Papers by I Ketut Aria Pria Utama
IOP conference series, 2022
Ships are subject to increased surface roughness due to the attachment of biofoulings on their hu... more Ships are subject to increased surface roughness due to the attachment of biofoulings on their hull. When the surface of a ship’s hull is rough, increased frictional resistance can be expected. A ship’s frictional resistance make up almost 80 – 85% of its total resistance. Therefore, it is crucial to maintain the ship’s frictional resistance value to a minimum. In this study, the effects of roughness length scale due to biofouling on friction resistance are investigated. To achieve reliable results, this study used the 3D DTMB 5415 model that was established as a benchmark study by ITTC. Roughness length scales representing biofoulings are applied to the model and analyzed by using the CFD software at a service speed, reaching a Froude Number of 0.28. Results of the simulation are compared and analysed to gain an understanding of the increased friction resistance value due to biofouling. For the smooth case, the results are in agreement with the towing test conducted by ITTC. In addition, friction resistance is found to be increasing along with the rise of the roughness length scale.
Benchmark tests of FINETM/ Marine CFD code were performed to verify the ship-resistance calculati... more Benchmark tests of FINETM/ Marine CFD code were performed to verify the ship-resistance calculation results at high Froude numbers. The CFD code solves the Reynolds-averaged Navier-Stokes (RANS) equations with modelling of the free surface effects, that is, the generation of waves due to the ship movement on the water surface. A high-speed OSV boat was considered at three speeds (17, 20 and 26 knots), which correspond to the Froude numbers based on the volume of displacement FrV = 1.29, 1.52, and 1.98.The CFD results show a good agreement with the results of Savitsky’s formula and the numerical results obtained from Maxsurf Modeller. Further, a reasonable agreement was found between the CFD results and available experimental data. Flow visualisations show that the wave pattern behind the boat consists of transverse and divergent waves. As the boat’s speed increases, the wave height increases, and the wave pattern becomes more dominated by the divergent waves. These observations are consistent with the classical analytical predictions.
International Journal of Maritime Engineering, Dec 13, 2021
This report documents a large scale joint research project with the aim of improving the efficien... more This report documents a large scale joint research project with the aim of improving the efficiency of ship operations and management by providing a methodology and technology that can quantify the emission and fuel usage penalty due to bio-fouling on ship hull. This can be obtained through better understanding of turbulent boundary layer flows over rough surfaces that cause skin friction drag. Here six different institutions from four countries (Australia, Denmark, Indonesia, and UK) that consist of universities, a passenger ship company, a manufacturer of anti-fouling coatings, and the Indonesian Classification Society are formed. They represent three fields, namely: academic, industrial, and an independent party that supports policy makers. Each of them has different objectives and interests that are interconnected. The research collaboration uses an in-situ laser-based measurement technique of the water flow over the hull of an operating ship combined with under-water image-based surface scanning techniques. The shipboard experiments are accompanied by detailed laboratory experiments to provide further validation. This paper will discuss the importance and challenges of managing such collaboration and the significance of satisfying individual objectives from each three fields in order to achieve the overarching aim.
IOP conference series, May 1, 2023
A study into the effect of tip clearance on ducted propellers was carried out. Two series of prop... more A study into the effect of tip clearance on ducted propellers was carried out. Two series of propellers, namely B-series and Kaplan-series, were used. The gap between tip of propeller and ducted was varied from 2mm to 5mm. The study was conducted numerically using computational fluid dynamics (CFD) approach. The solver is based on the Reynolds-Averaged Navier-Stokes (RANS) solutions and two turbulence modelling, i.e. k-ω SST by Menter and explicit algebraic stress model (EASM), were applied in order to find out the optimum results. This paper objective to discuss energy efficiency on ships by investigating variations of propeller tip clearances. Overall results showed that EASM demonstrated better score (particularly in term of thrust and efficiency) than the k-ω SST. The highest thrust, torque and efficiency were achieved at 3mm tip clearance for both series. Moreover, Kaplan-series showed better results than the B-series propeller indicating that the use of ducted propeller using Kaplan-series is more appropriate.
The past decade has witnessed a rapid growth of interest in the development of fast catamaran for... more The past decade has witnessed a rapid growth of interest in the development of fast catamaran for various applications. The paper describes the study of interference resistance components on demihull separation. Catamarans or twin-hull vessels may be formed either by connecting two symmetrical demihulls or by splitting a mono hull into two halves to form two asymmetric demihulls. The slender body method in HullSpeed- Maxsurf Program was used for predicting the resistance components. The method assumes that the ship’s beam is small compared to its length. Effect of resistance interference components on catamaran hull separations are explained and discussed with some work from other published data, which shows good agreement.
