2026-07-13T10:59:49+03:30 http://ijmt.ir/browse.php?mag_id=47&slc_lang=en&sid=1

47-847 2026-07-13 10.1002

International Journal of Maritime Technology ijmt 2345-6000 2476-5333 10.66224/ijmt 2025 21 1 mojtaba pakian pakianm@chmail.ir The engine braking power moves the ship and it is converted into effective power by taking into account the propulsion power losses and the propeller efficiency. The braking power diagram must be in a suitable position relative to the continuous power diagram and the maximum power of the engine to ensure safe engine operation. In this paper, the propulsion system of a catamaran passenger vessel is investigated and the matching condition of the propulsion components in two shaft line designs and their impact on the performance of the engine and vessel are analyzed in detail. The hull is subjected to CFD analysis and the resistance is calculated. Then, using the hydrodynamic coefficients of the propeller, the matching calculations of the propeller to the engine have been done.  To match the propulsion system, the gearbox with 2.963:1 was coupled with the shaft line. The shaft line design is satisfactory in ship maneuvering and diesel engine performance. The ship's resistance was calculated by STAR-CCM+ software, used in matching calculations and the results have been validated by sea trials. The error between sea trial and matching calculations is a maximum of 7%. Matching of Propulsion System Diesel engine Propeller Overload Over speed 2025 1 01 1 10 http://ijmt.ir/article-1-847-en.pdf 10.61882/ijmt.21.1.1

47-850 2026-07-13 10.1002

International Journal of Maritime Technology ijmt 2345-6000 2476-5333 10.66224/ijmt 2025 21 1 Seyed Reza Samaei samaei@srbiau.ac.ir Mohammad Asadian Ghahfarokhi m.asadian@srbiau.ac.ir High-speed monohull vessels with chine hulls are widely used due to their simple design, but maintaining optimal performance at high speeds requires precise hull force analysis. This study utilizes 3D scanning to capture hull geometry, refining it in AutoCAD for efficiency. Hydrostatic and hydrodynamic assessments are conducted using Maxsurf, applying the Switkowski method. The study examines vessel motion, crew comfort, and water ingress under different sea conditions. Results indicate that at a 5.4-degree trim, pitch motion intensifies in harmonic waves, yaw motion increases in beam waves, and pitch and heave motions are more pronounced in head waves. Water ingress becomes a concern at this trim in Beaufort 2 and 3, with MSI peaking at 12.5% in Beaufort 3. The lowest resistance occurs at 5.22 knots, but higher trims raise power demands. Manual trim adjustments using outboard engines and jacks effectively mitigate these effects. high-speed vessel hydrostatics hydrodynamics crew sea conditions water ingress 2025 1 01 12 27 http://ijmt.ir/article-1-850-en.pdf 10.61882/ijmt.21.1.12

47-851 2026-07-13 10.1002

International Journal of Maritime Technology ijmt 2345-6000 2476-5333 10.66224/ijmt 2025 21 1 Seyed Reza Samaei samaei@srbiau.ac.ir Mohammad Asadian Ghahfarokhi m.asadian@srbiau.ac.ir The demand for high-speed crafts has grown rapidly due to their strategic importance and quick response capabilities. Governments prioritize their development through research and industry advancements. Designing a high-speed craft exceeding 60 knots requires significant time and cost. This study identifies key factors for optimizing speed and maneuverability through hull modifications, chine positions, indentations, propulsion systems, and initial trim adjustments. The sample craft was 3D scanned, and simulations were conducted using MAXSURF. The hull was modified and uniformly adjusted, followed by hydrostatic and hydrodynamic calculations. Findings indicate that achieving speeds above 60 knots require a minimum initial trim of 0.4° at the transom. Proper hull line adjustments and equipment placement were essential. Additionally, with a safety factor of 1.25, the craft requires approximately 600 horsepower for the desired speed. These optimizations ensure efficient performance while minimizing costs.   High-speed craft hydrostatics maneuverability fiberglass boat trim angle 2025 1 01 28 43 http://ijmt.ir/article-1-851-en.pdf 10.61882/ijmt.21.1.28

47-859 2026-07-13 10.1002

International Journal of Maritime Technology ijmt 2345-6000 2476-5333 10.66224/ijmt 2025 21 1 Mohammad Amin Esabat m.amin.esabat@gmail.com Ahmadreza Kohansal kohansal@pgu.ac.ir The purpose of this paper was to numerically investigate the effects of using supercavitation sections in ventilated semi-submerged hydrofoils. Studying the flow around such hydrofoils is often very complicated due to its multiphase nature and the simultaneous occurrence of cavitation and ventilation phenomena. The desired foil was the Waid section foil which has been examined at different attack angles and for different cavitation numbers. In this numerical simulation, the RANSE finite volume solver along with the VOF method have been used to model the multiphase flow around the semi-submerged hydrofoil. According to the obtained results, the formation of cavitation bubbles and the formation of ventilation around a supercavitating section is different from the conventional sections in semi-immersed foils. This could be due to the specific geometric shape of the supercavitating sections, especially in their front area. The pressure and flow contours around the hydrofoil have been predicted in semi-submerged form, and the ventilating air flow around the hydrofoil has also been investigated. Also, it has shown that the effect of cavitation at high speeds causes the formation of continuous bubbles, which will lead to the reduction of drag coefficients and increase the efficiency of supercavitating hydrofoils. According to the results obtained in this simulation, by increasing the cavitation number, the drag coefficient also increases in proportion to the lift coefficient. This process continues until the foil enter the completely wet phase, which with this phase change, the lift-to-drag coefficient ratio also decreases. Therefore, due to its high efficiency, the Waid section, is recommended for the design of surface piercing hydrofoils. Super-cavitation Hydrofoil Surface piercing Ventilation 2025 1 01 44 53 http://ijmt.ir/article-1-859-en.pdf 10.61882/ijmt.21.1.44

