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An excessive trim by stern on a high-speed craft is vulnerable to decrease comfortable ride incorporated with the large pitch motion. To prevent such problem, the craft is then equipped with a device known as “trim-tabs” providing a lift force at the stern region, which leads to reduce pitch angle/trim of the craft. This paper presents computational modelling of trim-tabs on high-speed craft towards reducing the pitch motion in the calm water condition. Here, the commercial Computational Fluid Dynamic (CFD) software; called Numeca Fine Marine has been accordingly utilised to evaluate several effects of Froude numbers (Fr) and angle of the trim-tabs into characteristics of the lift force of the high-speed craft. The results revealed that the pitch motion of the high-speed craft equipped with the trim-tabs (5o) has significantly reduced up to 76% at Fr = 1.0. This can be explained that the installed trim-tabs has increased the negative trim moment, which inherently creates the restoring moment pushing the stern up along the pitch-axis. Meanwhile, this may cause involuntary the total ship’s resistance increased. In general, this simulation pointed out the advantage of the trim-tabs to increase the comfortability of the high-speed craft.

Predicting ship resistance in shallow water conditions is very important for the operational considerations of a ship. Shallow waters greatly affect viscous resistance, wave resistance and also propulsion efficiency. This study aims to determine the effect of water depth on the resistance of the ferry. The CFD method was used to simulate this phenomenon and its effects on the hull starting from the coefficient of ship resistance, surge force, sway force and yaw (hydrodynamic moment). Input speed at 9 – 13 knots with depth ratio H/T = 4 (deep water), H/T = 3 (deep water), H/T = 2 (medium water), H/T = 1.3 (shallow water), and H/T = 1 (very shallow water). The simulation results show a significant increase in total resistance, surge force, sway force, and hydrodynamic moment in shallow water conditions in every speed variation. This condition is caused by the increase in pressure received by the ship's hull when operating in shallow water.

The characteristics of the fore and aft foils at the various angles of attack incorporated with forward velocities have been vulnerable to induce strong nonlinearities to dynamic lift force and ship resistance. Then, a computational simulation is necessarily required to predict their performances in the calm water condition. This paper presents a computational investigation of the hydrofoil ship on predicting lift and ship’s resistance using fluid dynamic (CFD) simulation approach. Several parameters such as Froude numbers and the angle of attacks both of fore and aft foils have been accordingly taken into account. The results revealed that the subsequent increase on angle of attack of fore and aft foils was directly proportional to the lift force and the ship’s resistance. In addition, the lift force of the aft and fore foils with the angle of attacks of 10 degrees and 5 degrees, respectively, resulted in the significant increase of the lift force and the ship’s resistance. However, the subsequent increase of Froude number from 1.382 up to 1.626 has insignificant effect to the lift and the ship’s resistance of the hydrofoil. It can be concluded that CFD simulation is very beneficial to ensure an operational effectiveness of hydrofoil design towards prediction on the lift force and the hydrofoil’s resistance at the preliminary design stage.

Due to the increasing of fuel prices and volatile of environmental regulations, it is a challenge for Naval Architects to design a ship dealing with an optimum ship’s total resistance. The conventional design of catamaran hull has not satisfied yet to reduce the ship’s total resistance. This paper presents a numerical investigation into gaining sufficient reduction of the ship’s total resistance of catamaran through optimizing her hull form. To achieve this research objectives, a numerical optimization modelling coupled with a Computational Fluid Dynamics (CFD) approach has been successfully conducted. Several parameters such as length, beam and draft of catamaran hull have been taken into account towards reducing the ship’s total resistance. Here, the simulation constraints are applied to obtain the optimum dimension, where the length, beam and draft of the catamaran hull were optimized within the range of 1.2 m to 1.5 m, 0.11 m to 0.14 m and 0.07 m to 0.08 m, respectively. In general, the optimization simulation revealed that the optimum dimension of the catamaran hull resulted in reduction of the total ship’s resistance. The results showed that the optimum length, beam and draft of hull led to reduce by 21.08%, 16.95% and 17.91%, respectively. Merely, this numerical optimization simulation provides a useful way for reducing the total ship’s resistance of the catamaran at the preliminary design stage.

