Investigasi Resistance dan Seakeeping Kapal Trimaran dan Pentamaran Melalui Simulasi CFD dan Hasil EFD

Yuliora, Egi (2024) Investigasi Resistance dan Seakeeping Kapal Trimaran dan Pentamaran Melalui Simulasi CFD dan Hasil EFD. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Penggunaan kapal berlambung banyak (multihull) telah dilakukan selama 50 tahun terakhir. Kapal multihull memiliki keunggulan seperti area deck yang luas, hambatan yang lebih kecil pada kecepatan tinggi, dan stabilitas serta dinamika gerak kapal (seakeeping) yang lebih baik dibandingkan kapal berlambung tunggal (monohull). Namun, akurasi dalam memprediksi karakteristik hidrodinamika kapal, khususnya hambatan dan seakeeping, masih menjadi tantangan. Data hasil simulasi Computational Fluid Dynamics (CFD) dan Experimental Fluid Dynamics (EFD) di towing tank masih kurang memadai. Hambatan dan seakeeping multihull seperti trimaran dan pentamaran lebih kompleks dibandingkan katamaran, karena interaksi antara mainhull dan sidehull yang menyebabkan interferensi. Disertasi ini mengamati korelasi hambatan dan seakeeping dengan karakteristik seperti CP, CF, CW, CV, CVP, CT, dan IF serta RAO gerakan heave, roll, dan pitch pada sudut datang gelombang (μ) 0°, 45°, 90°, 135°, dan 180°. Simulasi CFD menggunakan FINETM/MARINE dari NUMECA untuk hambatan dan ANSYS AQWA untuk seakeeping, serta pengujian EFD di towing tank. Model trimaran (Tri) dan pentamaran (Penta) yang diuji adalah lambung NPL 4b transom-simetris dan variasi jarak separasi antara sidehull dan mainhull S/L = 0,2 (A), S/L = 0,3 (B), dan S/L = 0,4 (C), pada angka Froude Fr = 0,2 – 0,6. Hasil penelitian menunjukkan koefisien hambatan total (CT) trimaran 15,06% lebih kecil dibanding pentamaran, dan minimum pada Fr > 0,5. CT minimum trimaran pada model Tri-C sebesar 6,602 x 10⁻³, dan maksimum pada Tri-B sebesar 8,675 x 10⁻³, sedangkan pentamaran minimum pada Penta-C 7,377 x 10⁻³ dan maksimum pada Penta-D 1,067 x 10⁻2. Performa seakeeping untuk gerakan roll trimaran dan pentamaran sangat kecil dan dapat diabaikan. RAO heave dan pitch minimum dihasilkan oleh Tri-C dan Penta-B, dan maksimum pada Tri-A dan Penta-A. Selisih perhitungan dengan metode CFD dan EFD untuk hambatan total trimaran dan pentamaran masing-masing 6,07% dan 4,62%, sedangkan RAO heave trimaran dan pentamaran masing-masing 5,56% dan 5,96%. Hambatan dan seakeeping sering kali menjadi trade-off untuk performa terbaik. Namun, konfigurasi C dengan S/L 0,4 pada Tri-C dan Penta-C menunjukkan keunggulan dalam hambatan dan seakeeping terutama pada heading angle 135o. Hasil ini diharapkan dapat memperkuat database dalam mempresentasikan pengaruh hambatan dan seakeeping trimaran dan pentamaran, serta aplikasinya dalam penentuan tenaga penggerak dan kenyamanan kapal pada tahap desain awal.
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The utilization of multihull ships has been implemented for the past 50 years. Multihull vessels offer advantages such as larger deck areas, reduced resistance at high speeds, and improved stability and seakeeping compared to monohull vessels. However, accurately predicting the hydrodynamic characteristics of these vessels, particularly resistance and seakeeping, remains challenging. Data from Computational Fluid Dynamics (CFD) simulations and Experimental Fluid Dynamics (EFD) tests in towing tanks are still insufficient. The resistance and seakeeping of multihulls, such as trimarans and pentamarans, are more complex than catamarans due to the interaction between the main hull and side hulls, causing interference. This dissertation examines the correlation between resistance and seakeeping with characteristics such as CP, CF, CW, CV, CVP, CT, and IF, as well as the RAO of heave, roll, and pitch motions at wave encounter angles (μ) of 0°, 45°, 90°, 135°, and 180°. CFD simulations using FINETM/MARINE from NUMECA for resistance and ANSYS AQWA for seakeeping were conducted, along with EFD testing in a towing tank. The tested trimaran (Tri) and pentamaran (Penta) models featured NPL 4b transom-symmetric hulls and varied side hull separation distances relative to the main hull, with S/L ratios of 0.2 (A), 0.3 (B), and 0.4 (C), at Froude numbers (Fr) ranging from 0.2 to 0.6. Research findings indicate that the total resistance coefficient (CT) of the trimaran is 15.06% lower than that of the pentamaran, with minimum values at Fr > 0.5. The minimum CT for the trimaran model Tri-C is 6.602 x 10⁻³, and the maximum for Tri-B is 8.675 x 10⁻³, while the pentamaran's minimum CT for Penta-C is 7.377 x 10⁻³ and the maximum for Penta-D is 1.067 x 10⁻². The seakeeping performance for the roll motion of both trimarans and pentamarans is minimal and can be disregarded. The minimum RAO for heave and pitch is achieved by Tri-C and Penta-B, and the maximum by Tri-A and Penta-A. The discrepancy between CFD and EFD methods for total resistance calculations is 6.07% for trimarans and 4.62% for pentamarans, while the RAO heave discrepancy is 5.56% for trimarans and 5.96% for pentamarans. Resistance and seakeeping often involve trade-offs for optimal performance. However, configuration C with a length-to-beam ratio (S/L) of 0.4 in Tri-C and Penta-C exhibits advantages in resistance and seakeeping, particularly at a heading angle of 135 degrees. These findings are expected to enhance the database for presenting the effects of resistance and seakeeping in trimarans and pentamarans and their application in determining propulsion power and ship comfort during the preliminary design phase.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	CFD, EFD, hambatan, pentamaran, seakeeping, trimaran.
Subjects:	V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering > VM161 Ships--Hydrodynamics V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering > VM751 Resistance and propulsion of ships
Divisions:	Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38001-(S3) PhD Thesis
Depositing User:	Egi Yuliora
Date Deposited:	21 Aug 2024 03:52
Last Modified:	21 Aug 2024 03:52
URI:	http://repository.its.ac.id/id/eprint/115490

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