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Experimental and Theoretical Investigation of Trim Tab Effects on Hydrodynamic Resistance and Planning Performance of High-Speed Planning Vessels 2 2 This study presents a comprehensive experimental investigation into the hydrodynamic performance of high-speed planning vessels equipped with adjustable trim tabs. Two scaled 40-foot beam-type models were tested under controlled towing tank conditions to assess the effects of trim angle variations on resistance, dynamic stability, and transition into the planning regime. The tests evaluated both untrimmed and trimmed configurations using multiple trim tab heights, measuring resistance forces, trim behavior, and planning onset velocities. Results demonstrate that optimal trim tab deployment significantly reduces hydrodynamic resistance, lowers the Hump Resistance Region, and enhances vessel stability at critical speeds. Trim tab configuration “B” showed superior performance, enabling earlier planning transition with lower power demand and reduced bow impact. Additionally, this study addresses model scaling effects, construction tolerances, and control system calibration to ensure fidelity with full-scale vessel behavior. The findings underscore the importance of trim tab integration in the design of modern high-speed vessels, offering practical insights for resistance minimization, propulsion efficiency, and structural safety in dynamic marine environments.   1 13 2025/06/2 1404/3/12 2025/09/28 1404/7/6 Seyed Reza Samaei Seyed Reza Samaei Assistant professor, Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran ایران samaei@srbiau.ac.ir Mohammad Asadian Ghahfarokhi Mohammad Asadian Ghahfarokhi Assistant professor, Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran; ایران m.asadian@srbiau.ac.ir High-speed vessels Trim tab optimization Hydrodynamic resistance Planing performance Experimental model testing Towing tank analysis Beam-type hulls Resistance reduction Trim angle effects Marine propulsion efficiency Brown, P. W. (1971). 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A., Velgaard, A., & Aasheim, I. (2009). Performance of a planning craft with mid-mounted interceptor. In Fast 2009, Greece, October 2009.##Hansvic, T. (2005). Resistance of planning catamaran with step (MSc thesis). Department of Marine Technology, NTNU, Trondheim, Norway.##Hansvic, T., & Steen, S. (2006). Use of interceptors and stepped hull to improve performance of high-speed planning catamaran. In Int. Conf. on High-Speed Craft-ACV's, RINA, London, 2006.##Fridman, G. (1969). Theory and practice of application of the interceptors on high-speed ships. In Fast 2007, Shanghai.##Chambliss, D. B., & Boyd, G. M., Jr. (1953). The planning characteristics of two V-shaped prismatic surfaces having angles of deadrise of 20° and 40°. NACA TN No.2876, January 1953.##Savirsky, D., & Neidlinger, J. W. (1954). Wetted area and center of pressure of planning surfaces at very low speed coefficients. 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(2009). The Effect of Spray Rails and Transverse Steps on High-Speed Vessels (Master's thesis).##Seyed Reza Samaei, Madjid Ghodsi Hassanabad, Mohammad Asadian ghahfarrokhi, Mohammad Javad Ketabdari, "Numerical and experimental investigation of damage in environmentally-sensitive civil structures using modal strain energy (case study: LPG wharf)". Int. J. Environ. Sci. Technol. 18, 1939-1952 (2021).##Samaei, S. R., Azarsina, F., & Ghahferokhi, M. A. (2016). Numerical simulation of floating pontoon breakwater with ANSYS AQWA software and validation of the results with laboratory data. Bulletin de la Société Royale des Sciences de Liège, 85, 1487-1499.##Samaei, S. R., Asadian Ghahferokhi, M., & Azarsinai, F. (2022). Experimental study of two types of simple and step floating pontoon breakwater in regular waves. International Journal of Marine Science and Environment, 6(1), 8-16.