scholarly journals Studi Eksperimental Pengaruh Kecepatan Engkol dan Variasi Diameter Disk terhadap Amplitudo, Frekuensi dan Daya pada Mekanisme Pembangkit Gelombang

Author(s):  
Miftahul Ulum ◽  
Ardi Noerpamoengkas ◽  
Ahmad Anas Arifin ◽  
Hanif Darmawan Firmansyah
Keyword(s):  

Kebutuhan akan energi yang terbarukan di Indonesia perlu dikembangkan salah satunya adalah energi  yang berasal dari pembangkit listrik mikrohidro karena dapat meminimalisir penggunaan sumber energi yang berasal dari fosil. Penggunaan gelombang air sebagai seumber energi juga dirasa memiliki dampak resiko yang relatif kecil, serta pemanfaatannya yang mudah diperbarui. Pada penelitian ini akan dilakukan studi eksperimental dengan simulasi pada alat pembuat gelombang air. Studi eksperimental ini menggunakan metode variasi frekuensi kecepatan motor dan jarak engkol terhadap amplitudo dan frekuensi gelombang. Variabel bebas yang digunakan dalam penelitian ini adalah tinggi gelombang atau amplitudo dan panjang gelombang yang dihasilkan. Dengan membuat  prototype  wave  tank  dan  melakukan  pengukuran  dan  perbandingan antara parameter-parameter yang berpengaruh terhadap perhitungan gelombang air yaitu amplitude gelombang (A), periode gelombang (T), dan panjang gelombang (?), kecepatan putaran motor dan diameter poros engkol maka didapatkan parameter apa saja parameter yang saling berpengaruh serta bagaimana variasi kecepatan dan variasi poros engkol berpengaruh terhadap parameter-parameter yang ada. Sehingga dari penelitian ini didapatkan Frekuensi terbesar pada crank nomor 1 dengan kecepatan 120 rpm dengan frekuensi sebesar 2.83 Hz, amplitudo terbesar didapatkan pada crank nomor 3 kecepatan 1 dan 2 dengan amplitudo sebesar 30 mm, dan daya terbesar didapatkan pada crank nomor 3 kecepatan 1 dan 2 dengan energi bangkitan 4.41 watt

IEEE Access ◽  
2018 ◽  
Vol 6 ◽  
pp. 6585-6593 ◽  
Author(s):  
Xiaojie Tian ◽  
Qingyang Wang ◽  
Guijie Liu ◽  
Wei Deng ◽  
Zhiming Gao

Author(s):  
Hans Bihs ◽  
Mayilvahanan Alagan Chella ◽  
Arun Kamath ◽  
Øivind Asgeir Arntsen

For the stability of offshore structures, such as offshore wind foundations, extreme wave conditions need to be taken into account. Waves from extreme events are critical from the design perspective. In a numerical wave tank, extreme waves can be modeled using focused waves. Here, linear waves are generated from a wave spectrum. The wave crests of the generated waves coincide at a preselected location and time. Focused wave generation is implemented in the numerical wave tank module of REEF3D, which has been extensively and successfully tested for various wave hydrodynamics and wave–structure interaction problems in particular and for free surface flows in general. The open-source computational fluid dynamics (CFD) code REEF3D solves the three-dimensional Navier–Stokes equations on a staggered Cartesian grid. Higher order numerical schemes are used for time and spatial discretization. For the interface capturing, the level set method is selected. In order to test the generated waves, the time series of the free surface elevation are compared with experimental benchmark cases. The numerically simulated free surface elevation shows good agreement with experimental data. In further computations, the impact of the focused waves on a vertical circular cylinder is investigated. A breaking focused wave is simulated and the associated kinematics is investigated. Free surface flow features during the interaction of nonbreaking focused waves with a cylinder and during the breaking process of a focused wave are also investigated along with the numerically captured free surface.


1970 ◽  
Vol 42 (1) ◽  
pp. 111-123 ◽  
Author(s):  
J. F. A. Sleath

Measurements of the velocity distribution close to the bed have been made under laminar flow conditions in a wave tank. The classical solution for the velocity distribution was found to be valid when the bed was smooth, but considerable deviations between theory and experiment were observed with beds of sand. It is suggested that these deviations were caused by vortex formation around the grains of sand. The similarity between the velocity profiles obtained in these tests and those reported by other writers under supposedly turbulent conditions suggests that even at high Reynolds numbers vortex formation may continue to be the dominant effect in oscillatory boundary layers of this sort.


Author(s):  
Atsushi TAKAGI ◽  
Masashi WATANABE ◽  
Taro ARIKAWA

2018 ◽  
Vol 170 ◽  
pp. 89-99 ◽  
Author(s):  
Fábio M. Marques Machado ◽  
António M. Gameiro Lopes ◽  
Almerindo D. Ferreira

Author(s):  
Felipe Vittori ◽  
Faisal Bouchotrouch ◽  
Frank Lemmer ◽  
José Azcona

The design of floating wind turbines requires both, simulation tools and scaled testing methods, accurately integrating the different phenomena involved in the system dynamics, such as the aerodynamic and hydrodynamic forces, the mooring lines dynamics and the control strategies. In particular, one of the technical challenges when testing a scaled floating wind turbine in a wave tank is the proper integration of the rotor aerodynamic thrust. The scaling of the model based on the Froude number produces equivalent hydrodynamic forces, but out of scale aerodynamic forces at the rotor, because the Reynolds number, that governs the aerodynamic forces, is not kept constant. Several approaches have been taken to solve this conflict, like using a tuned drag disk or redesigning the scaled rotor to provide the correct scaled thrust at low Reynolds numbers. This work proposes a hybrid method for the integration of the aerodynamic thrust during the scaled tests. The work also explores the agreement between the experimental measurements and the simulation results through the calibration and improvement of the numerical models. CENER has developed a hybrid testing method that replaces the rotor by a ducted fan at the model tower top. The fan can introduce a variable force which represents the total wind thrust by the rotor. This load is obtained from an aerodynamic simulation that is performed in synchrony with the test and it is fed in real time with the displacements of the platform provided by the acquisition system. Thus, the simulation considers the displacements of the turbine within the wind field and the relative wind speed on the rotor, including the effect of the aerodynamic damping on the tests. The method has been called “Software-in-the-Loop” (SiL). The method has been applied on a test campaign at the Ecole Centrale de Nantes wave tank of the OC4 semisubmersible 5MW wind turbine, with a scale factor of 1/45. The experimental results have been compared with equivalent numerical simulations of the floating wind turbine using the integrated code FAST. Simple cases as only steady wind and free decays with constant wind showed a good agreement with computations, demonstrating that the SiL method is able to successfully introduce the rotor scaled thrust and the effect of the aerodynamic damping on the global dynamics. Cases with turbulent wind and irregular waves showed better agreement with the simulations when mooring line dynamics and second order effects were included in the numerical models.


2012 ◽  
Vol 117 (C11) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Chabchoub ◽  
N. P. Hoffmann ◽  
N. Akhmediev
Keyword(s):  

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