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Studi Numerik Pengaruh Geometri Dasar Laut Berbentuk Convex Terhadap Performa Hidrodinamis Oscillating Water Column (OWC) pada Gelombang Pendek Fadilah, Wahyu Nur; Junianto, Sony; Arini, Nu Rhahida; Pratilastiarso, Joke
ROTASI Vol 25, No 4 (2023): VOLUME 25, NOMOR 4, OKTOBER 2023
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.25.4.53-59

Abstract

Lautan yang luas menyimpan potensi energi yang besar dalam gelombang laut, menjadi solusi potensial terhadap krisis bahan bakar fosil. Wave Energy Converters (WECs) memegang peranan penting dalam mengoptimalkan potensi ini, dengan Oscillating Water Column (OWC) menjadi perangkat yang paling menjanjikan dan memiliki konstruksi yang sederhana. Penelitian ini mengeksplorasi kompleksitas hidrodinamis OWC, dengan fokus pada pengaruh profil dasar berbentuk convex terhadap efisiensi penangkapan energi, terutama dalam menghadapi gelombang laut yang tidak teratur dan alami. Simulasi numerik dua dimensi (2D) digunakan untuk menganalisis performa hidrodinamis OWC pada frekuensi rendah atau gelombang pendek. Keunikan penelitian ini terletak pada variasi lebar radius convex, dengan nilai yang diuji adalah 1; 1.5; 2; 2.5; 3; dan 3.5 meter. Analisa numerik menunjukkan terdapat penurunan performa hidrodinamis yang cukup signifikan ketika lebar radius bernilai lebih dari 2.5 meter. Hasil studi ini merekomendasikan bahwa untuk mendapatkan performa hidrodinamis yang optimal dan lebih baik dibandingkan dengan profil dasar berbentuk datar, lebar radius convex sebaiknya tidak bernilai lebih dari 75% dari kedalaman air.
Numerical Analysis of Wave Load Characteristics on Jack-Up Production Platform Structure Using Modified k-ω SST Turbulence Model Gilang Muhammad; Arini, Nu Rhahida; Ilman, Eko Charnius; Ariwibowo, Teguh Hady
EMITTER International Journal of Engineering Technology Vol 11 No 1 (2023)
Publisher : Politeknik Elektronika Negeri Surabaya (PENS)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24003/emitter.v11i1.806

Abstract

One of the important stages in the offshore structure design process is the evaluation of the marine hydrodynamic load in which the structure operates, this is to ensure an appropriate design and improve the safety of the structure. Therefore, accurate modeling of the marine environment is needed to produce good evaluation data, one of the methods that can accurately model the marine environment is through the Computational Fluid Dynamic (CFD) method. This research aims to analyze the ocean wave load of pressure and force characteristics on the jack-up production platform hull structure using the (CFD) method. The foam-extend 4.0 (the fork of the OpenFOAM) software with waveFoam solver is utilized to predict the free surface flow phenomena as its capability to predict with accurate results. The Reynold Averaged Navier Stokes (RANS) turbulence model of k-ω SST is applied to predict the turbulence effect in the flow field. Five variations of incident wave direction type are carried out to examine its effect on the pressure and force characteristics on the jack-up production platform hull. The wave model shows inaccurate results with the decrease in wave height caused by excessive turbulence in the water surface area. Excessive turbulence levels can be overcome by incorporating density variable and buoyancy terms based on the Standard Gradient Diffusion Hypothesis (SGDH) into the turbulent kinetic energy equation. The k-ω SST Buoyancy turbulence model shows accurate results when verified to predict wave run-up and horizontal force loads on monopile structures. Furthermore, test results of the wave load on the jack-up production platform hull structure shows that the most significant wave load is obtained in variations with the wave arrival direction relatively opposite to the platform wall. Especially in the direction of 90° because it also has the most expansive impact surface area. Meanwhile, the lower wave load is obtained in variations 45° and 135°, which have the relatively oblique direction of wave arrival to the surface.
Speed Comparation Between Two-wheeled Fuel and Electrically Converted Vehicle Using Simulation Abdussalam, Muhammad Zayyana; Arini, Nu Rhahida; Windarko, Novie Ayub
Jurnal Teknologi Elekterika Vol. 21 No. 2 (2024)
Publisher : Jurusan Teknik Elektro Politeknik Negeri Ujung Pandang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31963/elekterika.v21i2.5107

