the section. A systematic derivation of a fractal rheological model is suggested using the basic laws in the fluid mechanics, which can provide a deep insight into the two-scale fractal interpretation of non-Newtonian fluids. An experiment was carefully designed to verify the model and to elucidate the relationship between the shear rate and viscosity of the SiC paste. 15wt.%, 25wt.%, 35wt.% and 45wt.% SiC pastes were prepared by using mixing, stirring and ball milling processes. The rheology of the paste can be controlled primarily through the SiC concentration, which affects the fractal order. The fractal model sheds a bright light on a simple but accurate approach to non-Newtonian fluids.

An unsteady boundary layer flow of a micropolar hybrid nanofluid over a stretching/shrinking sheet is analyzed. The nonlinear ordinary differential equations of the problem have been solved using the efficient implicit Runge–Kutta–Butcher method along with Nachtsheim–Swigert iteration technique. For a certain set of parameters, numerical results expose dual solutions with the change of the velocity ratio parameter. The dual solutions are presented in a wide range of the physical parameters. Using a lot of numerical data, the critical values of the velocity ratio parameter, local friction factor, local couple-stress and local Nusselt number for the existence of dual solutions are expressed as a function of the physical parameters. These expressions might be useful for the development of new technology or for the future experimental investigation.

The present work introduces the thermoelastic vibrations of nonlocal nanobeams resting on a two-parameter foundation. The governing equations are formulated for linear Winkler–Pasternak foundation type based on the generalized dual-phase-lag heat conduction and nonlocal beams theories. The nanobeam is subjected to a temperature ramping function. The coupled equations of the problem are formulated and solved by Laplace transform technique. The effects of the nonlocal parameter and different foundation parameters on the field variables are illustrated graphically and discussed. The results obtained are consistent with previous analytical and numerical results.

Aerodynamic drag reduction of tractor-trailer combination trucks is critically important to improve their fuel consumption which consequently results in lower emissions. One practical method to reduce aerodynamic drag of a truck is by mounting drag reduction devices on the truck. This paper presents a numerical study of turbulent flow over a simplified tractor-trailer truck with different drag reduction devices mounted on the truck using the Reynolds Averaged Navier-Stokes (RANS) approach to assess the effectiveness of those devices in drag reduction around the tractor-trailer gap region. Three cases with different drag reduction devices have been studied and significant drag reduction (above 30%) has been achieved for all three cases. Detailed analysis of the flow field has been carried out to understand drag reduction mechanisms, and it shows that no matter what drag reduction devices are deployed the drag reduction is mainly due to the reduced pressure on the front face of the trailer, and a small proportion of the drag reduction is due to the reduced turbulent kinetic energy in the gap region.

The dynamical analysis of MHD second grade fluid based on their physical properties has stronger resistance capabilities, low-frequency responses, lower energy consumption, and higher sensitivities; due to these facts externally applied magnetic field always takes the forms of diamagnetic, ferromagnetic and paramagnetic. The mathematical modeling based on the fractional treatment of governing equation subject to the temperature distribution, concentration, and velocity field is developed within a porous surfaced plate.  Fractional differential operators with and without non-locality have been employed on the developed governing partial differential equations. The mathematical analysis of developed fractionalized governing partial differential equations has been established by means of systematic and powerful techniques of Laplace transform with its inversion. The fractionalized analytical solutions have been traced out separately through Atangana-Baleanu and Caputo-Fabrizio fractional differential operators. Our results suggest that the velocity profile decrease by increasing the value of the Prandtl number. The existence of a Prandtl number may reflect the control of the thickness of momentum and enlargement of thermal conductivity.

We introduce smaller artificial factors into the elastic constants matrix and manage to make Mindlin first-order plate theoryequations of motions coupled for a uniform and integrated analysis. The energy distributions of the five coupled modes are obtained and all the five vibration modes are identified through the energy calculation. This analytical approach based on artificial couplings of vibration modes suggests that all vibration modes of structural components can be analyzed through the same procedure and computer code if the right elastic constants are modified and the mode identification can be done with the energy method. This is a new technique to study multimode vibrations of structures in a broad frequency range with just one procedure and calculation tool for simplification.