Kapal, Oct 1, 2012
-Kapal katamaran adalah bentuk konfigurasi 2 lambung kapal atau memiliki 2 badan kapal. Bila diba... more -Kapal katamaran adalah bentuk konfigurasi 2 lambung kapal atau memiliki 2 badan kapal. Bila dibandingkan dengan kapal berbadan tunggal, banyak sekali kelebihan dari kapal katamaran ini yaitu stabilitas melintang yang lebih baik, hambatan yang nilainya kecil, dan area geladak yang lebih luas. Berbagai bentuk kapal kemudian dikembangkan untuk memenuhi kriteria desain kapal katamaran yang paling optimum salah satunya kapal katamaran flat side outside. Yaitu sebuah konfigurasi baru dengan lambung yang memiliki bidang datar atau asimetris diluar. Penelitian ini menjelaskan tentang pengaruh konfigurasi baru bentuk lambung katamaran asimetris flat side outside dengan variasi jarak pemisah lambung (S/L) yaitu S/L= 0.2; 0.3; dan 0.4 terhadap hambatan kapal katamaran asimetris. Analisa perhitungan hambatan dan pengaruh interferensi antara kedua lambung menggunakan CFD pada berbagai kecepatan dengan variasi angka Froude yaitu Fr = 0.19; 0.28; 0.37; 0.46; 0.55; dan 0.65. Hasil analisa menggunakan CFD kemudian dilakukan perbandingan dengan hasil pengujian katamaran asimetris pada Towing Tank -Laboratorium Hidrodinamika ITS. Hasil analisa menunjukkan pengaruh jarak pemisah lambung demihull terhadap komponen hambatan lambung katamaran asimetris flat side outside adalah signifikan walaupun tidak pada setiap variasi kecepatan. Kata Kunci-katamaran asimetris, jarak pemisah lambung, CFD.
Maneuverability kapal adalah kemampuan kapal berputar maupun berubah arah di semua kondisi perair... more Maneuverability kapal adalah kemampuan kapal berputar maupun berubah arah di semua kondisi perairan. Maneuverability ini penting dimiliki oleh sebuah kapal agar terhindar dari bahaya tabrakan terutama saat beroperasi di wilayah pelayaran terbatas. Maneuverability kapal secara teknis sangat dipengaruhi oleh ukuran utama, daun kemudi, dan sistem penggerak kapal. Tugas Akhir ini mencoba mengembangkan bentuk kemudi dengan tail flap yang sudah ada menjadi kemudi dengan dua flap tail yang bertujuan untuk memperbaiki salah satu jenis maneuverability kapal, yang dalam hal ini adalah turning ability. Daun kemudi dengan flap tail akan dimodifikasi menjadi kemudi dengan dua tail flap dengan tetap menjaga luasan permukaan nya dan kemudian dibandingkan kinerja kemudi ber- tail flap dengan kemudi konvensional. Berbagai variasi luasan flap yaitu yaitu perbandingan 40 : 30 : 30, 50 : 25 : 25 dan 50 : 30 : 20 terhadap luasan daun kemudi tersebut dilakukan untuk mencari bentuk daun kemudi dengan dua tail flap yang optimal dari sisi kemampuan gaya samping (side force). Perhitungan koefisien gaya samping daun kemudi ini akan menggunakan teknik CFD (Computational Fluid Dynamics). Model matematika gerakan manuver kapal dikembangkan berdasarkan persamaan linear dinamika kapal yang akan digunakan untuk menganalisa besarnya peningkatan maneuverability kapal yang menggunakan bentuk kemudi dengan dua tail flap terhadap penggunaan kemudi dengan satu flap tail dalam uji berputar (turning test).
DOAJ (DOAJ: Directory of Open Access Journals), 2017
-Perkembangan maritim tidak lepas dari kapal sebagai sarana transportasi. Hal itu menyebabkan keb... more -Perkembangan maritim tidak lepas dari kapal sebagai sarana transportasi. Hal itu menyebabkan kebutuhan akan dok sebagai tempat pembuatan dan reparasi kapal semakin meningkat. Semakin mahalnya harga lahan dan berbagai kelebihan yang ditawarkan membuat dok apung kian diminati sebagai solusi. Dok apung sendiri sebagai suatu struktur apung tidak lepas dari pengaruh gaya luar seperti gelombang, angin, dan arus. Tugas akhir ini bermaksud untuk melakukan analisis terhadap respon gerakan dok apung akibat gaya luar, tegangan yang terjadi pada rantai pengikatan, serta tingkat kenyamanan dari dok apung itu sendiri. Analisa dilakukan dengan pemodelan secara numerik menggunakan perangkat lunak Maxsurf dan Ansys Aqwa. Pada penelitian ini, dilakukan percobaan terhadap 3 kondisi dok apung yakni saat kosong, saat kapal naik dok, dan saat kondisi balas penuh, serta dengan 3 variasi sudut datang gelombang yakni 0⁰, 45⁰ dan 90⁰. Juga divariasikan konfigurasi pengikatan dok apung yakni menyilang dan menyebar. Setelah dilakukan analisis disimpulkan bahwa nilai tegangan rantai pada kondisi kosong dan kapal naik dok berada di bawah batas breaking load, sedangkan pada kondisi balas penuh tegangan yang terjadi melebihi batas breaking load baik pada desain pengikatan menyebar maupun pengikatan menyilang.Pengikatan menyilang memiliki nilai tegangan maksimum yang lebih besar dibandingkan dengan pengikatan menyebar. Tingkat ketidaknyamanan (Motion Sickness Incidence) gerakan dok apung adalah not uncomfortable atau dapat dikatakan nyaman dengan percepatan heave 0.208 m/s 2 . Serta gerakan dok apung yang masih memenuhi kriteria dari biro klasifikasi..
