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Mekanika: Majalah Ilmiah Mekanika
Published by Universitas Sebelas Maret
ISSN : 14127962     EISSN : 25793144     DOI : https://doi.org/10.20961/mekanika
Core Subject :
"Mekanika: Majalah Ilmiah Mekanika" is an open-access journal published by Mechanical Engineering Study Program, Faculty of Engineering, Universitas Sebelas Maret. Mekanika invites scholars, researchers and practioners who have interest in mechanical engineering to publish their articles and also provides forums for them to share their works and knowledge. Mekanika focuses on the area of materials engineering and science, design, energy, manufacturing and construction but is not limited to. Both English and Bahasa are accepted in this journal. Mekanika has two issues every year (March and September) and aims to publish more frequently in the future.
Arjuna Subject : Teknik (semua kategori) - Teknik Mesin
Articles 75 Documents
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Design of Airscrew Propeller as an Alternative Main Propulsion for Wing in Surface Effect (WiSE) A2C Using the Simplified Method Approach Sasmito, Cahyo; Pujiwat, Rutma; Priatno, Dany Hendrik; Iskendar, Iskendar; Khoirudin, Muh Hisyam; Eskayudha, Dimas Bahtera
Mekanika: Majalah Ilmiah Mekanika Vol 23, No 2 (2024): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v23i2.77937

Abstract

This study focused on developing an airscrew propeller as an alternative propulsion system for the Wing in Surface Effect (WiSE) A2C, employing a rigorous and systematic scientific approach. The design and calculation methodology were grounded in the "simplified method" introduced by Hovey. This technique has proven effective for preliminary propeller design despite its reliance on several assumptions and simplifications. This method balances practicality with empirical data, offering a straightforward framework for generating initial design parameters without extensive computational demands. Although the simplified method has limitations, such as its dependence on empirical observations and reduced computational precision, it remains effective for developing foundational design concepts. The study leveraged this approach to create a propeller design that aligns with the aerodynamic and performance requirements specific to the WiSE A2C. The resulting design features an airscrew propeller with an RAF-6 airfoil profile and a diameter of 685 mm. The RAF-6 profile was chosen for its favorable aerodynamic characteristics, including a high lift-to-drag ratio, which is crucial for optimizing propulsion efficiency. This tailored design ensures compatibility with the operational environment of the WiSE A2C, enhancing its overall performance and stability while meeting specific aerodynamic goals.
Enhancing Ship Stability: A Comparative Analysis of Single and Double Chine Hull Configurations of Semi-Planning Hull at High Speed Ghyferi, Andi Abdullah; Bahatmaka, Aldias; Naryanto, Rizqi Fitri; Won, Lee Sang; Cho, Joung Hyung
Mekanika: Majalah Ilmiah Mekanika Vol 23, No 2 (2024): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v23i2.90734

Abstract

Ship stability could be considered one of the defining aspects of marine transport, as it directly influences the safety and performance of the ship. Past works have found hull geometry critical in the stability issue; however, the impact of various Chinese configurations under different operation scenarios is missing. This paper seeks to address this gap by studying the effects of Chinese single and double geometries on stability, primarily concerning trimming by stern angles in compliance with the High-Speed Craft (HSC) 2000. Annex 8: Monohull Intact Stability Criteria. Stability calculations using Maxsurf software were done concerning angles of the steady heel, the area under the righting levers (GZ) curve, maximum GZ, and initial transverse metacentric height (GMt). The study showed that both Chinese configurations conformed to the prescribed stability standards. Still, the double Chinese configuration showed better results in terms of stability at a 2-degree heel angle, with a GZ value of 1.692 and the highest GMt value in a steady state. Therefore, the research establishes enhanced stability benefits that the users stand to benefit from by adopting double chine configurations relative to single chine styles.
Hydrodynamic Performance Assessment of Straight and Helical Hydrokinetic Turbine Hydrofoil-Blade Sections in River Oyun, North-Central Nigeria Ladokun, Laniyi Laniran
Mekanika: Majalah Ilmiah Mekanika Vol 23, No 2 (2024): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v23i2.92527

