Journal of Computational Applied Mechanics
Volume:53 Issue: 2, Jun 2022

Selective catalytic reduction (SCR) is an emission control method that reduces the NOx emission using urea sprays as ammonia precursors for exhaust after-treatment systems. The urea injection system is an essential component of the SCR systems. A comprehensive SCR modeling approach is required to design compact after-treatment systems that meet the NOx emission legislation level. In this study, the characteristics of urea spray injectors of the SCR system were investigated using computational fluid dynamics (CFD) and the particulate image velocity (PIV) technique. A validation strategy was developed to model the urea spray evaporation, liquid/wall contact, and formation of solid urea deposits. The sheet atomization model was modified to improve the performance of the CFD model. While the Rosin-rammler method predicted the results of 10% according to the experimental results, the proposed tabular method decreased the difference by 3%. In addition, 500 parcels were determined as an optimum number of parcels for urea spray according to the sensitivity study. Therefore, the validation methodology was proposed to predict more consistent results for urea spray modeling and the formation of solid urea deposits.

This research employs a hierarchical fuzzy control method to guide and control autonomous robots in environments containing fixed and moving obstacles. Considering that robots must operate in social environments to serve humans better, they must be able to navigate in the presence of fixed obstacles, moving objects and people without colliding or creating a fear of collision, and reach the final destination. The current work utilizes a hierarchical fuzzy controller with three agents of navigation, obstacle avoidance, and perception to achieve these goals. The coordination between these three agents is done using the definition of special utility functions. The obtained results confirm the correctness of the proposed approach in the successful passage of the robot past the fixed and moving obstacles and bringing it to the target point.

Ankle sprain is one of the most prevalent joint injury in the lower extremity. Valid and reliable measurement techniques is essential for the collection of accurate and meaningful data about joint injuries such as ankle sprain. We design this case-control study to evaluate the test–retest reliability of force plate measures and compare the static postural control values in in patients with chronic ankle Instability (CAI), ankle sprain copers & healthy controls. Seventy five patients (25 CAI, 25 copers & 25 healthy match controls) were asked to execute single-leg stance onto a force plate. Force plate parameters include, the COP area, COP length, mean total velocity and sway index were measured for static postural control evaluation. To evaluate test–retest reliability, 20 participants of each group repeated the tests 6–8 days after the first session. Relative reliability of the force plate measures was assessed using interclass correlation coefficient (ICC) and absolute reliability using standard error of measurement (SEM), minimal metrically detectable change (MMDC) and coefficient of variance percent (CV%). Analysis of variance (ANOVA) was used to determine differences between three groups. Static postural control measures have high test–retest reliability, ranging from 0.73 to 0.88. Greater postural sway has been observed in the CAI compared with the coper (P< 0.05) and the matched limb of the control group (P<0.05). Static postural control measures are reliable tests to evaluate functional performance of the patients with CAI, copers and healthy controls.

The current investigation aims to peruse the discrepancies between the endurable transverse buckling load of multi-layer fibrous composite and fiber-metal laminate (FML) I-section beams. Using the energy method, the governing differential equations are extracted in accordance with the classical laminated plate theory and Vlasov’s model for non-uniform torsion. Then, the equilibrium equations system is numerically solved via the differential quadrature method as a powerful and accurate technique, and finally, the lateral buckling load is calculated. Numerical results are presented for a simply supported I-beam under gradient moment. The accuracy of the proposed method is examined by comparing the results with those obtained by ANSYS finite element software. By considering the best conventional stacking sequences, the lateral stability strength of FML and laminated composite beams with I-shaped cross-sections are compared to each other for different fiber composite materials, end moment ratios, mode numbers, and metal volume fractions of the web and both flanges. The results show that the transverse buckling load of the selected I-beam is significantly affected by the mentioned parameters. In addition, the numerical outcomes indicate that the lateral buckling capacity of CARALL is more than GLARE for all analyzed cases.

This work is centered on propagation, reflection and transmission of waves in a micropolar fibre reinforced thermo-elastic solid and inviscid liquid interface in the presence of magnetic fields. Green and Lindsay thermo-elastic theory is utilized for non-insulated boundary of the solid media. P-wave incident at joint surface of the micropolar fibre reinforced thermo-elastic solid-liquid media in the presence of magnetic field produces four coupled reflected waves; quasi-longitudinal displacement (qLD), quasi-transverse displacement (qTD), quasi-transverse microrotational (qTM) and quasi-thermal (qT) wave, and two waves transmitted through the inviscid liquid medium; quasi-Longitudinal transmitted (qLT) and quasi-thermal transmitted (qTT) waves. Harmonic solution method is employed in conjunction with Snell’s laws cum Maxwell’s equation governing electromagnetic fields in the formulations and determination of solution to the micropolar fibre-reinforced solid/liquid modeled problem. Reflection and Transmission coefficients which correspond to reflected waves are presented analytically and graphically via numerical computations for a particular chosen material using Mathematica Software. Magnetic and thermal relaxation times field parameters have varied degree of effects to the propagation, reflection and transmission of waves in the media as observed. The study would be helpful in understanding the behavior of propagation, reflection and transmission of waves in micropolar fibre-reinforecd magneto- thermo-elastic-acoustic machination fields in solid/liquid interface and future works on the behavior of seismic waves, resulting in fluid interaction especially in geotechnical, physics, amongst others.

