Articles in This Issue
Abstract
Submarine pipelines are essentially used for the transmission of gas and oil across oceans between countries or for transport between shore and offshore installations. The pipeline applications were studied to be installed in deep water, which exposed to different loads such as currents and waves in various directions, barge movements, seafloor interaction, etc. This paper developed a dynamic analysis of the J-lay suspended submarine pipeline during laying, taking into account the effect of water depth, the direction of the wave heading, and sea state without vessel movement. The finite element program ANSYS R17.2 is used for modeling and analysis of the pipelines. The random sea state is modeled using the JONSWAP spectrum. It was found that the effect of the direction of wave heading on the bending moment from dynamic analysis of pipeline is obvious in a depth of (2 m) below water surface, and then gradually decreases until it disappears in depth of (100 m). Whereas the effect of wave height is obvious in a depth of (2 m) and then gradually decreases until it disappears in depth of (120 m).
Abstract
Constructed wetlands are engineered systems used for wastewater treatment with the objective of reusing water under controlled conditions by mimicking natural treatment mechanisms involving porous media, plants, and microbial communities. This study investigates the performance of a horizontal subsurface flow constructed wetland, where wastewater flows through a gravel bed and vegetation roots, allowing contact with biofilm developed within the wetland substrate. To evaluate treated water quality, physical, chemical, and biological parameters were measured. Field results demonstrated that pollutant removal efficiency increased with detention time. After 3, 4, and 6 days of treatment, average removal efficiencies were 47.7%, 53.2%, and 77.5% for COD; 45.1%, 52.8%, and 64.4% for total nitrogen (TN); and 55.4%, 58.8%, and 72.2% for ammonium (NH₄), respectively. Nitrate removal averaged 19.41% after 3 days. These findings confirm that the horizontal flow constructed wetland system is effective in reducing key wastewater pollutants.
Abstract
Scour around bridge foundations is one of the major causes of severe damage to bridge structures. This study experimentally investigated the effects of key parameters, including pier shape, foundation shape, foundation level, flow intensity, and Froude number, on local scour for non-uniform pier geometries. Three foundation shapes (rectangular, oblong, and hexagonal) and three pier shapes (rectangular, oblong, and hexagonal) were examined, with a constant foundation depth of 8 cm. The results demonstrated that scour depth is strongly influenced by foundation level and by the shapes of both piers and foundations. Among the tested configurations, the hexagonal foundation exhibited the lowest scour depth, followed by oblong and rectangular shapes, respectively. Positioning the foundation below the bed level further reduced scour depth around the pier. Additionally, the hexagonal pier produced the minimum scour because of its smaller exposed surface area. These findings highlight the importance of structural geometry and foundation placement in minimizing local scour at bridge piers.
Abstract
Continuously Variable Transmission (CVT) combines the efficiency of manual transmissions with the driving comfort of automatic transmissions while providing an infinite range of gear ratios, improved fuel economy, and enhanced acceleration performance. This study presents a comparative evaluation of CVT performance against manual and automatic transmissions in a parallel hybrid electric vehicle (HEV), focusing on fuel consumption and exhaust emissions. A baseline HEV model equipped with a CVT gearbox was selected from ADVISOR simulation software and subsequently modified by replacing the CVT with manual and automatic transmissions for comparison. Exhaust emissions, including catalytic converter pollutant reactions, were recorded for all configurations. Performance assessments were conducted using several global standard driving cycles to simulate real driving conditions. Results indicated that the CVT configuration achieved superior fuel economy and a significant reduction in exhaust emissions compared with manual and automatic transmissions. This improvement is attributed to the CVT’s effective control of speed ratio and overall transmission efficiency. The findings support the suitability of CVT gearboxes for urban hybrid vehicle applications due to their low fuel consumption and high efficiency in speed ratio control.
Abstract
This study presents both experimental and theoretical investigations of an absorption refrigeration system using environmentally friendly working fluids, specifically the acetone–zinc bromide (Acetone/ZnBr₂) pair. The system was designed to operate under outdoor climatic conditions in Hilla City, Iraq, utilizing hot water as the heat source. Performance evaluation was carried out under various operating conditions, including changes in heat source, absorber, condenser, and evaporator temperatures. Experimental testing was conducted during September 2019. The results indicated that the coefficient of performance (COP) of the absorption cooling system ranged from 0.13 to 0.487, with an evaporator temperature drop of approximately 16 °C. Condensation and absorption temperatures remained below 41 °C, while the maximum driving water temperature reached 80 °C. A steady-state theoretical model was developed using the Engineering Equation Solver (EES) program, applying mass and energy balance equations to predict operating parameters such as temperature, pressure, and COP. Model predictions showed good agreement with the experimental measurements. Furthermore, the results confirmed that generator temperature has a significant influence on overall system performance.
Abstract
This study focuses on the design and construction of an automated device for evaluating the scratch resistance of polymeric materials by measuring the force required to produce surface scratches and calculating the corresponding friction coefficient from device input–output data. The device was fabricated using locally available materials, with several components manufactured in local mechanical workshops. It comprises four main subsystems: mechanical components, scratching mechanism, electrical and electronic units, and an operating control program. The developed device offers the following specifications: normal load range of 0.1–325 N, sliding speed of 1–35 mm/s, tangential force measurement capacity of 0.1–294 N via a load cell, sample dimensions of 10–195 mm in length, 10–125 mm in width, and 0.25–50 mm in thickness, a maximum scratch length of 195 mm, and an adjustable indenter height ranging from 0.25 to 50 mm above the platform surface. Scratch testing and friction coefficient measurements were conducted on pure PMMA and PMMA reinforced with silicon dioxide (SiO₂) nanoparticles. Experimental results demonstrated increased scratch resistance and reduced friction coefficients with higher SiO₂ weight ratios. Additionally, the performance evaluation confirmed that the designed device is capable of accurately and rapidly measuring the tangential forces associated with scratching through a simple operational procedure.
Abstract
This study presents three-dimensional numerical simulations of single-phase laminar flow and forced convection heat transfer of water in a five-layer microchannel heat sink with two channel configurations: radial arrangement and parallel divergence channels. The thermal performance and pressure drop characteristics were evaluated under identical operating conditions, including a constant mass flow rate of 3.925 × 10⁻⁴ kg/s and a uniform heat flux of 90 W/cm². The results indicated that the radial microchannel configuration significantly enhanced both hydrodynamic and thermal performance compared with the parallel divergence design. Specifically, the pressure drop was reduced by approximately 32.5%, the overall performance index increased by about 1.5, and improved temperature uniformity across the heat sink was achieved. These findings demonstrate the superiority of the radial microchannel arrangement for high-heat-flux thermal management applications.