##Samaei, S. R., & Ghodsi Hassanabad, M. (2022). Damage location and intensity detection in tripod jacket substructure of wind turbine using improved modal strain energy and genetic algorithm. Journal of Structural and Construction Engineering, 9(4), 182-202. https://doi: 10.22065/jsce.2021.294103.2488##Samaei, S. R., Ghodsi Hassanabad, M., Asadian Ghahfarrokhi, M., & Ketabdari, M. J. (2021). Numerical and experimental study to identify the location and severity of damage at the pier using the improved modal strain energy method-Case study: Pars Asaluyeh LPG export pier. Journal of Structural and Construction Engineering, 8(Special Issue 3), 162-179. https://doi: 10.22065/jsce.2020.246425.2225##Samaei, S. R., Ghodsi Hassanabad, M., Asadian Ghahfarrokhi, M., & Ketabdari, M. J. (2020). Structural health monitoring of offshore structures using a modified modal strain energy method (Case study: four-leg jacket substructure of an offshore wind turbine). Journal Of Marine Engineering, 16(32), 119-130.##Samaei, S. 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Machine Learning Models Development to Predict Corroded Pipeline Behavior Considering Defects Interaction 2 2 Internal corrosion poses a significant risk to offshore pipeline operations. This study aims to utilize a combination of the Finite Element Method (FEM) and Latin Hypercube Sampling (LHS) to create a database of structural response data for corroded pipelines experiencing longitudinally interacting internal corrosion defects under internal and external pressure loading. The database includes input data such as pipeline geometry parameters, pipeline material data, corrosion defect data and loading data. This generated database will be utilized to train various advanced machine learning (ML) models to develop a predictive model capable of estimating the Maximum von Mises Stress occurring in the outermost mesh layer of a mesh ligament within the thickness of the corroded pipeline at the defected area. Such predictive capabilities of the ML model will enhance the ability to forecast leakage based on pipeline and defect specifications, thereby saving costs and time. To achieve the optimal model, various ML algorithms have been compared. Finally, to assess the prediction accuracy of the models, results of models were compared and evaluated.   14 31 2025/06/22025/08/19 1404/5/28 2025/09/282025/10/8 1404/7/16 Soheyl Hosseinzadeh Soheyl Hosseinzadeh University of Tehran ایران s_hosseinzadeh@ut.ac.ir Mohammad Reza Bahaari Mohammad Reza Bahaari University of Tehran ایران mbahari@ut.ac.ir Mohsen Abayni Mohsen Abayni University of Tehran ایران mohsen.abyani@ut.ac.ir Offshore Pipeline Engineering Pipeline Integrity Management Structural Reliability Random Sampling Latin Hypercube Sampling Machine Learning Hosseinzadeh S, Gatmiri B. Bearing behavior assessment of wind turbines' s shallow foundations, comparison of gravity-based foundations and suction buckets. Ocean Syst Eng [Internet]. 2025 [cited 2025 Oct 5];15(3):241. Available from: http://techno-press.org/content/?page=article&journal=ose&volume=15&num=3&ordernum=1##Sampath S, Bhattacharya B, Aryan P, Sohn H. A Real-Time, Non-Contact Method for in-Line Inspection of Oil and Gas Pipelines Using Optical Sensor Array. Sensors. 2019;19(16):3615.##Demoz A, Papavinasam S, Omotoso O, Michaelian K, Revie RW. Effect of Field Operational Variables on Internal Pitting Corrosion of Oil and Gas Pipelines. Corrosion. 2009;65(11):741-7.##Colindres SC, Méndez GT, Velázquez JC, Cabrera-Sierra R, Angeles-Herrera D. Effects of Depth in External and Internal Corrosion Defects on Failure Pressure Predictions of Oil and Gas Pipelines Using Finite Element Models. Adv Struct Eng. 2020;##Rachman A, Zhang T, Chandima Ratnayake RM, Ratnayake RMC. Applications of Machine Learning in Pipeline Integrity Management: A State-of-the-Art Review. Int J Press Vessel Pip. 2021 Oct 1;193:104471.