https://jcme.iut.ac.ir/ Journal of Computational Methods in Engineering en daily 1 Fri, 22 May 2026 00:00:00 +0330 Fri, 22 May 2026 00:00:00 +0330 https://jcme.iut.ac.ir/article_3766.html In this study, a rectangular component with internal heat generation is considered, which incorporates parallel cooling channels. Some of these channels are active (containing flowing coolant fluid), while others are passive (containing stagnant fluid). The active and passive channels are interconnected through micro thermal switches. When heat flux increases in a specific region of the component, the passive channels in that region convert to active channels, thereby enhancing cooling in high heat-flux areas and reducing the components’ temperature. The fluid flow in this research is assumed to be steady and turbulent. Results demonstrate that cooling is more effective near the channel inlets where thermal switches activate, with cooling performance improving as heat flux increases. The maximum observed temperature difference in turbulent flow was 56°C, occurring when thermal switches opened the pathway between active and passive channels at 200 mm from the inlet of the second channel. The proposed novel self-regulating passive cooling system was evaluated, with calculations confirming optimal heat transfer and cooling performance in this configuration. The positioning of thermal switches relative to the maximum heat flux application zone significantly impacts cooling effectiveness. When switches open before the peak heat flux region, maximum component temperature is substantially reduced. Additionally, components with lower thermal conductivity exhibit greater reductions in peak temperature when utilizing this new passive cooling system. https://jcme.iut.ac.ir/article_3758.html In this research, a novel size-dependent meshfree method is proposed within the framework of the nonlocal strain-gradient theory in order to evaluate the buckling behavior of functionally graded metal–semiconductor nanoplates reinforced with graphene nanoplatelets. The nanoplates with elastically restrained edges are rested on a Winkler–Pasternak elastic foundation. The presented model simultaneously accounts for the effects of nonlocal stiffness and strain gradient, thereby covering the intrinsic softening and stiffening mechanisms at the nanoscale. The governing equations are derived using the principle of minimum total potential energy, and are discretized using the moving Kriging meshfree method. This method effectively resolves the higher-order derivatives appearing in the nonlocal strain-gradient theory. The mechanical properties corresponding to each layer of the plate through the thickness, reinforced by graphene nanoplatelets, are determined using the modified Halpin–Tsai micromechanical model together with the rule of mixtures. Comparison of the results obtained from the proposed method with available analytical and numerical approaches confirms the accuracy and computational efficiency of the proposed method. Furthermore, a parameter-based investigation is carried out to clarify the effects of material gradation, graphene weight fraction, nonlocal and strain-gradient parameters, circular cutout size, the stiffness of the elastic foundation and stiffnesses of the elastically restrained edges on the buckling responses of the functionally graded graphene-reinforced nanoplates. https://jcme.iut.ac.ir/article_3767.html Nowadays, due to high quality and efficiency of dental implants, implantation is considered as the best method for replacing the missing teeth. However, some challenges such as the stress-shielding phenomenon can affect the successfulness of this approach. In this research, the effect of a bidirectional functionally graded titanium-hydroxyapatite structure on the mechanical properties and fatigue life of a dental implant screw, by providing a suitable function for changing the mechanical properties from titanium to hydroxyapatite in the implant screw, was investigated using the finite element simulation. The aim of this study is to compare the performance of the bidirectional functionally graded implant screw with unidirectional functionally graded and titanium implant screws, to reduce the stress-shielding phenomenon and evaluate its fatigue life. Some simplifying assumptions such as isotropic linear elastic behavior for the jawbone were employed. The implant screw and the abutment were modeled as an integrated unit. A rigid ceramic crown with simplified geometry was modeled tied to the abutment. For modeling the jawbone geometry, the section of the lower jaw in the molar teeth area was adopted. The influence of adjacent teeth was ignored, and a single tooth was modeled within the jawbone. The results indicate that the bidirectional functionally graded structure for the screw may reduce the stress-shielding effect. Moreover, compared to the unidirectional functionally graded case, the displacements experienced by the jawbone decrease and hence, prevent damaging the adjacent teeth and jawbone. It is worth mentioning that the proposed bidirectional functionally graded screw satisfy the infinite fatigue life condition, as it should be. https://jcme.iut.ac.ir/article_3768.html