wave flume
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2022 ◽  
Vol 28 (3) ◽  
pp. 289-300
Author(s):  
Sujantoko Sujantoko ◽  
Eko Budi Djatmiko ◽  
Wisnu Wardhana ◽  
Aditya Hidayatullah

Floating breakwater merupakan solusi alternatif dari penggunaan fixed breakwater karena dapat digunakan secara efektif di daerah pesisir dengan kondisi tertentu, desain yang fleksibel untuk dikembangkan, dan instalasinya lebih mudah. Salah satu aspek dasar dalam desain floating breakwater adalah sistem mooring, karena digunakan untuk menjaga struktur tersebut tetap pada posisinya dan selain itu juga akan mempengaruhi kinerjanya. Penelitian ini bertujuan untuk mengetahui besarnya tegangan mooring maksimum pada tali mooring melalui model fisik. Penelitian dilakukan pada floating breakwater tipe gergaji dan  pontoon sebagai pembanding. Model floating breakwater dibuat dari bahan Polylactid Acid dan model tali mooring digunakan jenis polyethylene. Pengujian fisik dilakukan di laboraturium wave flume dengan gelombang irregular dan variasi tinggi gelombang (Hs), periode gelombang (T), elevasi muka air (d), dan sudut mooring (q). Hasil penelitian ini diperoleh nilai tegangan mooring maksimum pada floating breakwater tipe gergaji dan tipe pontoon pada sudut mooring 30⁰ dan elevasi muka air 45 cm secara berturut turut yaitu 5,278 N dan 4,913 N, sedangkan tegangan terkecil terjadi pada sudut mooring 60⁰ dan elevasi muka air 41 cm secara berturut turut yaitu 1,030 N dan 1,273 N. Pada perbandingan nilai tegangan mooring antara floating breakwater tipe gergaji pada sudut mooring (30o, 45o, 60o) adalah lebih besar 10.82%-19.71%, 24.00-40.94%, dan 22.2%-39.42% terhadap tipe pontoon pada elevasi muka air 41cm, 43cm dan 45cm secara berturut-turut


2021 ◽  
Vol 932 ◽  
Author(s):  
Amin Ghassemi ◽  
Saeid Zahedi ◽  
Leon Boegman

Abstract Breaking nonlinear internal waves (NLIWs) of depression on boundary slopes drives mixing in the coastal ocean. Of the different breaker types, fission is most commonly observed on mild slopes of continental margins. However, fission on mild slopes has rarely been investigated in the laboratory owing to limitations on flume length. In the present work, a train of NLIWs of depression is generated in an 18.2 m wave flume and shoaled upon a mild uniform slope. During fission, each NLIW of depression scatters into one or two NLIWs of elevation, which transforms into a bolus at the bolus birth point, where shear instability occurs through the pycnocline. The bolus propagates upslope, decreasing in size until it degenerates by shear and lobe-cleft instability, while losing volume to a return flow along the bed. The location of the bolus birth point, bolus propagation length scale, initial size and the number of boluses from each incident wave are parameterized from the wave half-width and the wave Froude number associated with the incident NLIW. These are compared with the characteristics of boluses generated by other breaking mechanisms on steeper slopes. Some bolus characteristics (height to length ratio, change in size and velocity field) are similar for boluses generated by fission, collapsing sinusoidal waves and internal solitary waves of elevation; however, the number of boluses, their birth point and initial height differ. The boluses formed by fission have more initial energy and no reflection. Further research is required to better quantify bolus-driven mixing on continental margins.


2021 ◽  
Vol 35 (6) ◽  
pp. 789-801
Author(s):  
Shu Li ◽  
Bin Teng

AbstractThe wave-induced fluid resonance between twin side-by-side rectangular barges coupled with the roll motion of the twin barges is investigated by both numerical simulation and physical model test. A 2D numerical wave flume, based on an open source computational fluid dynamics (CFD) package OpenFOAM, is applied for the numerical simulation. After numerical validations and convergent verifications, the characteristics of the fluid resonance in the gap between the twin rolling side-by-side barges are examined. The resonant frequency of the oscillating fluid in the gap between the twin rolling barges decreases compared with that between the twin fixed barges. Generally, the twin barges roll in the opposite directions, and their equilibrium positions lean oppositely with respect to the initial vertical direction. A physical model test is carried out for a further investigation, in which the twin barges are set oppositely leaning and fixed. From the present experimental results, a linear decrease of the resonant frequency with the increasing leaning angle is found. Combined with the numerical results, the deflection of the equilibrium positions of the twin barges is a relevant factor for the resonant frequency. Besides, the effects of the gap width and incident wave height on the fluid resonance coupled with roll motion are examined.