Desa Marabombang, Kecamatan Suppa, Kabupaten Pinrang merupakan sebuah desa yang berbatasan dengan selat Makassar. Karena lokasi geographis yang berbatasan dengan laut ini, maka sebagian penduduk Desa Marabombang berprofesi sebagai nelayan. Berbagai macam alat tangkap digunakan oleh masyarakat desa untuk mendapatkan ikan baik dengan menggunakan kapal maupun dengan bagan. Namun demikian, nelayan Desa Marabombang menghadapi kendala utama dalam melakukan aktivitasnya yakni semakin tingginya biaya bahan bakar atau energi. Untuk itu, pada program pengabdian yang akan dilakukan ini, masyarakat akan diperkenalkan dan dilatih untuk dapat memanfaatkan sistem hibrid genset dan energi matahari atau sistem photovoltaic. Kegiatan ini akan berlangsung selama sekitar 6 bulan mulai dari persiapan sampai penyusunan laporan dan publikasi. Kegiatan utama yang dilakukan pada program pengabdian ini adalah pelatihan dan penjelasan tentang komponen, cara pemakaian dan perawatan, serta hal lain yang berhubungan dengan sistem hibrid genset dan photovoltaic. Selain itu, untuk meningkatkan pemahaman masyarakat, maka kegiatan penjelasan ini akan diikuti dengan praktek langsung penggunaan sistem di bagan yang sudah ada. Dengan kegiatan pengabdian ini, maka diharapkan pemahaman masyarakat tentang penggunaan sistem hibrid genset dan photovoltaic dapat meningkat sehingga masyarakat dapat menggunakan sistem tersebut untuk meningkatkan produktivitas dan kesejahteraan terutama oleh nelayan bagan ikan di tempat pelaksanaan kegiatan ini.

Seiring dengan meningkatnya permintaan akan kapal kayu tradisional dengan ukuran besar hingga 400 GT dan panjang 50 m khususnya dalam mendukung kegiatan perikanan, transportasi barang dan penumpang antar pulau dan kapal wisata perairan. Hal ini menjadikan kemampuan olah gerak kapal kayu sangat penting, khususnya dalam perancangan daun kemudi. Pengabdian ini bertujuan untuk memberikan pelatihan dan keterampilan dalam penentuan dimensi dan desain daun kemudi kapal secara sederhana pada kelompok pengrajin kapal kayu di Desa Tanah Lemo Kecamatan Bontobahari Kabupaten Bulukumba. Metode yang dipergunakan dalam kegiatan pengabdian ini adalah applied theory sehubungan dengan penentuan dimensi daun kemudi sebagai peralatan kendali kapal. Kegiatan penyuluhan dan pelatihan ini telah dilangsungkan pada tanggal 19 September 2019 dengan hasil: i) Metode applied theory yang dipergunakan dalam pengabdian ini sangat cocok untuk meningkatkan skill para pengrajin kapal kayu tradisional; ii) Melalui pengukuran langsung dimensi luasan daun kemudi kapal kayu diperoleh hasil dengan perbedaan rata-rata sebesar 8,9% jika dibanding dengan mengunakan persamaan sederhana (pers. 1) dalam penentuan luasan daun kemudi sebagaimana persamaan yang umum digunakan dalam bidang teknik perkapalan.

A reliable prediction approach to obtain a sufficient thrust and torque to propel the ship at desired forward speed is obviously required. To achieve this objective, the authors propose to predict the thrust coefficient (KT), torque coefficient (KQ) and efficiency (η) of the propeller in open-water model test condition using Computational Fluid Dynamics (CFD) simulation approach. The computational simulation presented in the various number of rotational speed (RPM) within the range of advance ratio J=0.1 up to 1.05. The higher value of J lead to decrease 10KQ and KT. While the η increased steadily at the lower value of J and decreased at the higher value of J. The results also showed that the propeller with 1048 rpm obtain a better efficiency at J=0.95 with η= 88.25%, 10KQ=0.1654 and KT= 0.0942. The computation result is very useful as preliminary data for propeller performance characteristics.