47-871 2026-07-13 10.1002

International Journal of Maritime Technology ijmt 2345-6000 2476-5333 10.66224/ijmt 2025 21 1 MohammadHussein Qaedsharaf mqaed1100@gmail.com Ehsan Yari Ehsanyari11@gmail.com Mojtaba Dehghan Manshadi dehghanmanshadi@gmail.com This study investigates the effect of duct inlet length on the hydrodynamic performance of a pre-swirl pump-jet system, focusing on open water efficiency through uncertainty analysis. To this end, five models with varying duct inlet lengths (0~0.1DRotor) were experimentally tested in the cavitation tunnel at Imam Khomeini Naval University in Noshahr. Sampled parameters included rotor thrust, combined duct and stator thrust, and rotor torque at eight advance ratios (J). Each measurement was repeated four times, and their averaged values were utilized in the calculations. Sensitivity analysis revealed that torque has a more significant impact on open-water efficiency compared to total thrust. Experimental test results demonstrated that the open water efficiency for all configurations reached a maximum at J=1.1. The L=0.1DR configuration exhibited the highest efficiency at 62.15%, representing a 5.15% improvement over the L=0DR configuration. The relative uncertainty of efficiency was below 5%, and the L=0.1DR configuration showed the smallest uncertainty range, indicating high experimental precision. Furthermore, an examination of the open water efficiency uncertainty range revealed that for advance ratios of 0.6, 1.1, and 1.4, the L=0.1DR configuration yielded the widest efficiency range. The upper bound of open water efficiency also belonged to the L=0.1DR configuration for other advance ratios. Therefore, based on the results of the conducted uncertainty analysis, the L=0.1DR configuration demonstrates improved open water efficiency performance compared to other configurations. This improvement is attributed to increased thrust resulting from better uniformity of the flow entering the stator and optimized angle of attack to the rotor blades.   Pre-swirl PumpJet Duct Inlet Length Stator-Rotor Distance Hydrodynamic Performance Open-Water Efficiency Uncertainty Analysis 2025 1 01 54 70 http://ijmt.ir/article-1-871-en.pdf 10.61882/ijmt.21.1.54

47-869 2026-07-13 10.1002

International Journal of Maritime Technology ijmt 2345-6000 2476-5333 10.66224/ijmt 2025 21 1 Poorya Khorsandi pooryakhorsandy7900@gmail.com Ahmad Hajivand hajivand@kmsu.ac.ir This paper introduces an innovative, AI-driven methodology for predicting ship resistance using only three fundamental input parameters: Length Between Waterlines (LWL), Beam at Waterline (BWL), and Draft (T). Traditional resistance prediction techniques such as empirical methods, towing tank experiments, and computational fluid dynamics (CFD) simulations are highly accurate but involve significant time, cost, and complexity. Our approach leverages machine learning algorithms, including XGBoost, CatBoost, and Gradient Boosting, to derive a comprehensive suite of hydrodynamic characteristics from a robust dataset comprising 308 full-scale experiments across 22 different hull shapes. The methodology begins with meticulous data preprocessing and feature engineering, including normalization, outlier analysis, and correlation assessment, to ensure reliability and minimize error propagation. By transforming raw hydrodynamic data into dimensionless groups, our models effectively capture both linear and non-linear relationships among critical parameters such as displacement, wetted surface area, midship section area, waterplane area, and the longitudinal center of buoyancy (LCB). Simple linear regression techniques were successfully used to derive parameters with perfect correlations, while more complex non-linear interactions were accurately predicted using advanced ensemble methods. The integration of these AI models into a Django-based web application further enhances the utility of our approach, providing naval architects and marine engineers with a user-friendly, real-time tool for design optimization and performance evaluation. Comparative analysis indicates that our streamlined model delivers predictions of residual and frictional resistance with accuracy comparable to traditional methods, while offering significant improvements in computational efficiency and cost-effectiveness. Overall, this research bridges the gap between classical hydrodynamic theory and modern artificial intelligence techniques, offering a rapid, reliable, and scalable solution for ship resistance prediction that has the potential to significantly enhance early-stage design processes in naval architecture. Ship Resistance Hydrodynamic Parameters Artificial Intelligence Machine Learning Correlation Analysis Ensemble Methods Design Optimization 2025 1 01 71 79 http://ijmt.ir/article-1-869-en.pdf 10.61882/ijmt.21.1.71