A nonlinear oscillator arising in the microelectromechanical system is complex and it is difficult to obtain a variational principle. This paper begins with a wrong variational formulation and uses the semi-inverse method to obtain a genuine variational principle. Additionally, this paper gives simple formula for the fast frequency estimation of the nonlinear oscillator. Only simple calculation is needed to have a relatively high accuracy results when compared with the other methods.

The present paper reports the numerical results of fluid flow in porous phase change materials (PCM) media. This is an important topic in potential scientific, technological and engineering field’s especially latent heat storage. In this paper, we are only interested in the correlation between permeability and porosity of the porous media and not in latent storage. Fluid flow is characterized by many parameters mainly permeability and porosity. Many models have been proposed for the study of this phenomenon over the years. However, it can be modeled using the complex model that studies the characteristics of pore microstructure and fluid flow in porous media. This model is more accurate and realistic compared to previous models. It predicts permeability and porosity with a good agreement with experimental data. In this paper, the complex model is used to determine the impact of the tortuosity and the density of capillary distribution on the relation between permeability and porosity and check their scaling laws with universal exponents independently of other parameters. The results show that the permeability-porosity relation is proportional to the standard deviation of capillary distribution and its density. The tortuosity affects porosity proportionally, and permeability inversely. The relation between porosity and permeability follows a power law with universal exponents β = 4.06 ± 0.12 for different values of the expectation of distribution, the density of capillaries and the tortuosity; and β = 1.69 ± 0.01 for different values of the standard deviation, density of capillaries and tortuosity. The universality of these exponents further validates the complex model with various previous experimental and numerical studies.

Performance of two axisymmetric air intakes are compared at conditions suitable for Mach number range from 2 to 8. First is the Busemann intake and second is the reversed isentropic nozzle. The isentropic nozzle is built by the method of characteristics. The contour of this nozzle is taken as a compression surface for the incoming flow. Performances of these two intakes are compared by comparison of both viscous and inviscid CFD calculations at Mach 6. Viscous flow calculations show that the total pressure recovery in compression section is 0.8316 in the Busemann intake and 0.869 in the reversed isentropic nozzle intake.

A pair of rogue wave solutions of the Davey-Stewartson (DS) equations are obtained by using the exp-function method and reduction transformations. Firstly, the Davey-Stewartson equations are transformed into two easy-to-solve equations, one of which is the deformed nonlinear Schrödinger (NLS) equation and the other is a polynomial equation. Secondly, based on the existing known solutions of the deformed NLS equation constructed by the exp-function method, rogue wave solutions of the DS equations are obtained. Finally, some spatial and spatiotemporal structures and dynamical evolutionary plots of the obtained rogue wave solutions are shown.

This work presents forced vibration responses of a cantilever beam made of functionally graded material under a harmonic load. The material properties of beam vary along the axial direction. The kinematics of the beam are considered within Timoshenko beam theory. The governing equations of problem are derived by using the Lagrange procedure. In the solution of the problem the Ritz method is used and algebraic polynomials are used with the trivial functions for the Ritz method. In the solution of the forced vibration problem, the Newmark average acceleration method is used in the time history. In this study, free and forced vibration responses of the axially functionally graded beam are investigated in detail. In the numerical examples, the effects of material graduation, geometric and dynamic parameters on the free and forced vibration response of axially graded beam are investigated.

We examine the velocity field of an incompressible Oldroyd-B fluid over a horizontal plate of continual length in a permeable medium with magnetohydrodynamics effect. Firstly, the results for the dimensionless classical model (governing equation) have been studied analytically then the study is extended for different fractional operators. The relations to determine the velocity fields of this problem are found by Laplace transformation and different numerical inversion algorithms. The impact of physical parameters on velocity profiles is analyzed graphically for integer and non-integer models. Non-integer operators are used to analyzing the impact of fractional parameters on the fluid curves of the fluid.