Keselamatan merupakan priorotas utama dalam hukum pelayaran, maka perlu dirancang sedimikian rupa termasuk kebutuhan listrik untuk keadaan darurat/emergency di kapal. Dalam hal kelistrikan, sangat dibutuhkan sistem-sistem yang mendukung pengoprasian menyangkut peralatan apa saja yang harus beroperasi pada kondisi darurat/emergency di kapal. Perencanaan dan pemilihan kapasitas generator harus mampu memenuhi kebutuhan dan harus memperhatikan keefektifan daya generator yang dipilih karena akan berhubungan dengan masalah investasi atau harga yang dikeluarkan. Oleh karena itu, penelitian ini melakukan perhitungan ulang kapasitas generator dan juga melakukan perencanaan/penggambaran ulang diagram kelistrikan (wiring diagram) berdasarkan keadaan di lapangan dan dibandingkan dengan daya output dari generator untuk kondisi darurat/emergency. Dari penelitian ini, dapat dibuktikan secara teoritis bahwa perencanaan sistem kelistrikan di kapal dapat diterapkan secara nyata dan sesuai dengan ketentuan berlaku sehingga pada saat pemasangan instalasi listrik di kapal dan di masa yang akan datang dapat diandalkan demi kepuasan bagi pemilik kapal.

In order to compute the performance of a propeller blade using blade element momentum (BEM) method, the two- dimensional airfoil performance of the propeller blade in terms of lift and drag coefficients is necessary. Such data usually can be obtained from model experiment only for limited range of angle of attack (AoA). Therefore, it is necessary to extrapolate the limited experimental data to obtain the data for the whole range of AoA. The present study uses 2 (two) methods which are Viterna and Montgomerie methods in order to extrapolate the performance of an airfoil. The formulas and procedures of both methods are presented and their application are also demonstrated using an airfoil shape of NACA23012. From this study, a relatively good agreement of the airfoil performance in terms of lift and drag coefficients can be found from computation results of the both methods.

One of the most issues on a boat for using energy is resistance. Therefore some energy is needed to be able to overcome the boat resistance. The total resistance depends on the speed of the boat. By reducing the resistance, it will affect the energy usage on the boat. One way to reduce the boat resistance is by installing a stern flap to the stern. Stern flap is a new addition on the stern appendage. Previous studies, the stern flap was able to reduce the resistance. The reduction of resistance occurred on boats can reduce fuel consumption, so it can be one of the innovations in combating the energy crisis. This study used an experimental method that analyzes the position and size of the stern flap, where each position and size of the flap were tested at the same load. From the results and analysis, it shows that the changing position of the stern flap on the surface of the water will increase the boat speed by 4.62% and the changing size of the stern flap size to 85 × 80 cm will increase the speed of the boat by 3.82%.

Energy Procedia Vol. 65 tahun 2015 In order to optimally explore the Indonesian ocean wind energy using a mobile floating structure (MFS), the present carries out an investigation on ocean wind energy potential around Sulawesi and Maluku islands. The wind data used for analysis are from year 2008 collected by QuikScat satellite which used scatterometer to measure the wind speed above sea surface. Weibull distribution with two parameters is used to represent the characteristics of the wind model. Several methods are used to compute the parameters which are regression analysis (LRM), maximum likelihood method (MLM) and moment method (MM). The obtained parameters are used to compute the energy density of the sea areas around the islands. From this study, the sea areas which have the highest energy density every month could be determined. The areas are to be considered as the location of the MFS.

Hasil penelitian unggulan perguruan tinggi In order to optimally explore and utilize wind energy, an optimal design of wind turbine propeller blades needs to be obtained. Therefore, a computational method to analyze and optimize the performance of the blades needs to be developed. For that purpose, a computational method based on the Blade Element Momentum (BEM) theory is developed in the present study. In this method, the propeller blade is divided into several elements and it is assumed that there is no aerodynamic interaction amongst the elements. Furthermore, the equations from momentum and blade element theories are combined to obtain equations which are useful in blades design process. In the analysis, tip and root losses proposed by Prandtl are also implemented. The computation results are validated using Qblade software. A good agreement can be found from comparison of the results computed from the developed BEM and QBlade.

This research carried out an analysis on the use of high pressure flow behind propeller to cool the ship main engine known as Propeller Flow Cooling System (PFCS). The system is commonly found on relatively small fishing boats at South Sulawesi area of Indonesia. Using the system, the special pump for engine cooling purpose is not needed. The present research conducted an investigation on PFCS intake shape that would be optimal for delivering water to main engine which was arisen from the propeller rotation and to find the difference of water capacity produced from different shapes of intake. The implemented research methods were numerical and experimental methods that analysed the shape of two intake shapes namely, circular and elliptical shapes. In numerical computation, ANSYS CFX software was adopted. The result from numerical computations was an initial prediction to the tendency of the results. In order to verify the results, an experiment in a tank facility known as Circulating Water Channel (CWC) tank was conducted. In the experiment, measurements were performed at 2 (two) different locations which were at the center of propeller and at 0.7R of propeller blade. The results of the research found that the performance of the elliptical intake shape is more optimal compared to the circular one.