This study proposes a practical method for planning multi-stage explosive demolition of multi-story steel structures using nonlinear dynamic analysis and energy-based performance measures in SAP2000. A ten-story steel moment-resisting frame with composite floors is modelled by considering inelastic behaviour through concentrated plastic hinges, second-order effects, and direct time integration with viscous damping. Critical columns at one of the intermediate stories and at the ground story are divided into three blasting groups at each level and removed sequentially with a fixed short interval. At the same time, the delay between the two story-level sequences is treated as the main demolishing variable and examined across multiple scenarios. Performance is assessed using three dimensionless indicators representing collapse efficiency, kinetic response severity with residual motion, and energy-balance consistency. A hierarchical selection rule is applied first, excluding scenarios that fail the energy-consistency requirement and then, ranking the remaining cases primarily by collapse efficiency and secondly by the kinetic indicator. Results show that an intermediate inter-story delay produces a decisive gravity-driven collapse with strong but controlled motion, while very small or very large delays tend to cause incomplete collapse or persistent oscillations. Additional analyses on eight- and five-story steel structures indicate that the proposed assessment logic remains robust with changes in structural height and can support engineers in selecting effective blasting schedules. https://jcme.iut.ac.ir/article_3770.html Turbulence models serve as essential tools for analyzing and simulating the behavior of turbulent flows in tubular thermal economizers. This study presents a comprehensive and in‑depth assessment of several turbulence models, each characterized by its specific capabilities and applications. These models facilitate an improved understanding of heat transfer mechanisms and flow behavior under varying operating conditions. For the economizer of the Isfahan thermal power plant with a capacity of 120 MW, the evaluated results indicate that the actual heat transfer coefficient of the outlet water is 98.68 W/m²·K, while that of the outlet flue gas is 78.16 W/m²·K. The simulations and analyses were conducted using ANSYS Fluent. According to the obtained results, the LES model was identified as the most accurate approach, achieving a turbulence prediction accuracy of 99.39%. Furthermore, the LES model estimated the outlet water heat transfer coefficient as 80.68 W/m²·K and the outlet gas heat transfer coefficient as 67.16 W/m²·K, values that closely match the actual measurements from the Isfahan power plant. These findings not only demonstrate the superior performance of the LES model but also highlight its potential for application in the design optimization and performance enhancement of thermal economizers. https://jcme.iut.ac.ir/article_3771.html This paper presents a novel approach to improve the accuracy and stability of the finite point method (FPM) in the vicinity of points with weak singularities by incorporating equilibrated singular basis functions (EqSBFs). Singular points play a crucial role in the intensification of the flux field in applied physics. Conventional numerical methods fail to correctly capture the solution function in singular areas due to the usage of smooth basis functions. FPM is a meshfree method based on strong point-wise application of the governing partial differential equation (PDE) along with the boundary conditions, which in its classical form suffers from inconsistency of its polynomial type basis functions with the singular region, leading to accuracy reduction, slow convergence, and local instabilities. To address this issue, EqSBFs are incorporated alongside the conventional smooth basis functions. EqSBFs are derived by the weighted residual imposition of the homogeneous PDE, with the capability of automatically identifying the singularity order of the problem, thus avoiding the solution of a parallel identical problem to extract the required singular terms. EqSBFs may be simply merged with the smooth basis functions of the FPM through the weighted least squares (WLS) approximation. The proposed formulation significantly improves the numerical representation of the singular solution, while maintaining the desirable advantages of the FPM. https://jcme.iut.ac.ir/article_3772.html Multiscale modeling of microstructural evolution in polycrystalline metals is commonly conducted based on the concept of a representative volume element (RVE), which characterizes the response of a material point. In this study, a coupled phase field and dislocation density-based crystal plasticity framework is used to investigate the effect of RVE size on the kinetics of static strain-induced grain boundary migration. The finite element-based crystal plasticity model is employed to compute the stored deformation energy distribution within individual grains, while the phase field model describes the subsequent grain boundary migration during high-temperature annealing. The simulations of grain growth are