In this paper, the Lie symmetries and similarity reduction of a class of wave equations are investigated. First, Lie algorithm is used to get the determining equations of symmetry for the given equations which are complicated and difficult to be solved. Next, differential form of Wu’s method is used to solve this problem. Moreover, a special case of differential invariant method is used to get similarity reduction of the given equations.

The Spectral/HP element method has been applied to perform Direct Numerical Simulations (DNS) over a single T106A turbine blade-row using the open source software Nektar++. The main goal of the current study is to perform preliminary investigations at modest Reynolds and Mach numbers, 8000 and 0.1 respectively, for uniform, steady flow past the aerofoil by employing Nektar++’s solver for the 2D Navier-Stokes equations for incompressible flow. The mesh was firstly validated against results obtained using the same software and for a similar set of parameter values. One dimensional, pitch-wise harmonic vibrations were subsequently imposed on the blade by means of a coordinate transformation. A parametric study in terms of the frequency and amplitude of the vibrations was carried out. The effects of the vibrations on entire domain, along the blade surface and in its wake were assessed. The pressure on the blade surface and the wake loss were each decomposed into components arising due to the mean flow and due to the vibrations. In each case the dominant components were then identified for the values of frequency and amplitude considered here.

Non-ductile reinforced concrete (RC) members are common in the existing RC frame buildings with the old seismic code (lightly and inadequately detailed transverse reinforcement) and may suffer shear failure or flexure-shear failure. To investigate the failure behaviors of those RC structures, performance-based numerical models are needed. Thus, a new fiber frame element on Winkler-based foundation including the interaction effects between shear and flexure was developed to analyze non-ductile RC frames resting on foundation, in this study. The proposed element is formulated for implementation in displacement-based finite element formulation under the kinematic assumptions of Timoshenko beam theory. As a result, axial and flexural mechanisms are automatically coupled through the fiber-section model, while shear and flexural actions interact via the UCSD shear-strength model within the framework of modified Mergos-Kappos interaction procedure to evaluate sectional shear force and shear stiffness within the shear constitutive law. Therefore, the presented model is simple, but able to capture several salient behaviors of non-ductile RC frames resting on foundation, including interaction between shear and flexure, soil-structure interaction, degradation of shear strength due to inelastic flexural deformation, and shear failure. Those features and efficiency of the proposed model are demonstrated by two numerical simulations in this work.

The control problem of the dynamics of actuators is considered to obtain a given optimal movement of the end-effector for a parallel Dexterous Twin Arms Robot (DexTAR). The trajectory is assumed to be known in advance, and the law of motion along the trajectory is given from some optimality conditions. The equations of dynamics of the robot are written under the condition that the leading rods are driven by torques of a symmetrically arranged pair of engines. The solutions of the direct and inverse kinematic problems are presented as auxiliary material. The resulting nonlinear motion equations are derived. A numerical example shows that the equations can be simplified neglecting the change in the angle between the rods at the end-effector. Numerical examples of calculating the torques are given.

In this paper, a fractal modification of the Riccati differential equation is presented, and the two-scale transform method combined with Taylor series is used to solve the equation. Two examples are given to verify the correctness and effectiveness of the proposed method.

On the microgravity condition, gravity affects the motion of objects and the flow of fluids, and the continuum assumption is not valid, therefore, a fractal Chaplygin-He gas model is developed by a new fractal derivative in microgravity space. A fractal variational principle is successfully established via the fractal semi-inverse method.