##Zheng Y, Zhang Y, Lin J. System reliability analysis for independent and nonidentical components based on survival signature. Probabilistic Eng Mech. 2023 Jul 1;73:103466.##Wang Y, Wharton JA, Shenoi RA. Mechano-electrochemical modelling of corroded steel structures. Eng Struct. 2016 Dec 1;128:1-14.##Yang Y, Wang GH, Qu Z, Zhang H, He J, Chen H. Reliability Analysis of Gas Pipeline With Corrosion Defect Based on Finite Element Method. Int J Struct Integr. 2021;##Cheng YF. Pipeline Corrosion. Corros Eng Sci Technol Int J Corros Process Corros Control. 2015;50(3):161-2.##Abyani M, Bahaari MR. A new approach for finite element based reliability evaluation of offshore corroded pipelines. Int J Press Vessel Pip. 2021 Oct 1;193:104449.##Vamvatsikos D, Allin Cornell C. Incremental dynamic analysis. Earthq Eng Struct Dyn [Internet]. 2002 Mar 1 [cited 2023 Feb 10];31(3):491-514. Available from: https://onlinelibrary.wiley.com/doi/full/10.1002/eqe.141##Mustaffa Z, Gelder P v., Dawotola AW, Yu S, Kim DK. Reliability Assessment for Corroded Pipelines in Series Considering Length-Scale Effects. Int J Automot Mech Eng. 2018;##Kuppusamy CS, Karuppanan S, Patil S. Buckling Strength of Corroded Pipelines With Interacting Corrosion Defects: Numerical Analysis. Int J Struct Stab Dyn. 2016;16(09):1550063.##Xie M, Wang Y, Xiong W, Zhao J, Pei X. A Crack Propagation Method for Pipelines With Interacting Corrosion and Crack Defects. Sensors. 2022;##Arumugam T, Rosli MKAM, Karuppanan S, Ovinis M, Lo M. Burst Capacity Analysis of Pipeline With Multiple Longitudinally Aligned Interacting Corrosion Defects Subjected to Internal Pressure and Axial Compressive Stress. Sn Appl Sci. 2020;2(7).##Zhang H, Sun M, Zhang J, Zhang Y, Li B, Zhai K. Study on Assessment Method of Failure Pressure for Pipelines with Colony Corrosion Defects Based on Failure Location. Process 2023, Vol 11, Page 3134 [Internet]. 2023 Nov 2 [cited 2024 May 25];11(11):3134. Available from: https://www.mdpi.com/2227-9717/11/11/3134/htm##Fekete G, Varga L. Extension of Pit Corrosion Effect on Pipelines. Period Polytech Mech Eng. 2011;55(1):15.##Abyani M, Bahaari MR. Effects of correlation between the adjacent components on time dependent failure probability of corroded pipelines. Struct Infrastruct Eng [Internet]. 2020;0(0):1-14. Available from:##Ossai CI, Boswell B, Davies IJ. Predictive Modelling of Internal Pitting Corrosion of Aged Non-Piggable Pipelines. J Electrochem Soc. 2015;162(6):C251-9.##Nizamani Z, Mustaffa Z, Wen LL. Determination of Extension of Life of Corroded Offshore Pipelines Using Form and Monte Carlo Structural Reliability. 2015;##Hou X, Wang Y, Zhang P, Qin G. Non-Probabilistic time-varying reliability-based analysis of corroded pipelines considering the interaction of multiple uncertainty variables. Energies. 2019;12(10).##Cui J. Studying Corrosion Failure Prediction Models and Methods for Submarine Oil and Gas Transport Pipelines. Appl Sci. 2023;13(23):12713.##Capula Colindres S, Méndez GT, Velázquez JC, Cabrera-Sierra R, Angeles-Herrera D. Effects of depth in external and internal corrosion defects on failure pressure predictions of oil and gas pipelines using finite element models. Adv Struct Eng. 2020 Oct 1;23(14):3128-39.##Abyani M, Karimi M, Shahgholian-Ghahfarokhi D. Failure assessment of corroded offshore pipelines using code-based approaches and a combination of numerical analysis and artificial neural network. Int J Press Vessel Pip [Internet]. 2024;209(April):105194. Available from:##Soomro AA, Mokhtar AA, Kurnia JC, Lashari N, Lu H, Sambo C. Integrity assessment of corroded oil and gas pipelines using machine learning: A systematic review. Eng Fail Anal. 2022 Jan 1;131:105810.##Ossai CI. A Data-Driven Machine Learning Approach for Corrosion Risk Assessment-A Comparative Study. Big Data Cogn Comput [Internet]. 