2021 ◽  
Vol 31 (1) ◽  
pp. 015006
Author(s):  
Gregorio Boccalero ◽  
Simon Chesne ◽  
Emmanuel Mignot ◽  
Nicolas Riviere ◽  
Claire Jean-Mistral

Abstract A novel concept of a surge wave energy converter for nearshore applications is investigated experimentally. The centimetre-sized prototype developed in this work represents a proof of concept of a submerged system, which entails a hybrid transduction solution for the electrical conversion of wave energy, that uses piezoelectric elements (PZEs) and dielectric elastomer generators (DEG). The idea is to exploit the horizontal pressure gradient and horizontal water velocity underneath the waves to compress the PZE and inflate each half wave period a soft variable capacitance, which composes the DEG. The electrical charges created by the PZE are used to polarize the DEG, which is able to multiply the input energy. This hybridization is conceived to allow the system to generate electrical energy from waves without conventional high voltage supplies, thus reducing production costs and allowing standalone clean electrical generation. The article provides the preliminary fluid-mechanical measurements performed in a wave flume with a first version of the prototype and supported by a model comprising the fluid/structure interaction, the materials response, and the electrical operations. An estimation of the output energy of a small-sized prototype in constant charge mode is computed, and perspectives for optimizing the system are presented.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jinah Kim ◽  
Taekyung Kim ◽  
Sang-Ho Oh ◽  
Kideok Do ◽  
Joon-Gyu Ryu ◽  
...  

AbstractAccurate water surface elevation estimation is essential for understanding nearshore processes, but it is still challenging due to limitations in measuring water level using in-situ acoustic sensors. This paper presents a vision-based water surface elevation estimation approach using multi-view datasets. Specifically, we propose a visual domain adaptation method to build a water level estimator in spite of a situation in which ocean wave height cannot be measured directly. We also implemented a semi-supervised approach to extract wave height information from long-term sequences of wave height observations with minimal supervision. We performed wave flume experiments in a hydraulic laboratory with two cameras with side and top viewpoints to validate the effectiveness of our approach. The performance of the proposed models were evaluated by comparing the estimated time series of water elevation with the ground-truth wave gauge data at three locations along the wave flume. The estimated time series were in good agreement within the averaged correlation coefficient of 0.98 and 0.90 on the measurement and 0.95 and 0.85 on the estimation for regular and irregular waves, respectively.


2021 ◽  
Vol 35 (5) ◽  
pp. 759-766
Author(s):  
Hong-qian Zhang ◽  
Ming-xiao Xie ◽  
Chi Zhang ◽  
Shao-wu Li ◽  
Hua-qing Zhang ◽  
...  

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 308
Author(s):  
Yuchen He ◽  
Pierre Suret ◽  
Amin Chabchoub

Coherent wave groups are not only characterized by the intrinsic shape of the wave packet, but also by the underlying phase evolution during the propagation. Exact deterministic formulations of hydrodynamic or electromagnetic coherent wave groups can be obtained by solving the nonlinear Schrödinger equation (NLSE). When considering the NLSE, there are two asymptotically equivalent formulations, which can be used to describe the wave dynamics: the time- or space-like NLSE. These differences have been theoretically elaborated upon in the 2016 work of Chabchoub and Grimshaw. In this paper, we address fundamental characteristic differences beyond the shape of wave envelope, which arise in the phase evolution. We use the Peregrine breather as a referenced wave envelope model, whose dynamics is created and tracked in a wave flume using two boundary conditions, namely as defined by the time- and space-like NLSE. It is shown that whichever of the two boundary conditions is used, the corresponding local shape of wave localization is very close and almost identical during the evolution; however, the respective local phase evolution is different. The phase dynamics follows the prediction from the respective NLSE framework adopted in each case.


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