In order to harvest kinetic energy of a ship moving in waves, a permanent magnet linear generator is designed and simulated in the present study. For the sake of simplicity, only heave motion which will be considered in this preliminary study. The dimension of the generator is designed based on the dimension of the ship. Moreover, in order to designed an optimal design of rotor and stator, the average vertical displacement of heave motion is needed. For this purpose, a numerical method called New Strip Method (NSM) is employed to compute the motions of the ship. With NSM, the ship hull is divided into several strips and the hydrodynamics forces are computed on each strip. Moreover, because the ship is assumed to be slender, the total forces are obtained by integrating the force on each strip. After the motions can be determined, the optimal design of the generator is designed and simulated. The performance of the generator in terms of force, magnetic flux, losses, current and induced voltage which are the...

In order to avoid an excessive charging voltage which can damage power storage when converting wind energy using a turbine, it is necessary to control the charging voltage of the turbine generator. In the present study, a charging controller which uses an Arduino microcontroller, is designed. 3 (three) indicator lights are installed to indicate the battery charging process, power diversion to dummy load and battery power level. The performance of the designed controller is evaluated by simulating 3 cases. In this simulation, a battery with maximum voltage of 12.4 V is used. Case 1 is performed with input voltage equals the one set in Arduino which is 10 V. In this case, the battery is charged up to 10.8 V. In case 2, the input voltage is 13 V while the maximum voltage set in Arduino is also 13 V. In this case, the battery is charged up to maximum voltage of the battery. Moreover, the dummy load indicator is ON and charging indicator is OFF after the maximum charging voltage is reached because the electric...

In order to obtain accurate prediction of ocean wind energy, long term data are needed. However, one data sources might not able to provide long duration data. Therefore, the data need to be combined with other sources of data. However, before combining the data, it is important to compare and validate them to confirm their accuracy. In the present study, wind speed data collected by QuikScat and SSM/I (SSMIS) missions are compared and analyzed. QuikScat data were collected by a satellite with the same name, while Special Sensor Microwave Imager (SSM/I) and Special Sensor Microwave Imager Sounder (SSMIS) data are processed and offered by Remote Sensing System (RSS). SSM/I (SSMIS) are passive microwave radiometers carried onboard Defense Meteorological Satellite Program (DMSP). For the comparison, 5 (five) arbitrary positions over Sulawesi and Maluku islands sea areas are chosen for the analyses. For the evaluation purposes, beside time series of daily data from several chosen positions in research location, several statistical parameters are also computed and compared such as mean, standard deviation, root mean square (RMS), correlation coefficient.

In an attempt to obtain a 2D floating breakwater model with high performance in wave reflection, genetic algorithm (GA) was combined with boundary element method (BEM) in the previous study. The performance of the obtained model was verified with numerical relations as well as an experiment in towing tank. Moreover, its performance and characteristics in 3D case were also evaluated in the subsequent study. However, because the 3D model is formed by simply extruding the 2D shape in longitudinal direction, it only produces a model with uniform transversal shape which is considered to be less effective and efficient in terms of technical and economical points of view. Consequently, it is needed to modify the model to obtain a more realistic and efficient design without reducing significantly the high performance obtained previously. In the present study, several modifications of the original 3D model are performed which include placing moonpools inside the body. The performance and characteristics of the modified models in terms of wave elevations on the free surface are evaluated at various wavelengths by using higher order boundary element method (HOBEM). The accuracy of the computed results is confirmed with Haskind-Newman and energy conservation relations. From the modifications and evaluations of the models, it could be realized that the moonpools inside the body could be used to obtain a more realistic model without reducing the optimum performance of the original model shape.