Abstract

The performance of lift-based hydrokinetic rotor turbines usually depends on the blade sections or hydrofoil profile. Different hydrofoil blade sections, having different profiles and geometries, give different coefficients of performance in different hydrodynamic settings. This study examined the influence of blade geometry on the power stage characterization of vertical axis crossflow hydrokinetic turbines under conditions of low river current velocity. Two turbines have been selected to characterize the power stage. Pre-developed straight-bladed National Advisory Committee for Aeronautics (NACA) 0021 hydrofoil blade sections and a Gorlov helical/curved NACA 0021 pattern were used in the hydrodynamic experimental characterization along River Oyun, Kwara State, North-Central Nigeria. The graphical ratio of the coefficient of performance, CP,which measures the efficiency of the turbine blade sections converting kinetic energy into mechanical energy, and the turbine blade Tip Speed Ratio (TSR), was used to analyze the hydrodynamic blade performance characterization. The peak CP values, the optimal TSR, the CP curve shape, and the stall regions from the CP-TSR chart were used to determine the hydrofoil with optimal performance.
3D Digital Tomography Image Reconstruction to Determine the Dimensions of Discontinuities in the Material Using MATLAB Azri, Muhammad Farid; Istanto, Iwan; Ismail, Ismail; Astriani, Yuli
Mekanika: Majalah Ilmiah Mekanika Vol 23, No 2 (2024): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v23i2.85293

Abstract

To acquire more accurate information, such as the existence of discontinuities on an object from 2D digital radiography images, a reconstructed 3D image using a tomography technique is needed. In this paper, an algorithm was developed to determine the discontinuity dimension. The object used in this study is made of gypsum, which has three types of artificial discontinuities: a 4.80 mm iron ball, an 8.00 mm iron ball, and drill holes. The processes to get projection data consist of preprocessing to convert the images from red-green-blue to grayscale image format, segmentation to differentiate the object from the background using the Thresholding method and Active Contour Chan-Vese model, and morphological operations to visualize the image into 3D volumetric, followed by determining object dimensions, and subsequently the reconstruction results. The tomographic image reconstruction was constructed from 90 images irradiated by an x-ray machine using digital radiography with constant irradiation parameters and a 2° rotational angle increment interval from 0°-180°. The error results of 4.80 mm iron balls discontinuity are 1.5%, 8.00 mm iron balls are 4.1%, and drill holes are 7.05%. Moreover, the Misclassified Area-Mutual Overlap (MMO) method is employed to test the segmentation results, which resulted in an MMO value of 78.23%.
Analysis of Variations in Bow Design and Vessel Speed on the Response Amplitude Operator (RAO) of a Crew Boat Using Computational Fluid Dynamics (CFD) Kirana, Arnova Chandra Cahya; Bahatmaka, Aldias; Malsyage, Dina; Cho, Joung Hyung; Ttum, Seo Ou
Mekanika: Majalah Ilmiah Mekanika Vol 24, No 2 (2025): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v24i2.106779

Abstract

The performance and stability of crew boats in dynamic maritime environments are significantly influenced by hull geometry, particularly the design of the bow. This study investigates the influence of various elliptical bulbous bow configurations and vessel speeds on the Response Amplitude Operator (RAO) in heave and pitch motions. Using Computational Fluid Dynamics (CFD) simulations via ANSYS AQWA, four bow configurations, including a bare hull and three bulbous bow variants, were analyzed at speeds of 6, 12, and 18 knots under regular wave conditions defined by the Joint North Sea Wave Project (JONSWAP) spectrum. To validate the accuracy and reliability of the simulation method employed in this study, a comprehensive validation procedure was undertaken. For heave motion, the RAO deviation was 3.71%, and for pitch, 4.59%, both within acceptable CFD validation standards. Results indicate a minimal impact at lower speeds; however, at 18 knots, Bow 3 achieved the most significant reduction in RAO, with reductions of up to 9% in heave and 22.4% in pitch. These findings confirm the importance of optimized bow geometry in enhancing seakeeping performance.
Analisys of Tensile Strength, Wear Rate, and Cristallinity of Biocomposite Nano-HA/Magnesium/Shellac Reinforced Cantula Fiber for Bone Screw Material Utami, Dea Pawestry; Triyono, Joko; Raharjo, Wijang Wisnu; Tritjahjono, Rachmad Imbang
Mekanika: Majalah Ilmiah Mekanika Vol 23, No 1 (2024): MEKANIKA: Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v23i1.71127