Abstract

Revo motorcycle conversion using 2 kW electric motor create slow two-wheeled electric vehicle which only reach 23,3 kph compared to it’s ICE propelled version which could reach 100 kph for equal space on chassis. Faster conversion based on Mio motorcycle using 3 kW BLDC motor resulting 75 kph maximum speed. A novel conversion kit based on Beat motorcycle using equal wattage BLDC motor claimed to be 90 kph which have some mechanism modification. To acquire similar comparison without many mechanism modification, simulation conducted using a pair of equally powered electric motorcycle model compared to it’s ICE motorcycle model. With the same 5.9 kW power rate and 250 kg mass resulting higher motorcycle top speed using ICE propulsion which is 61.959 kph, then the electrically converted motorcycle was 52.840 kph.
Thermal Performance Enhancement of Serpentine Cooling Design Using Branch Modification for Lithium-Ion Batteries Abrari, Arya Rafi; Ariwibowo, Teguh Hady; Pramadihanto, Dadet; Arini, Nu Rhahida; Binugroho, Eko Henfri; Miyara, Akio
Automotive Experiences Vol 7 No 3 (2024)
Publisher : Automotive Laboratory of Universitas Muhammadiyah Magelang in collaboration with Association of Indonesian Vocational Educators (AIVE)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31603/ae.12709

Abstract

Lithium iron phosphate (LiFePO4) batteries offer advantages such as low cost, safety, environmental compatibility, and stability over repeated cycles. However, when subjected to high currents, this battery generates thermal issues, particularly when arranged in packs. This study aims to maintain the LiFePO4 80Ah battery within an optimal temperature range (20 °C – 40 °C) while minimizing pumping power. The proposed research introduces a serpentine channel with additional branches. The design variations include a gradient in branch spacing and changes in channel width. Each design is evaluated using dimensionless parameters representing maximum temperature, temperature uniformity, pumping power, and cooling efficiency coefficient. The best design from each variation is then compared with the conventional serpentine (CS) channel design, which is well-known for its superior thermal performance. The gradient variation reduces ????????????????∗ and ???????? by 0.07 and by 0.42, respectively, compared to the non-gradient channel design, at a Re 400 and a C-rate 3 C. The design with the largest channel width reduces ????????????????∗ by 0.57 or 11.32 °C compared to the design with the smallest channel width. At a Re 1000 and C-rate 3 C, the reduction in ????????????????∗ for the proposed channel design compared to the CS design is 0.017. In terms of the friction factor (????), the proposed design is 0.0149 lower than the CS design. The results indicate that the thermal performance of the proposed channel design is better than that of the CS design, with reduced pumping power.
Simulasi Perbandingan Motor Listrik dengan Mesin Pembakaran Dalam Sebagai Penggerak Sepeda Motor CVT Abdussalam, Muhammad Zayyana; Arini, Nu Rhahida; Windarko, Novie Ayub
The Indonesian Journal of Computer Science Vol. 14 No. 1 (2025): The Indonesian Journal of Computer Science (IJCS)
Publisher : AI Society & STMIK Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33022/ijcs.v14i1.4425

Abstract

Fuel vehicle conversion to electric vehicle requires electric motor with power equivalently to the vehicle’s fuel engine. Some CVT motorcycle conversion experiment using BLDC motor propulsion resulting 40 km/hour maximum velocity electric vehicle. This study uses computer simulations to compare the performance of electric motor and gasoline fueled internal combustion engine. The results show that fuel vehicle performance overthrow electric vehicle where 200 kg total vehicle mass absorbing power about 4,9 kW for fuel vehicle and 2,8 kW for electric vehicle then 63 km/hour maximum velocity for fuel vehicle and 53 km/hour for electric vehicle. Those result become equal when both propulsion have equal input where absorbed power reach 2,7 kW and maximum velocity reach 50 km/hour.
Modifikasi Sudut Masuk Impeller Pompa Sentrifugal Untuk Mengurangi Efek Kavitasi Arini, Nu Rhahida; Ramadhani, Desy; Diana, Lohdy; Reivanda, Reihan Rizky
Journal of Applied Civil Engineering and Infrastructure Technology Vol 6 No 1 (2025): Agustus 2025
Publisher : Indonesian Society of Applied Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.52158/jaceit.v6i1.984