2019 Jun 1 [cited 2025 Jul 20];3(2):1-22. 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Reconciling Per-Capita Water Metrics with Aquifer Stress on Qeshm Island: Pathways for Coastal Blue Economy Development 2 2 Qeshm Island’s extreme aridity and rapid growth expose a mismatch between headline per-capita renewable water figures and actual aquifer stress. Using multi-decadal precipitation, census, and well records, we estimate renewable supply, recharge, storage, and salinity. Natural replenishment is minimal: about 60% of rainfall is lost to evaporation and most of the remainder leaves as runoff, yielding little effective recharge. Under trend-based demographic projections, renewable water per capita declines to 757 m3 per person per year by 2036 (medium evaporation-loss scenario). Groundwater observations show a long-term water-table decline near 0.091 m per year and salinity rising to about 14 to 16.6 dS/m, consistent with persistent overdraft and seawater intrusion or up-coning. To translate hydrologic limits into development choices, we evaluate a conservative 40% withdrawal of renewable yield with a mixed allocation 70% agriculture, 20% industry, 10% domestic. At this intensity the budget can irrigate about 1,523 ha of date palms, support roughly 335,000 t/yr of petrochemical output, and supply about 23,841 residents, generating approximately $16.45 million (agriculture), $334.69 million (industry), and $0.22 million (domestic) per year around $351 million in total. These results show that per-capita indicators alone can overstate security; resilient coastal-marine development on Qeshm will require aligning withdrawals with limited renewability and storage, coupled with managed aquifer recharge, targeted desalination, and selective use of saline groundwater to protect potable supplies and industrial applications requiring low-salinity makeup water (e.g., boiler and cooling systems), where acceptable conductivity is typically ≲0.2–2 dS m⁻¹ with low hardness and silica. 32 47 2025/06/22025/08/192025/08/22 1404/5/31 2025/09/282025/10/82025/11/15 1404/8/24 Emad Mahjoobi Emad Mahjoobi Department of Water and Environmental Engineering, Faculty of Civil Engineering, Shahrood University of Technology ایران emahjoobi@shahroodut.ac.ir Mahan Azizi Mahan Azizi PhD student in Water Resources Engineering and Management, Faculty of Civil Engineering,Shahrood University of Technology ایران mahan.azizi@shahroodut.ac.ir Mohammad Reza Asli Charandabi Mohammad Reza Asli Charandabi PhD student in Water Resources Engineering and Management, Faculty of Civil Engineering,Shahrood University of Technology ایران m.aslicharandabi@shahroodut.ac.ir Groundwater Overdraft Qeshm Island Aquifer Renewable Water per Capita (RWRPC) Salinization Water Scarcity Management Jackson, R.B., et al., Water in a changing world. 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Calatrava, The role of desalinisation to address aquifer overdraft in SE Spain. Journal of Environmental Management, 2014. 144: p. 247-257.##Gorjian, S. and B. Ghobadian, Solar desalination: A sustainable solution to water crisis in Iran. Renewable and Sustainable Energy Reviews, 2015. 48: p. 571-584.##Nesterov, O., An assessment of seawater desalination impact on salinities in the Arabian/Persian Gulf using a 3D circulation model. Ocean Modelling, 2025. 194: p. 102503.##Rafiee, H. and F. Balovi, Paradox of limited water resources in Iran and goals of self-sufficiency in agricultural sector. Preprints, 2017.##Saemian, P., et al., How much water did Iran lose over the last two decades? Journal of Hydrology: Regional Studies, 2022. 41: p. 101095.##Teimoori, M., S.M. Mirdamadi, and S.J. Hosseini, Modeling of climate change effects on groundwater resources: The application of dynamic systems approach. 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Heliyon, 2023. 9(8): p. e18507.