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All Journal Teknomekanik Journal of Engineering Researcher and Lecturer
Rahmat Azis Nabawi
Department of Mechanical Engineering, Faculty of Engineering, Universitas Negeri Padang, Indonesia
Chemical Engineering, Chemistry & Bioengineering Education Engineering Mechanical Engineering

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Hydrodynamic optimization of a Sweptback Stern Foil for resistance reduction in flat-hull ships: A CFD-based extension of the Hull Vane concept Rahmat Azis Nabawi; Budi Syahri; Yogi Dian Alfana; Donny Fernandez
Teknomekanik Vol. 9 No. 1 (2026): Regular Issue
Publisher : Universitas Negeri Padang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/teknomekanik.v9i1.54872

Abstract

Flat-hull ships are known to have higher resistance than streamlined hulls. Although the Hull Vane® concept has been proven effective as a stern-mounted energy-saving device through pressure-field modification and stern-wave interaction, most previous studies have focused on straight-foil configurations (straight planform). The effect of planform shape optimization, particularly the sweptback configuration, on the hydrodynamic performance of flat-hull ships is limited in the literature. This study modifies the geometry of a Hull Vane® into a sweptback stern foil and evaluates its performance using Computational Fluid Dynamics simulations. The results show that a 15° sweptback angle yields the greatest reduction in total drag. Velocity contour analysis shows a narrower wake and a more uniform velocity-gradient distribution in the stern area for the 15° swept-back stern-foil configuration compared to other configurations. Meanwhile, the turbulence length distribution shows a tendency toward reduced intensity of large-scale turbulent structures behind the ship, indicating improved wake-flow characteristics. The identified drag reduction mechanism primarily stems from improved pressure recovery and modified pressure distribution in the stern area, which is consistent with the working principle of Hull Vane®. Optimizing the sweptback planform geometry yields more efficient flow interaction than the straight-foil configuration. These findings indicate that planform optimization is an important design parameter in the development of stern foils to improve the hydrodynamic efficiency of medium-to high-speed commercial vessels.
Loading-dependent mechanical performance of alkali-treated areca nut husk fiber reinforced polyester composites modified with Uncaria gambir extract Rahmat Azis Nabawi; Syahril Syahril; Hairul Abral
Teknomekanik Vol. 8 No. 2 (2025): Regular Issue
Publisher : Universitas Negeri Padang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/teknomekanik.v8i2.52472

Abstract

Natural fiber-reinforced polymer composites often experience mechanical performance limitations due to weak interfacial bonds between hydrophilic fibers and hydrophobic matrices. This study experimentally examined the effect of alkali treatment and modification using Uncaria gambir extract (UGE) on the mechanical properties and interface morphology of polyester composites reinforced with areca nut husk fiber (ANHF). Four composite configurations were prepared with a constant fiber weight fraction of 40 wt.% after alkali treatment using 6% NaOH for 24 hours, while the remaining 2 wt.% UGE was selectively applied as a fiber surface treatment, matrix additive, or a combination of both. Tensile and flexural properties were evaluated in accordance with ASTM standards, while interface morphology was examined using scanning electron microscopy (SEM). The results showed that alkali-treated composites without UGE addition had the highest tensile strength, which was attributed to increased fiber surface roughness and mechanical interlocking mechanisms. Conversely, fiber surface modification using UGE significantly increased flexural strength, indicating better stress distribution under flexural loading due to increased interface continuity. However, the addition of UGE to the matrix caused a decrease in tensile strength, which was thought to be related to a reduction in matrix stiffness. SEM observations confirm the presence of distinct interface morphology differences according to the treatment applied. These findings indicate that UGE serves primarily as a bio-based interfacial modifier, enhancing flexural performance, while its effectiveness is strongly governed by the mechanical loading mode.
A concave impeller: A new modified semi-open impeller for higher performance of centrifugal pumps Rahmat Azis Nabawi; Egi Fadillah; Haris Shiddiq Mulyadi; Muhammad Shadiq Fahrezi; Firza Fernanda Putra
Journal of Engineering Researcher and Lecturer Vol. 4 No. 1 (2025): Regular Issue
Publisher : Researcher and Lecturer Society

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.58712/jerel.v4i1.178

Abstract

The performance enhancement of centrifugal pumps is continuously pursued to meet increasingly complex operational demands. Ongoing improvements in pump component design, particularly the impeller, are essential to achieving optimal configurations. The impeller is a critical component that significantly influences the overall performance of centrifugal pumps. This study aims to develop an impeller design that offers higher performance compared to the original one. The methodology utilized was Computational Fluid Dynamics (CFD). The primary focus was on modifying the semi-open impeller type. Two modified impellers were developed with concave and convex design. They were simulated and compared to the original impeller configuration. The simulation results indicate that pressure distribution at the inlet remains similar for all designs. However, pressure variations at the outlet and differences in volumetric flow rate between inlet and outlet were found. The contour visualization of pressure and flow velocity for each impeller configuration shown from the CFD simulation results is further discussed, in terms of pressure distribution and flow trajectory pressure.
Co-Authors Budi Syahri Donny Fernandez Egi Fadillah Firza Fernanda Putra Hairul Abral Haris Shiddiq Mulyadi Muhammad Shadiq Fahrezi Syahril Syahril Yogi Dian Alfana