The present study uses Quikscat data to assess the offshore wind energy potential at the Eastern part of Indonesia, around the Sulawesi and Maluku Islands. Weibull distribution with two parameters is used to represent the characteristics and distribution of the wind model. In order to confirm the accuracy of computations, statistical and numerical methods are used to compute the Weibull parameters which are regression analysis, maximum likelihood method and moment method. The obtained power density is used to draw monthly wind power maps for the sea areas around the islands. The maps are used to determine the most suitable location of a mobile conversion system every month. Moreover, by assuming that a NM72/2000 NEG Micon is installed, Monte Carlo Simulation is performed to determine the expected power percentage produced by the system every month.Copyright © 2015 by ASME

In the previous study, the optimal performance of a two-dimensional (2D) floating breakwater shape was obtained. The performance of this shape was also confirmed with a model experiment in a towing tank. Moreover, the shape’s performance in three dimensions (3D) was investigated in a subsequent study. However, to predict the shape’s performance in a real application more accurately, the shape’s characteristics in oblique waves must also be evaluated. In this study, the performance and characteristics of the model (hydrodynamic forces, body motions, wave elevations, and drift forces) are computed using a higher-orderboundary element method (HOBEM). The HOBEM, which is based on the potential flow theory and uses quadratic representation for quadrilateral panels and velocity potentials, can be used to obtain more accurate results with fewer panels compared to the conventional panel method (CPM). The computational accuracy is confirmed by using Haskind-Newman and energy conservation relations. In thisstudy, 3D wave effects were verified, and the body motions were much smaller compared to the 2D case. In addition, although the performance in terms of wave elevations depends on the measurement positions, the optimal performance obtained in the 2D case can be realized for a longer body length.&nbsp

Salah satu sarana yang dapat digunakan dalam perlindungan dan pengembangan daerah pantai dan pelabuhan adalah pemecah gelombang terapung. Pemecah gelombang terapung ini mempunyai banyak kelebihan dibandingkan pemecah gelombang yang statis atau diam. Namun demikian, pemecah gelombang tipe terapung ini pada umumnya mempunyai kemampuan untuk menghalangi gelombang datang yang masih rendah sehingga diperlukan sebuah penelitian untuk mendapatkan desain pemecah gelombang terapung dengan performa yang optimal. Pada penelitian sebelumnya, sebuah model 2D dengan performa yang optimal telah didapatkan. Model 2D ini didapatkan dengan menggunakan kombinasi metode panel langsung (direct panel method) dan algoritma genetika (genetic algorithm). Performa dan karakteristik model ini untuk kasus 3D telah pula dievaluasi secara numerik termasuk pada kondisi gelombang datang miring. Namun demikian, model 3D yang telah dievaluasi tersebut dapat dianggap tidak ekonomis dan efisien sehingga perlu untuk dimodifikasi untuk mendapatkan model yang lebih realistik dan efisien tanpa mengurangi secara signifikan performa optimal yang telah didapatkan sebelumnya. Untuk mendapatkan model yang lebih realistik dan efisien tersebut, model 3D yang telah didapatkan sebelumnya dijadikan sebagai model awal. Modifikasi terhadap model awal ini dilakukan berdasarkan variable presentase pengurangan material dan posisi perubahannya. Pada setiap modifikasi, performa dan karakteristik model akan dievaluasi menggunakan metode syarat batas orde tinggi atau higher order boundary element method (HOBEM). HOBEM membagi permukaan model menjadi sejumlah panel dan merepresentasikan panel-panel tersebut beserta dengan potensial kecepatan yang belum diketahui menggunakan variable kuadratic sehingga jumlah panel yang dibutuhkan jauh lebih sedikit untuk mendapatkan hasil yang lebih akurat dibanding dengan menggunakan metode panel langsung. Akurasi dan ketepatan perhitungan dapat dicek menggunakan relasi Haskind-Newman dan hukum konservasi energi. Dengan mengevaluasi pengaruh perubahan model terhadap karakter hidrodinamika dan performanya, akan dapat menjadi dasar untuk modifikasi selanjutnya sehingga sebuah desain optimal dari pemecah gelombang terapung dapat ditentukan. Setelah berbagai modifikasi, didapatkan sebuah model yang lebih realistik dengan membuat satu atau beberapa moonpool didalam model. Dengan menggunakan moonpool ini, energi gelombang dapat dikurangi akibat gerakan air didalam moonpool. Selain itu, penempatan moonpool didalam model dapat pula mengurangi jumlah material model secara signifikan sehingga biaya konstruksi pemecah gelombang ini akan menjadi lebih murah.