##Agency, U.S.E.P., Secondary drinking water standards: Guidance for nuisance chemicals (EPA 816-F-15-002). 2015, U.S. EPA.##Healy, R.W., et al., Water budgets: Foundations for effective water-resources and environmental management (USGS Circular 1308). 2007, U.S. Geological Survey.##Todd, D.K., Groundwater Hydrology. 2008: Wiley.##Konikow, L.F. and J.D. Bredehoeft, Groundwater Resource Development: Effects and Sustainability. 2020: The Groundwater Project.##Noori, R., et al., Decline in Iran's groundwater recharge. Nat Commun, 2023. 14(1): p. 6674.##Lazzarini, M., et al., Urban climate modifications in hot desert cities: The role of land cover, local climate, and seasonality. Geophysical Research Letters, 2015. 42(22): p. 9980-9989.##Hosseinyar, G., et al., Holocene sea-level changes of the Persian Gulf. Quaternary International, 2021. 571: p. 26-45.##Zeynolabedin, A. and R. 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Designing an Optimal PID for Heading Control of a linearized High Speed container ship using Adaptive Particle Swarm Optimization Algorithm 2 2 The reliable control of marine vessels remains a critical challenge due to the nonlinear dynamics and strong environmental disturbances inherent in ocean operations. This paper proposes an optimal heading control strategy for a linearized model of a high-speed container ship based on a Proportional–Integral–Derivative (PID) controller whose parameters are tuned using the Adaptive Particle Swarm Optimization (APSO) algorithm. While classical PID controllers are widely adopted for their structural simplicity and robustness, they often require labor-intensive parameter tuning and exhibit performance degradation under time-varying sea states. To overcome these limitations, the proposed APSO framework adaptively balances global exploration and local exploitation to identify optimal PID gains. The optimization objective function integrates both trajectory-tracking accuracy and control effort, thereby ensuring a trade-off between precision and efficiency. The linear dynamic model of the container ship is formulated and implemented in MATLAB/Simulink, serving as the test platform. Simulation results reveal that the APSO-tuned PID controller achieves substantial improvements in transient and steady-state responses, including overshoot suppression, reduced settling time, and acceptable gain margin, compared with conventional PID tuning. These findings highlight the potential of APSO-based PID design as a robust and interpretable control solution for advanced marine navigation and dynamic positioning applications. 48 54 2025/06/22025/08/192025/08/222025/06/4 1404/3/14 2025/09/282025/10/82025/11/152026/01/4 1404/10/14 Esmat Sadat Alaviyan Shahri Esmat Sadat Alaviyan Shahri Assistant Professor, Electrical and Computer Engineering Department, University of Gonabad, Gonabad, Iran; ایران alaviyan@gonabad.ac.ir Adaptive particle Swarm Optimization (APSO) Fixt Structure control Robust Control Optimal PID a linearized model container ship WANG, C., GAO, X. and WANG, L.,(2025), BESO-PPF: A PPF-optimized ship heading controller based on backstepping control and the ESO, Ocean Engineering, 316, p. 119925.##YE, Y., WANG, Y., WANG, L. and WANG, X.,(2023), A modified predictive PID controller for dynamic positioning of vessels with autoregressive model, Ocean Engineering, 284, p. 115176.##WANG, Y., et al.,(2024), An adaptive PID controller for path following of autonomous underwater vehicle based on Soft Actor-Critic, Ocean Engineering, 307, p. 118171.##ZHAO, S., MU, J., LIU, H., SUN, Y. and CAJO, R.,(2025), Heading control of USV based on fractional-order model predictive control, Ocean Engineering, 322, p. 120476.##WANG, R., LI, X., AHMED, Q., LIU, Y. and MA, X.,(2018), in 2018 Annual American Control Conference (ACC). p. 3908-3914.##EBRAHIMI, M., ALAVIYAN SHAHRI, E. S. and ALFI, A.,(2024), A graphical method-based Kharitonov theorem for robust stability analysis of incommensurate fractional-order uncertain systems, Computational and Applied Mathematics, 43(2), p. 101.