Peran transportasi laut sangatlah strategis karena merupakan fundamen (dasar) dari kehidupan ekon... more Peran transportasi laut sangatlah strategis karena merupakan fundamen (dasar) dari kehidupan ekonomi, termasuk dalam fungsinya sebagai sarana pengangkut batubara untuk memenuhi kebutuhan PLTU. Salah satunya yaitu PT. Indonesia Power Unit Bisnis Pembangkitan ...
Pada dasarnya hydrofoil yang tercelup penuh mempunyai kualitas kendali dan performansi kecepatan ... more Pada dasarnya hydrofoil yang tercelup penuh mempunyai kualitas kendali dan performansi kecepatan yang baik. Sistem kendali pada hydrofoil yang tercelup digunakan untuk untuk menstabilkan pergerakan dan meningkatkan stabilitas kapal. Tetapi Hydrofoil yang tercelup penuh ...
CFD Letters, May 6, 2024
Numerical analysis of fins effect on propeller performance was conducted, specifically using the ... more Numerical analysis of fins effect on propeller performance was conducted, specifically using the B4-70 and Ka4-70 propellers. The study investigated different types of fins, including bare fins and PBCF (Propeller Boss Cap Fins) using computational fluid dynamics (CFD) simulations. The explicit algebraic stress model (EASM) based on Reynolds-Averaged Navier-Stokes (RANS) equations and turbulence modeling was employed to determine the optimal results. The main objective of this research was to enhance energy efficiency in ships by examining various open propeller configurations. The CFD simulation results for open propellers B4-70 and Ka4-70, with the addition of boss cap fins, revealed interesting phenomena. When the open propellers B4-70 and Ka4-70 were equipped with PBCF, they would experience an increase in efficiency (η0). This was because the performance of the fins functioned optimally when the advance ratio (J) is high, as evident from the high velocity values. Thus, with higher velocity and lower pressure in the boss cap region at high J values, there was an elevation in thrust force due to the reduction of hub vortex. In the case of open propeller B4-70 with added PBCF, there was an increase in the efficiency value (η0) ranging from 3% to 5% when J varied from 0 to 0.7. Similarly, for propeller Ka4-70 with the addition of PBCF, there was an increase in the efficiency value (η0) ranging from 1% to 3% when J varied from 0 to 0.7. Notably, the use of an Energy-Saving Device (ESD) in the form of PBCF can increase the efficiency of ship propeller, as reported in this paper. Consequently, these findings affirmed the reliability of the overall calculations using the CFD approach.
CFD Letters, Nov 29, 2023
Unconventional system that are generally adopted for ship propulsion are Ducted Propellers. These... more Unconventional system that are generally adopted for ship propulsion are Ducted Propellers. These devices have recently been studied with medium-fidelity computational fluid dynamics code (based on the potential flow hypothesis) with promising results. Numerical and experimental comparison of ducted propeller with PBCF, case studies with Propeller Ka4-70 used combination ducted and PBCF Divergent. The study was done numerically using computational fluid dynamics (CFD) approach. The solver is based on the Reynolds-Averaged Navier-Stokes (RANS) solutions and turbulence modelling explicit algebraic stress model (EASM). The test data was obtained from CFD simulations consisting of the open propeller and combination Nozzle plus PBCF, but the experiment was done to Nozzle and PBCF only. All measurements were carried out from J = 0 to J = 1.0 with speeds from 0 m/s to 2.445 m/s. The results of the comparative investigation cases between numerical and experiment analysis from Ka4-70 propellers with Nozzle 19A and PBCF Divergent appears that between CFD and experiments, several phenomena are seen. (i) the Ka4-70 propeller without Nozzle 19A and PBCF divergent experienced large pressure at lowspeed J = 0.1 to high-speed J = 0.7, but Ka4-70 propeller with Nozzle and PBCF divergent reach highest pressure at J = 0.1 to J = 0.5; (ii) the Ka4-70 propeller without 19A nozzle and PBCF divergent increases the flow velocity at the boss cap fins but does not increase the axial induce velocity, while Ka4-70 propeller using nozzle and PBCF divergent increases the axial induce velocity of the blade, but does not increase the flow velocity of the boss cap fins; (iii) Ka4-70 propeller without Nozzle and PBCF value increase of propeller η 0 to 12% when ESD added in the form of Nozzle and PBCF when J is high, from J = 0.7 to J = 1.0. ; (iv) Ka4-70 propellers with Nozzle 19A and PBCF Divergent has very similar η 0 from J=0 to J=1.0. CFD approach are still appropriate to be relied upon for the overall simulation.