In this paper, nonlinear dynamic analysis of sandwich plate with viscoelastic and flexible core and shape memory alloy embedded composite face sheets is performed. In order to simulate the dynamic behavior of sandwich plate, a higher order global-local theory based on the superposition principle is used. One of the most important advantage of presented theory is considering the thickness variation and transverse shear stresses, which is especially necessary in the study of thick sandwiches with soft core. In order to simulate the behavior of the shape memory alloy (SMA) wires, material properties variation are considered continuously in whole of the plate. In order to accurately investigate the behavior of the shape memory alloy, a written code is using an algorithm for solving the dynamic phase transformation base on modified Brinson model. The kinematic equations of phase transformation of embedded SMA wires are coupled with the equations of motion that leads to the nonlinearity and complexity of the equations. So to solve the equations, a development iterative method based on the formulation of nonlinear transient finite elements method with a dynamic phase transformation algorithm is used. The results show that the vibration amplitude of the sandwich plate is reduced due to energy dissipation because of the phase transformation of the SMA wires. Also, the core of the sandwich plate is considered of viscoelastic material. Due to the specific properties of the viscoelastic materials, the dynamic behavior of the structure and its consequence, the overall damping of the structure is affected. One of the previously unexplored studies is the simultaneous investigation of the damping effect of viscoelastic cores and embedded SMA wires. In other words, in this case, the sandwich plate has two different damping mechanisms with different function and nature that affect each other.

Integrating a PEM fuel cell with an improved Kalina cycle to gain more electrical power is presented in this study. The Kalina cycle consists of two turbines and two separators. The waste heat of the PEM fuel cell is the major energy source for the Kalina cycle and industrial waste heat is supplied to the cycle to generate more electrical energy. Thermodynamic and exergoeconomic analysis is carried out on the system components to evaluate the system performance. The results indicate that the proposed system can produce 14.51 % more power in comparison with the standalone PEM fuel cell, while the total cost rates of the system increase by 19.3 %. Moreover, the energy and exergy efficiencies of the proposed hybrid system is 5.01% and 14 % higher than the energy and exergy efficiencies of the standalone PEM fuel cell. The exergoeconomic analysis shows that the fuel cell, the turbines, the compressor and the condenser have the highest cost rates compared to other components of the system. Furthermore, a parametric study is performed on the system to investigate the effect of variations of some key parameters, including PEM fuel cell operating temperature and pressure, current density, ammonia mass fraction and maximum pressure of the Kalina cycle on system performance.

The aim of this work is to investigate a generalized dual phase-lag model with variable thermal material parameters and memory dependent derivatives (VMDPL). In view of this model, the thermoelastic behavior on a half-space under an external body force and subjected to exponentially varying heat is analytically investigated. The governing differential equations are numerically solved using the Laplace transform approach. The effects of the variable thermal material properties and memory dependent derivative on all the physical quantities of a half-space are discussed. The obtained results demonstrate that the physical fields of a half-space depend not only on the distance, but also on the memory time delay and the variable thermal parameter. Furthermore, the variable thermal parameter and the variable thermal parameter has a clear effect on the temperature and the stress but has a negligible effect on the displacement. Finally, the validity of results is acceptable by comparing the displacement, stress and temperature according to the present generalized model (VMDPL) with those due to other thermoelasticity theories

The paper considers the simulation of the mixing of two flows with different velocities in a flat channel. The calculations are based on the numerical solution of a system of non-stationary equations using a two-fluid turbulence model. The results of longitudinal velocity and turbulent stress profiles in different sections of the channel are obtained. For the numerical implementation of the equations of turbulent hydrodynamics, the control volume method was used, and the relationship between velocities and pressure was found using the SIMPLE procedure. In this case, the convective terms in the equations were approximated by the difference against the flow of the second order of accuracy in an explicit way, and the diffusion terms were approximated by the central difference in an implicit form. To confirm the correctness of the obtained numerical results, a comparison was made with experimental data from the NASA database.

Functionally graded porous materials are porous structures with porosity gradient distributed over volume. The porous structures having valuable properties, such as lightweight and excellent energy absorption, have been considerably used in different engineering implementations such as aerospace, biomedical, and other industries. Two limit cases are usually considered for the porous structures: 1- The fluid pressure of pores is zero and 2- The pores fill by incompressible fluid and is in saturated condition. Many investigations have been reported on the behavior of functionally graded porous structures. But, most of them are concerned on the drained conditions. However, the investigations into saturated porous structures are limited in number. The present paper (a) specially reviews the mechanical properties of functionally graded saturated porous structures; (b) presents a comprehensive review on the mechanical analyses of these structures in saturated condition; (c) discusses the challenges and possible future works.