##EBRAHIMI, M. and ASGARI, M.,(2021), Robust fractional-order fixed-structure controller design for uncertain non-commensurate fractional plants using fractional Kharitonov theorem, Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 235(8), p. 1375-1387.##ALAVIYAN SHAHRI, E. S. and BALOCHIAN, S.,(2015), A Stability Analysis on Fractional Order Linear System with Nonlinear Saturated Disturbance, National Academy Science Letters, 38(5), p. 409-413.##ALAVIYAN SHAHRI, E. S. and BALOCHIAN, S.,(2016), An analysis and design method for fractional-order linear systems subject to actuator saturation and disturbance, Optimal Control Applications and Methods, 37(2), p. 305-322.##BORASE, R. P., MAGHADE, D. K., SONDKAR, S. Y. and PAWAR, S. N.,(2021), A review of PID control, tuning methods and applications, International Journal of Dynamics and Control, 9(2), p. 818-827.##LEE, D., LEE, S. J. and YIM, S. C.,(2020), Reinforcement learning-based adaptive PID controller for DPS, Ocean Engineering, 216, p. 108053.##GHAMARI, S. M., KHAVARI, F. and MOLLAEE, H.,(2023), Lyapunov-based adaptive PID controller design for buck converter, Soft Computing, 27(9), p. 5741-5750.##ZHAN, S., LIU, Q., ZHAO, Z., ZHANG, S. A. and XU, Y.,(2025), Advanced Robust Heading Control for Unmanned Surface Vessels Using Hybrid Metaheuristic-Optimized Variable Universe Fuzzy PID with Enhanced Smith Predictor, Biomimetics, 10(9), p. 611.##ZHAO, Y.,(2010), in 2010 International Conference on Machine Vision and Human-machine Interface. p. 679-682.##ZHANG, H., ZHAO, Z., WEI, Y., LIU, Y. and WU, W.,(2025), A Self-Tuning Variable Universe Fuzzy PID Control Framework with Hybrid BAS-PSO-SA Optimization for Unmanned Surface Vehicles, Journal of Marine Science and Engineering, 13(3), p. 558.##ALAVIYAN SHAHRI, E. S., ALFI, A. and TENREIRO MACHADO, J. A.,(2019), Fractional fixed-structure H∞ controller design using Augmented Lagrangian Particle Swarm Optimization with Fractional Order Velocity, Applied Soft Computing, 77, p. 688-695.##S. S, V. C. and H. S, A.,(2022), Nature inspired meta heuristic algorithms for optimization problems, Computing, 104(2), p. 251-269.##SHAMI, T. M., et al.,(2022), Particle Swarm Optimization: A Comprehensive Survey, IEEE Access, 10, p. 10031-10061.##GEN, M. and LIN, L., (2023), in Springer Handbook of Engineering Statistics, H. Pham Ed^Eds, Springer London, London, p. 635-674.##FIDANOVA, S., (2021), in Ant Colony Optimization and Applications, Ed^Eds, Springer International Publishing, Cham, p. 3-8.##HU, Z., et al.,(2024), Optimization of PID control parameters for marine dual-fuel engine using improved particle swarm algorithm, Scientific Reports, 14(1), p. 12681.##MOHD TUMARI, M. Z., AHMAD, M. A., SUID, M. H. and HAO, M. R.,(2023), An Improved Marine Predators Algorithm-Tuned Fractional-Order PID Controller for Automatic Voltage Regulator System, Fractal and Fractional, 7(7), p. 561.##FOSSEN, T. I.,(2021), Handbook of Marine Craft Hydrodynamics and Motion Control, Wiley.## ##

Vertical Double-Flap Wave Energy Converter: A Novel Concept to Capture Power from Ocean Wave 2 2 Wave Energy Converters (WECs) are devices designed to extract electricity from ocean waves. This study introduces a modular flap-type WEC in which a single flap is divided into two vertical segments. This modification aims to investigate its impact on power production. A dynamic model is developed for this dual-flap system, and the governing equations of motion of the system are derived. To account for the interaction between the flaps and the waves, hydrodynamic coefficients and excitation moments are computed using a Boundary Element Method (BEM), which takes the influence of wave-induced forces on each flap into consideration. The rotational motions of both flaps are then analyzed, with an assumption of regular waves. Furthermore, the power generated by each flap is calculated, based on their respective rotational responses. This analysis is aimed to evaluate the efficiency of the dual-flap configuration in harnessing wave energy. 