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All Journal Mekanika: Majalah Ilmiah Mekanika
Kirana, Arnova Chandra Cahya
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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.
Finite Element-Based Evaluation of Double-Hull Midsection Performance under Oblique Collision Malsyage, Dina; Bahatmaka, Aldias; Kirana, Arnova Chandra Cahya; Won, Lee Sang; Hee, Song Yeon
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.v24i2.106778

Abstract

Ship collisions pose a significant concern in maritime safety, particularly for double hull vessels operating in confined or high-risk areas. Understanding the structural response to collision is essential for improving crashworthiness. This study investigates the safety limits of a double-hull midsection ship under oblique impacts. Finite Element Analysis (FEA) was used to simulate three collision angles (45°, 60°, 90°) and four velocities (1, 3, 5, and 7 m/s). A benchmark study confirmed simulation accuracy with an error of less than 2%. The study reveals that impact angle and velocity significantly affect the ship's structural response. Perpendicular impacts (90°) with varying velocities produce the highest internal energy, reaching up to 28.99 MJ. In oblique impacts at 45°, the highest crushing force was generated, which reached 51.05 MN. Safety factor analysis indicates that impacts exceeding 3 m/s, especially those approaching perpendicular, lead to a decrease in structural integrity, falling below the acceptable limit. At 7 m/s and 90°, the stress on the inner hull exceeds the material's ultimate strength, indicating a potential for failure. To ensure structural safety, operational speeds should be limited to below 3 m/s. Findings highlight the importance of managing collision risks and guiding future ship design optimization.
Co-Authors Aldias Bahatmaka Cho, Joung Hyung Hee, Song Yeon Malsyage, Dina Ttum, Seo Ou Won, Lee Sang