Abstract

Accidents are a major cause of fractures in Indonesia. One of the treatments for fractures is bone screws with support plates that are placed on broken bone. Currently, many biomaterials for bone screws are being developed which have biodegradable properties so that post-operative bone healing is not required. The purpose of this study was to determine the effect of cantula fiber addition on tensile strength, wear rate, and crystallinity of nano-HA/magnesium/shellac bio-composite for bone screw materials. Nano-HA/magnesium/shellac/cantula fiber materials were mixed using a blender. The material was mixed with a magnesium/hydroxyapatite ratio of 70/30 and cantula fiber was added with variations of 0%, 10%, 20% and 30% of total volume. After that, material mixture was compacted with a pressure of 300 MPa for 10 minutes. Then sintering process was carried out at temperature of 140 °C for two hours. The results showed that the highest tensile strength value was 7.86 MPa at 30% variation. The lowest wear rate was 0.31 x 10-3 mm3/Nm at 30% variation. The highest crystallinity in X-Ray Diffraction observations was obtained at 30% variation, which was 79.65%.
Hydrodynamic Performance Evaluation of a Double Stage Savonius Turbine on River Ogun, South-Western Nigeria Babatunde, Moses Adeniyi; Ladokun, Laniyi Laniran; Oke, M A
Mekanika: Majalah Ilmiah Mekanika Vol 24, No 2 (2025): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v24i2.104492

Abstract

This study evaluates the hydrodynamic performance of a double-stage Savonius hydrokinetic turbine with a rotor diameter of 0.3m, a rotor height of 0.6m, and a swept area of 0.18 m², designed for deployment in the River Ogun, Southwestern Nigeria. The objective is to assess the turbine's suitability for harnessing energy from low-head rivers. The methodology involved testing the turbine in a riverine environment at selected flow velocities and depths, evaluating its power coefficient (Cp), Tip Speed Ratio (TSR), and power output. The results show that the turbine achieves a maximum Cp of 0.321 at a TSR of 0.5 and a peak power output of 100.9 W at a flow velocity of 1.55 m/s and angular velocity of 5.26 rad/s, and with a cut-in speed of approximately 1.48 m/s. Across all test conditions, the average Cp was approximately 0.3013, indicating an energy conversion efficiency of about 30.1% relative to the total available kinetic power, which is 335.15 W. This result highlights the double-stage Savonius turbine’s capacity to extract energy under ultra-low head and low-velocity conditions efficiently and highlights the importance of optimizing turbine design and operating conditions for improved energy generation efficiency.
Numerical Analysis of Six Degrees of Freedom Motion Response of Trimaran Semi-Submersible Ship Putrananda, Musdika Bagas Satria; Bahatmaka, Aldias; Aryadi, Widya; Puteri, Berliana Ayarent; Hutagalung, Christian Imanuel
Mekanika: Majalah Ilmiah Mekanika Vol 24, No 1 (2025): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v24i1.99057