performed for a polycrystalline aluminum with elastic cubic symmetry under plastic uniaxial loading. The RVE size is varied in the range from 10 to 60µm for simulations of static strain-induced grain boundary migration. The initial average grain diameter for all RVEs is 3 µm. The periodic boundary condition is applied to statistical RVEs with sufficient scale separation between the microstructure and macrostructure. To determine the optimum RVE size under a specific boundary condition, a convergence analysis is performed by plotting the grain growth component as a function of RVE size. The simulation results indicate that an RVE size of 30 µm statistically provides a representative response for tensile loading conditions. The outcomes of this work provide valuable insights for determining the optimum RVE size and for the design of thermomechanical processing strategies in metallic materials. https://jcme.iut.ac.ir/article_3773.html This study presents a thermodynamic and environmental analysis of four configurations of E-class and F-class gas turbines and their corresponding combined cycles (CCGT-E and CCGT-F) to explain some of the advantages of combined cycles over gas turbine cycles. Energy and exergy analyses were conducted to evaluate efficiency, exergy destruction, specific CO2 emissions (SCE), and sustainability indices. A novel environmental exergy sustainability index (EESI) was developed and its mathematical proof was presented. The results demonstrate that CCGT-F achieves the highest exergetic sustainability index (ESI) and EESI values of 1.13 and 1.72, respectively. CCGT-F, with a thermal efficiency of 56.31% (17.04% higher than GT-F), and CCGT-E, with an efficiency of 48.73% (14.67% higher than GT-E), exhibit superior performance. From an environmental perspective, CCGT-E and CCGT-F reduce CO2 emissions by 30.1% and 39.5% compared to GT-E, respectively. Conversion of the country's gas power plants to combined cycle could add at least 7,000 MW grid generation capacity, save fuel, and prevent at least 50,000 tons of daily CO2 emissions. https://jcme.iut.ac.ir/article_3774.html Abstract: Rolling contact fatigue is one of the most common failure mechanisms in bearings, manifesting as surface and subsurface cracks that ultimately lead to pitting. This failure, resulting from repeated stresses in the contact region between the rolling element and the raceway, can severely affect system performance, making its accurate prediction essential from a design and durability perspective. In this study, in order to achieve a more accurate estimation of fatigue life associated with pitting, the actual contact friction coefficient is first determined based on reliable experimental data, and then the Hertzian surface and subsurface stresses are calculated. The analyses indicate that the maximum subsurface shear stress plays a decisive role in the initiation of cracks associated with pitting. Subsequently, three fatigue models‚ the continuum damage mechanics model, the Ioannides–Harris empirical model, and the Zaretsky statistical model are implemented and compared. The results show that the continuum damage mechanics model provides higher accuracy under high load conditions, the Zaretsky model yields predictions close to experimental data, and the Ioannides–Harris model exhibits more conservative behavior in certain stress ranges due to the presence of a fatigue limit. The discrepancies among these predictions highlight the importance of selecting an appropriate fatigue model and the role of the fatigue threshold in life assessment. The findings of this research, by offering a simple yet accurate framework, can be applied to the design and performance improvement of industrial bearings. https://jcme.iut.ac.ir/article_3775.html The performance of a propeller, specifically its thrust and torque, critically affects the overall efficiency of propeller-driven vehicles. This study numerically investigates a flying boat propeller with a diameter of 2 m, operating at a rotational speed of 2200 rpm and an advance speed of 180 km/h. The three‑dimensional, compressible, turbulent airflow is modeled using the SST k‑ω turbulence scheme, and blade rotation is accounted for via the moving reference frame (MRF) approach. The effects of rotational speed, blade pitch angle, and vehicle advance speed on thrust and torque are quantitatively evaluated. ANSYS Fluent commercial code was utilized for performing numerical simulations. The CFD results showed a reasonable agreement with experimental results. Key results show that increasing the rotational speed from 2000 rpm to 2200 rpm raises the thrust by approximately 180\% and the torque by 67\%. A 2‑degree increase in the blade pitch angle yields respective increases of 61\%, 42\%, and 14\% in thrust, torque, and efficiency. In contrast, the advance speed has an inverse effect: at 210 km/h, thrust, torque, and efficiency drop to only 5\%, 43\%, and 13\% of their values at 150 km/h, respectively. These findings demonstrate the strong sensitivity of the propeller performance to the operational parameters, especially advance speed, and provide quantitative benchmarks for design applications in compressible flow regimes.