This article explores the MHD natural convective viscous and incompressible fluid flow along with radiation and chemical reaction. The flow is confined to a moving tilted plate under slanted magnetic field with variable temperature in a porous medium. Non-dimensional parameter along Laplace transformation and inversion algorithm are used to investigate the solution of system of dimensionless governing equations. Fractional differential operators namely, Caputo (C), Caputo-Fabrizio (CF) and Atangana-Baleanu in Caputo sense (ABC) are used to compare graphical behavior of for velocity, temperature and concentration for emerging parameters. On comparison, it is observed that fractional order model is better in explaining the memory effect as compared to classical model. Velocity showing increasing behavior for fractional parameter a whereas there is a decline in temperature, and concentration profiles for a. Fluid velocity goes through a decay due to rise in the values of M, Sc and j. However, velocity shows a reverse profile for augmented inputs of Kp , Gr and S. Tabular comparison is made for velocity and Nusselt number and Sherwood number for fractional models.

The aim of this paper is to analyze the problem of magneto hydrodynamic Jeffrey-Hamel flow (JHF) with nanoparticles. The governing equations for this problem are reduced to an ordinary differential equation and it is solved using new analytical method (NAM) and fourth-order Runge-Kutta Method (RK ∼ 4). The NAM is an iterative method that relies mainly on derivatives with Taylor expansion interference. In addition, the velocity profile has been computed and shown for various values of physical parameters. The objective of the present work is to investigate the effect of the angles between the plates, Reynold number, magnetic number and nanoparticles volume fraction on the velocity profile.

In this paper, we implement the multidomain spectral relaxation method to numerically study high dimensional chaos by considering the nine-dimensional Lorenz system. Chaotic systems are characterized by rapidly changing solutions, as well as sensitivity to small changes in initial data. Most of the existing numerical methods converge slowly for this kind of problems and this results in inaccurate approximations. Spectral methods are known for their high accuracy. However, they become less accurate for problems characterised by chaotic solutions, even with an increase in the number of grid points. As a result, in this work, we adopt the multidomain approach which assumes that the main interval can be decomposed into a finite number of subdomains and the solution obtained in each of the subdomains. This approach remarkably improves the results as well as the efficiency of the method.

Non-uniform grids inevitably arise in multiphase flow simulation scenarios due to the need to resolve near-wall phenomena and/or large L/D ratios associated with the reactor configuration. This in conjunction with large density ratios of the constituent phases can retard the convergence of the pressure-correction equation that results from applying operator-splitting methods to the incompressible Navier-Stokes equations. Various pre-conditioning strategies to this ill-conditioned pressure-correction matrix are explored in this study for a class of bubbling bed simulations encompassing: different particle densities, bed-heights and dimensions (2D/3D). The right-side Block Jacobi preconditioning option resulted in a 20 - 35% decrease in CPU time that correlated well with a decrease in the number of iterations to reach a specified tolerance.

This work presents a multi-fault classification system using artificial neural network (ANN) to distinguish between different faults in rotating machines automatically. Rotation frequency and statistical features, including mean, entropy, and kurtosis were considered in the proposed model. The effectiveness of this model lies in using Synthetic Minority Over-sampling Technique (SMOTE) to overcome the problem of imbalance data classes. Furthermore, the Relief feature selection method was used to find the most influencing features and thus improve the performance of the model. Machinery Fault Database (MAFAULDA) was deployed to evaluate the performance of the prediction models, achieving an accuracy of 97.1% which surpasses other literature that used the same database. Results indicate that handling imbalance classes hold a key role in increasing the overall accuracy and generalizability of multi-layer perceptron (MLP) classifier. Furthermore, results showed that considering only statistical features and rotational speed are good enough to get a model with high classification accuracy.