The Journal of Engineering, Apr 14, 2015
This paper discusses a correlation between non dimensional parameter of the ship (L/B,B/T, wake f... more This paper discusses a correlation between non dimensional parameter of the ship (L/B,B/T, wake fraction, ratio between induced and advance velocity, thrust loading coefficient) and energy gain by applying vane-turbine in the propeller slipstream. The data based on the basis of statistical data (numerical) and model testing. The correlation data can be calculated by quantifying the contribution of causal variables to a targeted effect variable directly and indirectly through other variables and this would be examined by Path analysis. By using this coefficient, it is possible to demonstrate which variable has the main contribution on the efficiency gain. The Data analysis of Microsoft Office Excel software is used to approach the calculation. It is found that L/B and CT affected indirectly the efficiency gain of vaneturbine.
The results of wind tunnel experiments on a pair of ellipsoids in close proximity are presented. ... more The results of wind tunnel experiments on a pair of ellipsoids in close proximity are presented. The experiments represented a reflex model of a multihull ship and investigated the components of viscous drag and viscous interaction effects between the hulls. The tests were carried out with and without turbulence transition strip at separation to length (S/L) raios of 0.27, 0.37, 0.47 and 0.57 and at Reynolds Number values up to 3.2 x 10 to the power of 6. Tests were included with a single-hull configuration with which the resistance characteristics of the twin-hull configuration could be compared. Results are presented for each S/L configuration as drag and sideforce coefficients at zero incidence. Surface pressure distributions over the hull were also obtained in order to provide a detailed knowledge of the distribution of forces over the hulls. The overall drag coefficients and pressure distributions were comparable with previously published data for single bodies of revolution in isolation. The results with two bodies demonstrated the existence of a viscous drag interaction between the bodies, and that this interaction is maintained at an approximately constant level up to about S/L = 0.5.
IOP conference series, Sep 1, 2022
Although the design of trimaran hull has gained popularity at the end of the 20th century, there ... more Although the design of trimaran hull has gained popularity at the end of the 20th century, there are few databases available to numerical analysis of trimaran hull. This paper presents a numerical study of the resistance of trimaran hull at various length ratio (S/L) 0.2, 0.3, 0.4 and Froude numbers 0.2 to 0.6 carried out by CFD simulation using FINETM/MARINE by NUMECA software and experimental data. Tri-A has a lower resistance than the trimaran B and C at low Froude number, but at hight Froude number 0.5 and 0.6, the Tri-A has a low resistance than the others. These results are compared with towing tank test data and obtained a lowest difference in the resistance of 0.98 % at TRI-A3. The lowest resistance for the trimaran model is Tri-C5 (Fr=0.6; S/L=0.4) with a total resistance coefficient (CT) of 65.89x10-4, this is due to favorable wave interference with a minimum IF of 0.02. The Interference Factor (IF) follows the same pattern in each configuration, however at maximum Fr, the minimal IF produced on Tri-A3(Fr=0.4; S/L=0.2), Tri-C4 (Fr=0.5; S/L=0.4), and Tri-C5 is 0.22, 0.12, and 0.02, respectively. Where the lowest IF indicates a positive effect because the resistance of the interference hull is lower hull at high speed. The results of this study are expected to be able to strengthen the data base in presenting the effect of interference resistance of the trimaran, which can then be applied directly in determining the magnitude of the ship’s propulsion at the preliminary design stage.
In this study it is aimed to investigate the application of ducktail at transom stern to reduce t... more In this study it is aimed to investigate the application of ducktail at transom stern to reduce total resistance using Computational Fluid Dynamics (CFD). Ducktail is additional retrofit device to reduce effect of wetted transom causes wave and wake which cannot fully generate far away therefore absorbs energy. The method about saving energy possibilities was determined. The RANSE code CFX fitted with shear stress transport (SST) turbulence is used to carry out the simulation. Grid generator ICEM CFD is used to build hybrid grids for RANS code solvers. The result indicate ducktail reduce resistance significantly based on Froude numbers. The wave and wake fully transmitted into the far field. Ducktail becomes alternative appendages to increase energy efficiency.
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Papers by I Ketut Aria Pria Utama