Abstract

This study examines the motion response characteristics of a trimaran semi-submersible vessel, with a focus on its performance in tourism applications where passenger comfort is a primary concern. Using ANSYS AQWA simulation software, this analysis integrates diffraction and radiation theory with potential flow theory to evaluate the six degrees of freedom (surge, sway, heave, roll, pitch, and yaw) under various wave conditions, including different frequencies and directions based on the Joint North Sea Wave Project (JONSWAP) spectrum. Simulations were performed on waves with heading angles ranging from 0° to 180°. The simulation results were validated based on previous studies both experimentally and numerically. The results show that the sway peaks at 8 m/m for heading angles of 90°, while the surge reaches a maximum of 8 m/m at 0° and 180°. The heave motion resonates between 2.2 rad/s with a peak amplitude of 3 m/m at 90°. Pitch motion at heading angles of 0° reaches 40 °/m at 3.5-4 rad/s. Roll motion remained within acceptable limits (9 °/m), and yaw peaked at 13 °/m at 45° and 135°. These findings suggest that, although the trimaran exhibits stable performance in most motion responses, design improvements are necessary to mitigate excessive pitch motion and enhance passenger comfort in tourism applications.
Influence of Splitter Angle Variations on the Efficiency and Power of Pelton Turbine Duma, Gerard Antonini; Sule, Luther; Indah, Andi Besse Riyani; Baru, Cristian
Mekanika: Majalah Ilmiah Mekanika Vol 25, No 1 (2026): MEKANIKA : Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v25i1.108686

Abstract

The Pelton turbine is a type of impulse turbine engineered to exploit the potential energy of high-pressure, low-flow water. A pivotal component of the Pelton turbine bucket is the splitter, which serves as a separator at the core of the bucket, bifurcating the water-jet flow into two symmetrical segments. The splitter modulates the distribution and trajectory of the water flow after it impacts the bucket surface. This study examined the effects of splitter-angle variations on the efficiency and power of a Pelton turbine. The turbine was designed with 20 ABS blades fabricated using 3D printing technology and assessed under splitter-angle configurations of 15°, 25°, 50°, 75°, 100°, and 125°, as well as in the absence of a splitter. Four discharges (0.000692; 0.000663; 0.000642 and 0.000623 m³/s) and various loads, starting from 0.2 to 3.0 kg, with a range of 0.2, were tested. The findings indicate that the splitter angle profoundly affects turbine efficiency, with the 50° angle producing the highest efficiency and power of 89% and 24 W, respectively, at a load of 2.0 kg, a turbine rotation of 285 rpm, and a torque of 0.8044 Nm, with a discharge of 0.000692 m³/s. The experimental and simulation results emphasize the importance of optimizing the splitter geometry to improve energy conversion efficiency and overall turbine performance.
Effect of Boundary Condition on Numerical Study of UAV Composite Skin Panels Under Dynamic Impact Loading Wiranto, Ilham Bagus; Saraswati, Sherly Octavia; Alfikri, Iqbal Reza; Chairunnisa, Chairunnisa; Megawanto, Fadli Cahya; Adhynugraha, Muhammad Ilham; Majid, Nur Cholis
Mekanika: Majalah Ilmiah Mekanika Vol 23, No 1 (2024): MEKANIKA: Majalah Ilmiah Mekanika
Publisher : Universitas Sebelas Maret

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20961/mekanika.v23i1.77875

Abstract

In this study, a dynamic impact loading using Finite Element Analyses (FEA) was applied to an Unmanned Aerial Vehicle (UAV) composite skin panel. Two types of boundary condition panels were investigated (Fixed and Pinned). The composite UAV skin panel consists of upper panel and stiffener which have a thickness of 3 mm and 2 mm, respectively. The material properties used in this study was referring to Hexcel W3G282-F593 technical data sheet. A hemispherical steel indenter with 70 mm diameter and 120 kg of mass was used to crush the panel with a velocity of 4.43 m/s. The finite element analyses were performed using dynamic explicit solver in ABAQUS 6.23. At the beginning of study, the mesh convergence study was conducted to choose the proper mesh for main analysis. The convergence study was simulated using 20 kg mass to shorten computational time. The mesh size of 10 mm was chosen for the main analysis due to convergent result and short computational time compared to others mesh size. The impact deformation, contact force-displacement plot, and contact force-time plot was used to show the differences of using those boundary condition. The results show that fixed and pinned boundary condition reaches its contact force peak with the value of 29.2 kN and 22.8 kN, respectively.

Page 5 of 8 | Total Record : 75

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