55 65 2025/06/22025/08/192025/08/222025/06/42025/08/30 1404/6/8 2025/09/282025/10/82025/11/152026/01/42026/02/15 1404/11/26 Hamid Bab Hamid Bab Marine Engineering , School of Mechanical Engineering , Sharif University of Technology ایران hamid.bab@mech.sharif.edu Mahdi Aziminia Mahdi Aziminia Marine Engineering , School of Mechanical Engineering , Sharif University of Technology ایران mm_aziminia@mech.sharif.edu Abuzar Abazari Abuzar Abazari Associate Professor Marine Engineering , Chabahar Maritime University, Chabahar, Iran ایران abuzarabazari@cmu.ac.ir Mehdi Behzad Mehdi Behzad Professor Mechanical Engineering , School of Mechanical Engineering , Sharif University of Technology ایران m_behzad@sharif.edu Wave Energy Converter )WEC( vertical double flap power water wave Oscillating Wave Surge Converter (OWSC) IEA-OES, IEA-OES Annual Report, Technical Report, International Energy Agency - Ocean Energy Systems, 2007.##B. Czech and P. Bauer, "Wave energy converter concepts: Design challenges and classification," IEEE Industrial Electronics Magazine, vol. 6, no. 2, pp. 4-16, 2012.##A. Shafieefar and B. Kamranzad, "A Review of Tidal and Wave Energy in Southern Waters of Iran," Journal of Marine Science, vol. 2, no. 3, pp. 21-27, 2011.##A. F. de O. Falcão, "Wave energy utilization: A review of the technologies," Renewable and Sustainable Energy Reviews, vol. 14, no. 3, pp. 899-918, 2010.##W. L. Cummins, The impulse-response function and ship motions, Aeronautics and Astronautics, presented at the Symposium on Ship Theory, Institute für Schiffbau der Universität Hamburg, Hamburg, Germany, Jan. 25-27, 1962.##W. Sheng, E. Tapoglou, X. Ma, C. J. Taylor, R. Dorrell, D. R. Parsons, and G. Aggidis, "Time-domain implementation and analyses of multi-motion modes of floating structures," Journal of Marine Science and Engineering, vol. 10, no. 5, p. 662, 2022.##R. G. Dean and R. A. Dalrymple, Water Wave Mechanics for Engineers and Scientists. World Scientific, 1991.##E. Renzi and F. Dias, "Relations for a periodic array of flap-type wave energy converters," Applied Ocean Research, vol. 39, pp. 31-39, 2012.##The Oyster: World's first nearshore wave energy converter, London Research International, 2013.##E. Arbabi and A. Abazari, "The effects of dimension, geometry and the modules' orientation in a modular flap arrangement on the extracted power density of surge oscillating flap wave energy converter," Journal of Marine Engineering, vol. 14, pp. 14-25, 2020.##F. Kamal, A. Abazari, and R. Dorostkar, "The effect of flap dimension and wave angle on the dynamic response and extracted power of the hybrid system of offshore wind turbine and surge oscillating converter," Journal of Marine Engineering, vol. 20, no. 42, pp. 1-12, 2023.##Q. Li, J. Mi, X. Li, S. Chen, B. Jiang, and L. Zuo, "A self-floating oscillating surge wave energy converter," Applied Energy, vol. 257, p. 114031, 2020.##A. Abazari, & M.M Aziminia, (2022). Enhanced power extraction by splitting a single flap-type wave energy converter into a double configuration. Renewable Energy Research and Application (RERA), 4(2), 243-249.##M. Faizal, M. R. Ahmed, and Y.-H. Lee, "On utilizing the orbital motion in water waves to drive a Savonius rotor," Renewable Energy, vol. 34, no. 5, pp. 1084-1092, 2009.##Tan, Z. (2022). Investigation of the double pendulum small angle approximation model. World Scientific Research Journal, 8(11), 342-352.##Gomes, R. P. F., Lopes, M. F. P., Henriques, J. C. C., Gato, L. M. C., & Falcão, A. F. O. (2015). The dynamics and power extraction of bottom-hinged plate wave energy converters in regular and irregular waves. Ocean Engineering, 92, 922-934.