The problem of optimal control of the reorientation of a spacecraft as a solid body from an arbitrary initial ‎position into a prescribed final angular position is considered and solved. The case is ‎studied in detail when the ‎minimized index combines, in a given proportion, the integral of modulus of angular momentum and duration of ‎maneuver. It is proved that the accepted optimality ‎criterion guarantees the motion of a spacecraft with modulus of ‎angular momentum not exceeding the required value. Formalized equations and expressions for the synthesis of ‎the optimal rotation program are obtained using quaternion models. It is shown that the optimal solution corresponds to the strategy “acceleration - rotation with constant modulus of angular momentum-‎braking”, the ‎angular momentum and the controling moment are perpendicular during optimal rotation between acceleration and ‎braking. On the basis of necessary optimality conditions, the ‎main properties, laws, and key characteristics ‎‎(parameters, constants, integrals of motion) of the ‎optimal solution of the control problem, including the turn time ‎and the maximum angular momentum for the optimal motion, are determined. An estimation of the influence of the ‎bounded ‎controling moment on the character of the optimal motion and on the indicators of quality is ‎made. The ‎construction of an optimal control program of rotation is based on the quaternion variables and Pontryagin’s ‎maximum principle. The value of maximal angular momentum magnitude is calculated by condition of ‎transversality. The designed method is universal and invariant ‎relative to the moments of inertia. For dynamically ‎symmetric spacecraft, a complete solution of ‎the reorientation problem in closed form is presented. An example ‎and results of mathematical ‎modeling of the motion of a spacecraft under optimal control are presented, ‎demonstrating the ‎practical feasibility of the method for controlling spacecraft's spatial orientation.

To learn the dynamic characteristics of a mold oscillator, we establish a model that describes the relationship between force equilibrium of a hydraulic cylinder and mold under various oscillation conditions. The non-linearity caused by the servo-value and the operating fluid is considered as excitation, and is calculated as control error between an input signal and mold oscillation in real-time by a PID control process. Based on the non-linear property, we determine that the dynamic behavior is caused by mold oscillation displacement and hydraulic cylinder pressure. We define excitation frequency and harmonic terms, and determine that the sources of the harmonic peak frequency and high peak frequency; (50n ± exciting frequency ωexc) are friction between the piston and hydraulic cylinder, and variable stiffness of the operating fluid. Finally, a mathematical model of the hydraulic chamber that can represent the unknown non-linear phenomenon is derived.

In this work, a generalized higher-order time-derivatives model with phase-lags has been introduced. This model is applied to study the thermal heat problem of a homogeneous and isotropic long cylinder due to initial stress and heat source. We use the Laplace transform method to solve the problem. The numerical solutions for the field functions are obtained numerically using the numerical Laplace inversion technique. The effect of the higher-order parameters, the initial stress, the magnitude of the heat source and the instant time on the temperature field, the displacement field, and the stress fields have been calculated and displayed graphically and the obtained results are discussed. The results are compared with those obtained previously in the contexts of some other models of thermoelasticity.

Numerical modeling of heat and hydrodynamics processes in the channels of compact small diameter tube bundles with different transverse shifted arrangement is carried out. The fields of velocities, temperatures, and pressures in the tube bundle channels were obtained, and their influence on heat transfer conditions and hydraulic losses were analyzed. The calculation of the thermohydraulic efficiency for different constructions of the tube bundles had been carried out, and their results with data of well-known tube bundles of different geometry are compared.

 In this paper, the fractional Sumudu decomposition method (FSDM) is employed to handle the time-fractional PDEs and system of time-fractional PDEs. The fractional derivative is described in the Caputo sense. The approximate solutions are obtained by using FSDM, which is the coupling method of fractional decomposition method and Sumudu transform. The method, in general, is easy to implement and yields good results. Illustrative examples are included to demonstrate the validity and applicability of the proposed technique.

The thermo-hydraulic performances of the shell-and-tube heat exchangers with different baffles inclination angle α =10°, α =20°, and α = 40° are investigated. The numerical analysis has been evaluated using ANSYS Fluent with the finite volume method for Reynolds number varying between 24000 and 27000. In all heat exchangers, the characteristics studied are the velocity, the temperature in the shell, the heat transfer coefficient, the pressure. The results showed small dead zones for the baffles inclination angle of 40°. The results showed that the temperature increases by 3.4 K, the heat transfer coefficient decreased by 0.983 %, the pressure drop decreased by 0.992 %, the overall performance factor decreased by 0.83 % when the baffles inclination angle α is increased from 10° to 40°.

