مجله مهندسی مکانیک
پیاپی 139 (مهر و آبان 1400)

One of the most common cardiovascular deseases is stenotic arteries. In this study, blood flow with different models of viscosity in a stenotic artery with the assumption of a wall has been investigated. Stenosis geometry is modeled by cosine relation. for The problem equations including continuity, momentum, energy, Hooke's law for linear elastic material, and the method (ALE) for fluid-solid interaction are defined and solved as finite element code. The results showed that the vessel wall had the most displacement near the stenosis region. Assuming the fluid-solid interaction reduces the wall shear stres. For example, the maximum wall shear stress in the stenotic region decreases from 2.32 to 2.23 with Carreau viscosity and from 2.1 to 2 with Newtonian viscosity. It was also observed that applying heat flux on the outer surface of the vessel wall causes a significant increase in blood flow and the wall temperature in the stenotic region.

A fire accident of a passenger train from Tehran to Ahvaz has been numerically simulated. In this study, emission patterns, temperature distribution and the other parameters have been investigated after the start of the fire. The transient governing equations have been solved by Pyrosim software for different scenario based on mass fraction of products, unused fuel and other fire parameters. The results are compared with an actual case. The results showed that less than two minutes after the start of the fire, the conditions inside the wagon reached a critical situation in terms of temperature, smoke and visibility. To prevent the fire from spreading to other parts of the wagon, firefighting operations must be performed in less than four minutes.

Buckling is one of the main causes of breakdown in thin wall structures, so the possibility of buckling should always be considered in design and analysis. In this research, instability of a rotating drum in a turbine engine with several rows of blades attached to its external environment is analyzed. The rotary drum structure is a thin-walled conical structure that is subjected to a variety of mechanical and thermal loads. The rotary drum is modeled as a conical structure and analyzed in the Abaqus finite element software and verified by theoretical relations. The stresses applied to the structure are determined, and the buckling coefficients, or eigenvalues, are extracted, and the stability of the drum structure and its associated factors are discussed. The results of the analysis show that the effect of thermal loading on the buckling of the drum structure is greater than external pressure loadings. In the cone drum the critical stress is 710 MPa and the maximum working stress is 660 MPa.

Microchannel is a small and efficient heat exchanger which, by combining some features such as high heat transfer coefficient, low fluid volume required and small weight and dimensions, is a very efficient tool in the field of heat transfer purposes. In this article, the slip velocity and temperature jump on the internal flow of the microchannel are investigated. The results show that in each Reynolds number, the slip velocity increases the velocity near the wall, while decreasing the maximum velocity in the center line. The velocity distribution in the microchannel (slip velocity) becomes wider compared to the quantum flow. The velocity in the center line (maximum velocity) decreases with each Reynolds number as the sliding velocity increases. The maximum velocity during the developed flow decreases by about 25% as the Knudsen number increases to 0.1, but this effect is greater on higher Reynolds numbers. In Knudsen numbers and different temperature jumps, increasing slip velocity and temperature jump has a decreasing effect on the temperature at each section. Curved microchannel acts as a direct microchannel. Increasing the nanofluid volume fraction Increases the local Knudsen number at slip-flow and non-slipflow regime.

This research has been carried out with the aim of thermodynamic optimization of Bushehr nuclear power plant with the approach of exergy analysis for the connection of desalination plant and the production of freshwater at the lowest possible cost. After exergy analysis and determination of destruction, gray wolf optimizer and particle swarm algorithms have been used to optimize the system. The performance of these algorithms in solving the Rastrigin function has been evaluated and the main problem has been solved with the superior algorithm to find the optimal temperatures and pressures. Then, a multi-stage distillation desalination unit with a Thermo vapor compressor with a capacity of 24,000 cubic meters per day has been connected to one of the outlet flows of the low-pressure turbine. The results showed that the highest rate of irreversibility and loss with 1510.50 MW belongs first to the reactor and then to 144.50 MW to the steam generator. The cost of producing fresh water in optimal conditions of the power plant is estimated at $ 1.18 per cubic meter.

In the present study, the effect of adding carbon nanotubes on the tensile and flexural behavior of basalt fiber reinforced epoxy composites was investigated. In the first step, in order to better interact the nanotubes with the epoxy surface, their surface modification was performed. Surface-modified carbon nanotubes were applied at different weight percentages relative to the matrix (0.1%, 0.3%, and 0.5%) and then the resulting mixtures were used as a matrix in the fabrication of basalt fiber-reinforced composites. In order to investigate the effect of adding carbon nanotubes on the mechanical behavior of composites, three-point tensile and flexural tests were performed on them. The results show that, firstly, the highest effectiveness of surface-modified carbon nanotubes on tensile and flexural strength is obtained in composites containing 0.3% by weight. Secondly, the positive effect of carbon nanotubes in a certain amount on flexural strength is greater than the effect of the same amount on the improvement of tensile strength. Energy was obtained in a sample containing 0.3% by weight.

The prefix "meta" in "metamaterial" is the Greek word, which means beyond the material. Therefore, metamaterials have properties beyond natural materials. The properties of these materials are not affected by the material from which they are composed, however, their properties depend on their structure. This particular structure in metamaterials is produced by the repetition of similar components or arrays called cells. Therefore, metamaterials have a very complex structure. As a result, the high ability of additive manufacturing to fabricate complex structures has drawn attention to this technology. There are different types of metamaterials that are generally divided into four groups, each of which is widely used in various fields, including defense, automotive, aerospace, and medicine. The purpose of compiling this article is to get acquainted with the types of metamaterials, different cells, applications, and methods of manufacturing these materials comprehensively and categorized. This article also specifically examines the application of metamaterials in the automotive industry.

The noise, which originates from vibration, is significant because it directly affects the quality of human life. One of the essential sources of car noise is tire noise, which becomes prominent by reducing engine and exhaust noises and electrifying cars, and part of it is initiated from the resonance of the tire cavity. In this article, the resonance of the tire cavity was studied, and the primary purpose is to determine the parameters affecting the resonance of the tire cavity and its control solutions of the source of noise and transmission path into the car cabin. Notably, the two problems addressed have not been investigated simultaneously in previous studies. In the present work, for the first time, the tire cavity resonance control solutions are examined and the resonance transmission path into the car cabin. Furthermore, the pros and cons of such an examination were classified as well. The research method is descriptive in which after collecting, studying, and analyzing articles and published researches in the field of tire cavity noise, the concepts, principles, processes, and achievements of each research have been categorized and analyzed. These studies are necessary to investigate and control the effect of tire acoustic cavity resonance on the acoustic environment inside the car cabin.