Abstract

A centrifugal pump utilizes pressure energy, which is generated by the kinetic energy of involute impeller rotation. A common issue in pump operation is cavitation, a physical phenomenon that occurs when the static pressure of the fluid drops below its saturation pressure, causing the fluid to boil. This phenomenon affects the pump, leading to problems such as shockwaves and erosion, which must be minimized. This research aimed to investigate the influence of pump impeller modifications in reducing the cavitation effect using the computational fluid dynamics (CFD) method. The modifications focused on adjusting the inlet and outlet angles of the pump impeller. A 3D CFD model was developed using OpenFOAM, a CFD software tool, and the cavitation number (Ca) was used as the primary parameter to measure cavitation levels. Additionally, Ca was compared to a reference cavitation number, calculated based on the saturated pressure, while cavitation points at the impeller inlet and outlet were visualized using Paraview software. The results showed that a pump impeller with a blade inlet angle (β₁) of 21,69° resulted in 39.157 cavitation points, whereas modifying β₁ to 38,66° reduced the cavitation points to 32.778, thus decreasing the cavitation points by 6.379. This confirmed that modifying β₁ significantly reduces the cavitation effect.
The Experimental Study of the Lens Wind Turbine Performance with Vortex Generator Diana, Lohdy; Pratilastiarso, Joke; Safitra, Arrad Ghani; Arini, Nu Rhahida; Saputra, Firman Yunan; Syahputra, Ar Rayyan Ikhsan; Putra, Firdaus Fhudoli
invotek Vol 24 No 3 (2024): INVOTEK: Jurnal Inovasi Vokasional dan Teknologi
Publisher : Universitas Negeri Padang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/invotek.v24i3.1237

Abstract

Wind energy potential is available in several regions in Indonesia with wind ranges reaching 5 m/s. Wind turbine research continues to develop to produce optimal power. The aim of this research is to determine the performance of wind turbines equipped with diffusers or lens that put triangle fin vortex generator on lens’s surface. The turbine blade used Clark-Y that has a winglet angle of 45-degrees. There are three variations of lens wind turbine that were tested: without vortex generator, z/h=4.5, z/h=2.5, z/h=0.5. The research was carried out experimentally with fifth wind velocity 3 m/s, 3.5 m/s, 4 m/s, 4.5 m/s, and 5 m/s. The results analyzed to determine turbine performance are turbine rotation, the power produced due to wind direction. Based on the results of the experiments that have been carried out, the results were obtained a straight comparison between TSR and wind turbine rotation (rpm), and straight comparison between Cp and TRS. The Cp is largest in a lens wind turbine with a vortex generator z/h=0.5, which is 0.59 and has the highest power output of 473 watt.
Rancang Bangun Alat Ukur Potensi Gelombang Laut Dengan Metode Superposisi Gelombang Kahfi, Ahmad Khairul; Arini, Nu Rhahida; Sesulihatien, Wahjoe Tjatur
Jurnal Kelautan Vol 18, No 2: Agustus (2025)
Publisher : Department of Marine Sciences, Trunojoyo University of Madura, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21107/jk.v18i2.30124