##J. Falnes, Ocean Waves and Oscillating Systems: Linear Interactions Including Wave-Energy Extraction. Cambridge, UK: Cambridge University Press, 2002.##Abazari, A., and Aziminia, M. M., "Water wave power extraction by a floating surge oscillating WEC comprising hinged vertical and horizontal flaps," Journal of Energy Management and Technology, 2022.##He, C., Zhou, L., & Ma, X. (2023). Hydrodynamic response of a large-scale mariculture ship based on potential flow theory. Journal of Marine Science and Engineering, 11(10), 1995.##Renzi, E., & Dias, F. (2013). Hydrodynamics of the oscillating wave surge converter in the open ocean. European Journal of Mechanics - B/Fluids, 39, 1-11.##Raghavan, V., Lavidas, G., Metrikine, A., Mantadakis, N., & Loukogeorgaki, E. (2023). A comparative study on BEM solvers for wave energy converters. In Proceedings of the 2023 International Conference on Wave Energy (ICWE) (pp. 391-398). CRC Press.##M. Folley, T. W. T. Whittaker, and J. van't Hoff, "The design of small seabed-mounted bottom-hinged wave energy converters," in Proceedings of the 7th European Wave and Tidal Energy Conference (EWTEC), Porto, Portugal, 2007.## ##

Comparison of Metaheuristic Algorithms for Weight Optimization of a Semi-Submersible VAWT Substructure with Hexagonal Pontoons 2 2 In response to rising global energy demand and the urgent need to reduce greenhouse gas emissions, Offshore Wind Turbines (OWTs) have emerged as promising renewable energy solutions. Among deep-water support structures, semi-submersible platforms offer superior motion stability and design flexibility, but their high structural weight significantly affects construction and installation costs. This study compares five metaheuristic algorithms—Genetic Algorithm (GA), Ant Colony Optimization for Continuous Domains (ACOR), Artificial Bee Colony (ABC), Firefly Algorithm (FA), and Particle Swarm Optimization (PSO)—for weight optimization of a four-column semi-submersible substructure supporting a Vertical Axis Wind Turbine (VAWT) with hexagonal pontoons. The algorithms were first validated with a reference platform optimized using the Generalized Reduced Gradient (GRG) method. They were then applied to minimize the VAWT substructure weight by optimizing pontoon and column geometry, spacing, and draft under hydrostatic stability, motion, airgap, and feasibility constraints. Each algorithm was executed five times, and Kolmogorov–Smirnov tests confirmed normality of optimized weight and Number of Function Evaluations (NFE). Analysis of Variance (ANOVA) indicated statistically significant differences among algorithms, and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) was used for multi-criteria decision-making, considering average weight, NFE, accuracy, variance, and stability. Results indicate that ACOR achieved the highest rank, achieving ~37.6% (3690 tons) weight reduction. The findings demonstrate ACOR’s effectiveness as a decision-support tool for conceptual design of semi-submersible substructure of OWTs. However, it is expected that hydrodynamic loading, aero-structural coupling to be also considered for further detailed design. 66 79 2025/06/22025/08/192025/08/222025/06/42025/08/302026/01/14 1404/10/24 2025/09/282025/10/82025/11/152026/01/42026/02/152026/02/18 1404/11/29 Zanyar Delgarm Zanyar Delgarm Sahand Univ. of Tech. ایران zanyardelgarm@gmail.com Ahmad Reza Mostafa Gharebaghi Ahmad Reza Mostafa Gharebaghi Sahand University of Technology ایران mgharabaghi@sut.ac.ir Arefeh Emami Arefeh Emami Univ. of Hormozgan ایران emami@hormozgan.ac.ir Metaheuristic optimization Semi-submersible VAWT Statistical evaluation algorithm Hexagonal pontoons Multi-criteria decision Karimirad, M. (2014). Offshore energy structures: for wind power, wave energy and hybrid marine platforms. Springer.##Bilgili, M., & Alphan, H. (2022). 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