In this paper, we introduce and study some new classes of multivalent (p -valent) meromorphically starlike functions involving Higher-Order derivatives. For these multivalent classes of functions, we derive several interesting properties including sharp coefficient bounds, neighborhoods, partial sums and inclusion relationships. For validity of our results relevant connections with those in earlier works are also pointed out.

This paper aims to investigate, through the 3D numerical analysis of an idealized arterial bypass graft, the dependence of the resistance to flow on the bypass insertion point. The computational model assumes a laminar steady-state Newtonian fluid flow and three different Reynolds numbers: 150, 250, and 400. In this study, the constructal theory has been employed, a self-standing law in physics which covers the statement of minimum flow resistance to optimize morphing architectures, i.e. the coronary artery bypass grafting. According to the Constructal Design method, the constraints are stenosis degree, junction angle, and diameter ratio, while the attachment point is defined as a design parameter. The results demonstrate that the distance between the bypass attachment point and the stenosis influences the pressure drop; more specifically, the pressure drop decreases with the augmentation of the distance. In this regard, a different distribution of the mass flows between the bypass, and the artery is observed and seemed to be the main reason for that behavior. The application of the Constructal Design method in hemodynamics is a tool to describe the biological system to search for better flow performance since it is based on the natural evolution of living systems.

In this study, the buckling problem of shells consisting of functionally graded ‎materials (FGMs) under uniform compressive lateral pressure is solved at mixed ‎boundary conditions. After creating the FGM models, the basic differential equations ‎of FGM shells under compressive lateral pressure are derived within the scope of ‎classical shell theory (CST). The basic differential equations are solved with the help ‎of Galerkin method and the formula for the lateral buckling pressure is obtained. The ‎minimum values of the lateral buckling pressure are found numerically by minimizing ‎the obtained expression according to the numbers of transverse and longitudinal ‎waves. The accuracy is confirmed by comparing the numerical values for the lateral ‎buckling pressure of homogeneous and FGM shells with the results in the literature. ‎The influences of FGM profiles and shell characteristics on the magnitudes of lateral ‎buckling pressure are investigated in detail by performing specific numerical analyzes.

A new method is described, allowing to locate and also measure the length and orientation of crack-type damage features in thin-walled composite beams (TWCB), a capability not previously reported. The method is based on a modal-analysis technique and is shown to work on a hollow composite beam, going beyond previous work limited to simple beams and plates. The method is shown to be capable to function down to signal-to-noise ratios (SNR) of about 15, corresponding to far noisier conditions than in most previous work. This capability is achieved by a combination of wavelet de-noising and the use of a 2D Continuous Wavelet Transform (CWT), applied to two modal analysis metrics, COMAC and Mode Shape Differences (MSD). The length and orientation of the crack can be determined accurately using a 2D curve fitting approach. Using either COMAC or MSD produces reliable results, but MSD is found to be somewhat more noise-tolerant. The new method is believed to be useful for the measurement of damage features in a variety of thin-walled composite beams such as aircraft wings and wind turbine blades, among others.

This paper demonstrates a case study of a combined application of smart materials in a thermal energy harvester with vibrating action. The conceptual design of the harvester is based on a Shape Memory Alloy wire attached to the free end of a piezoelectric flexible cantilever beam intended for generation of electrical energy utilizing a constant heat source. A mathematical model containing three differential equations describing the dynamics of the mechanical, electrical and thermal subsystems is developed. The Shape Memory Alloy hysteretic behaviour is considered in the mathematical model. An essential observation is the system oscillates at two frequencies lower one of which depends on the temperature time constant and the higher one is determined by the natural frequency of the mechanical subsystem. The comparison of the numerical solutions and the experimentally obtained graphs of the harvester output characteristics shows a good degree of coincidence.