Abstract

ABSTRACTBanyak perangkat maritim, seperti sistem navigasi kapal dan Pembangkit Listrik Tenaga Gelombang Laut (PLTGL), sangat bergantung pada data karakteristik gelombang laut. Beberapa alat ukur karakteristik gelombang laut telah dijual di pasaran, namun tidak terjangkau dan sulit dioperasikan. Penelitian ini bertujuan untuk merancang dan membangun alat ukur ketinggian gelombang laut berbasis pengolahan sinyal menggunakan metode Fast Fourier Transform (FFT) dan prinsip superposisi. Sistem pengukuran menggunakan sensor Inertial Measurement Unit (IMU) yang merekam data percepatan secara real-time. Data tersebut kemudian dianalisis untuk mengekstrak parameter utama gelombang, termasuk tinggi gelombang, frekuensi, dan kecepatan rambat gelombang. Eksperimen dilakukan di fasilitas wave generator selama 5 menit dengan frekuensi pengambilan data sebesar 25 Hz. Hasil eksperimen menunjukkan kondisi gelombang uji pada frekuensi motor 25 Hz mempunyai tinggi gelombang air sebesar 1 cm. Hasil pengukuran dibandingkan dengan pengukuruan/pengamatan visual di kolom wave generator menunjukkan perbedaan pengukuran sebesar 2% dengan frekuensi dominan yang didapatkan berada di 3,2 Hz yang didapatkan dari amplitudo dominan di sinyal domain waktu. Studi ini diharapkan dapat berkontribusi dalam perkembangan teknologi maritim dalam mendukung sektor pelayaran dan energi terbarukan berbasis kelautan di Indonesia.Kata Kunci: Ketinggian Gelombang, FFT, Gelombang Superposisi, Karakteristik Gelombang, Sensor IMU.ABSTRAKMany maritime devices, such as ship navigation systems and Wave Ocean Power Plants, rely heavily on data on ocean wave characteristics. Several water wave characteristic measuring instruments have been sold on the market, but not affordable and difficult to operate. The aim of this study is to design and build a wave height measuring instrument based on signal processing using the Fast Fourier Transform (FFT) method and the superposition wave. The measurement system uses an Inertial Measurement Unit (IMU) sensor that records acceleration data in real time. The data is analyzed to extract the main parameters of the wave, including wave height, frequency, and wave propagation speed. The experiment is conducted at the wave generator facility for 5 minutes with a data collection frequency of 25 Hz. The results of the experiment show that the test wave conditions at a motor frequency of 25 Hz had a water wave height of 1 cm. The measurement results compared with the visual measurement/observation in the wave generator column show a measurement difference of 2%, with the dominant frequency obtained being 3.2 Hz, derived from the dominant amplitude in the time domain signal. This study is expected to contribute to the development of maritime technology in supporting the shipping and marine-based renewable energy sectors in Indonesia.Keywords: FFT, IMU Sensor, Superposition Wave, Wave Characteristic, Wave Height
Numerical study of non-linear twisted blades for tidal turbines improvement Arini, Nu Rhahida; Atmojo, Philips Ade Putera; Saputra, Deni; Satrio, Dendy
International Journal of Advances in Applied Sciences Vol 14, No 3: September 2025
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijaas.v14.i3.pp894-906

Abstract

Despite the growing demand for renewable energy, the utilization of tidal energy remains underdeveloped due to efficiency limitations in turbine design. Addressing this gap, this study investigates the performance of horizontal-axis tidal turbines (HATT) by comparing two foil designs, National Advisory Committee for Aeronautics (NACA) 2415 and OptA, to optimize energy extraction efficiency. The research employs computational fluid dynamics (CFD) simulations using OpenFOAM to evaluate the effects of foil modifications and non-linear twist distributions on turbine performance across varying tip speed ratios (TSR). The results indicate that the OptA foil significantly improves turbine performance, achieving a 41.4% increase in torque and a 40.2% increase in power coefficient (CP) at TSR 5, which was identified as the optimal operating condition. The OptA foil enhances velocity distribution, reduces flow separation, and improves vortex behavior, leading to greater efficiency and stability. These findings confirm that foil selection and blade design modifications play a critical role in HATT optimization.
Participatory Design in Developing Gamification on Introducing Renewable Energy to Teenage Students Burhan, Rifaatul Mahmudah; Rante, Hestiasari; Arini, Nu Rhahida; Hasnaoui, Abir
The Indonesian Journal of Computer Science Vol. 10 No. 2 (2021): The Indonesian Journal of Computer Science
Publisher : AI Society & STMIK Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33022/ijcs.v10i2.3002

Abstract

The Covid-19 pandemic has had an impact on all sectors, including the world of education. Learning that has been done using traditional methods such as books has turned to virtual media such as zoom, google meet, and social media. This makes students less interested and feel bored. In addition, the current use of energy sources continues to increase which results in the depletion of energy sources. this is due to a lack of knowledge and awareness regarding renewable energy and energy sources. In this study, we used a participatory design method that involved teachers and students in collecting data that was relevant to everyday life. We also conducted interviews and asked students and teachers about their study habits and the meaning of renewable energy and their daily life related to energy, the impressions they have of attending classes, and any opinions for further improvement.This method is proven to help provide outstanding results in decision-making to build gamification applications as learning media that can attract interest and motivation to learn for students, especially junior high school students. As a result of the analysis of students' understanding and concern about renewable energy, it was analyzed as "enough" with a percentage of 57.1%. Based on the results of research and student opinions, we would like to suggest that there must be the development of learning methods or alternative media such as gamification for junior high school students.