Underdeck Wave Slamming Model Tests for a Drilling Semi-Submersible Unit

2021 ◽  
Author(s):  
Lixin Xu ◽  
Xiaoqing Teng ◽  
Jinguang Wang ◽  
Sing-Kwan Lee ◽  
Jiancheng Liu ◽  
...  
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Impact Pressure ◽  
Wave Impact ◽  
Significant Wave ◽  
Wave Basin ◽  
Slamming Load ◽  
Wave Slamming ◽  
Order Of Magnitude ◽  
Vertical Impact

Abstract Negative air gap and wave slamming load on the deck box of drilling semi-submersible units in severe storm have received a great deal of attention, due to the COSL Innovator accident in 2015. Equally important is vertical slamming load on the MODU underdeck, which is less reported in the literature. The present paper attempts to derive characteristic vertical slamming pressure on the deck bottom, based on an extensive model test program for a drilling semi-submersible unit, CM-SD1000. A total of 96 3-hour wave impact tests were conducted including 4 sea states selected along the DNV steepness criterion curve in 3 wave headings. Two critical sea states were identified and each was tested with 16 random realizations in both the head and the beam waves. 8 force panels were installed on the under-deck to capture vertical wave impact events. It is found that the peak slamming pressures obtained can be fitted well with both Weibull and Gumbel probability function. The extreme vertical impact pressure predicted are of the same order of magnitude as the extreme horizontal impact pressure. The present study also shows that rise velocities of the wave surface relative to the deck bottom have a remarkable correlation with the wave slamming pressure in terms of probability distribution. The relative rise velocities can be properly derived from wave probe measurements. This offers an alternative approach to estimate the vertical impact pressure without resort to force panels. In contrast to horizontal wave slamming, the magnitude and frequency of vertical ones simply increases with significant wave height and wave steepness has much less effect. It is found that the extreme vertical impact pressure can be approximated well by a linear function of the significant wave height. The linear relationship, if validated by more tests, may help evaluate structural strength of the deck bottom before wave basin model testing.

Simulation of Wave Slamming on Open-Piled Structures Based on FLUENT

2012 ◽  
Vol 256-259 ◽  
pp. 1960-1964
Author(s):  
Feng Jin
Keyword(s):  
Experimental Data ◽  
Wave Height ◽  
Impact Pressure ◽  
Two Dimensional ◽  
Numerical Wave Tank ◽  
Regular Wave ◽  
Wave Impact ◽  
Wave Tank ◽  
Wave Slamming ◽  
Numerical Wave

In order to study the specialties of wave slamming on open-piled structures, a two-dimensional regular wave tank was established based on commercial CFD software FLUENT. Three typical cases of regular wave slamming on the open-piled structures were reproduced by using the numerical wave tank and compared with the experimental data available. Good agreements were obtained between the numerical and experimental results and the average of peak impact pressure was chosen as the characteristic impact pressure. Then regular wave impact pressure on the open-piled structures under various wave height, period and over height were simulated. The influences of the three parameters on the distribution of impact pressure were analyzed.

Physical and Numerical Investigations on Wave Run-Up and Dissipation under Breakwater with Fence Revetment

2021 ◽  
Vol 9 (12) ◽  
pp. 1355
Author(s):  
Enjin Zhao ◽  
Lin Mu ◽  
Zhaoyang Hu ◽  
Xinqiang Wang ◽  
Junkai Sun ◽  
...  
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Significant Wave Height ◽  
Irregular Waves ◽  
Structure Stability ◽  
Wave Impact ◽  
Significant Wave ◽  
Tide Level ◽  
Run Up ◽  
The Impact

Revetment elements and protective facilities on a breakwater can effectively weaken the impact of waves. In order to resist storm surges, there is a plan to build a breakwater on the northern shore of Meizhou Bay in Putian City, China. To better design it, considering different environmental conditions, physical and numerical experiments were carried out to accurately study the effects of the breakwater and its auxiliary structures on wave propagation. In the experiments, the influence of the wave type, initial water depth, and the structure of the fence plate are considered. The wave run-up and dissipation, the wave overtopping volume, and the structure stability are analyzed. The results indicate that the breakwater can effectively resist the wave impact, reduce the wave run-up and overtopping, and protect the rear buildings. In addition, under the same still water depth and significant wave height, the amount of overtopped water under regular waves is larger than that under irregular waves. With the increase of the still water depth and significant wave height, the overtopped water increases, which means that when the storm surge occurs, damage on the breakwater under the high tide level is greater than that under the low tide level. Besides, the fence plate can effectively dissipate energy and reduce the overtopping volume by generating eddy current in the cavity. Considering the stability and the energy dissipation capacity of the fence plate, it is suggested that a gap ratio of 50% is reasonable.

scholarly journals IMPLEMENTATION AND TESTING OF A POWER MATRIX-BASED WAVE ENERGY CONVERSION MODEL AND THE EFFECT SIMULATED ON THE WAVE FIELD — CASE STUDY OF LAGUNA, SC, BRAZIL

2019 ◽  
Vol 18 (1) ◽  
pp. 50
Author(s):  
P. H. Oleinik ◽  
W. C. Marques
Keyword(s):  
Energy Conversion ◽  
Wave Height ◽  
Wave Energy ◽  
Significant Wave Height ◽  
Renewable Energy Sources ◽  
Electrical Energy ◽  
Ocean Waves ◽  
Wave Energy Conversion ◽  
Significant Wave ◽  
Order Of Magnitude

Electrical energy has become an essential resource for mankind and, as the population and technological dependency grow, also does the electricity demand. This necessity boosted numerous studies which focus on clean and renewable energy sources. Ocean wave energy is one of the most environmentally friendly sources of energy since it does not emit pollutants to the atmosphere and does not produce harmful waste. Another positive point about ocean waves is that they are inexhaustible, therefore a power plant could, potentially, provide energy indefinitely. Hence the object of this study is to estimate the wave energy reduction caused by the presence of wave energy conversion (WEC) devices near the coastline of Laguna, Brazil. In order to study the coastal impact of a WEC farm, the third generation sea state model TOMAWAC was used to simulate the waves on the Southern Brazilian Shelf under two different conditions, with and without the presence of an array of WECs. The results show that the mean significant wave height in the blockaded area undergoes a slight drop, caused by the presence of the WECs, which do not appear in the other scenario. But this reduction of the significant wave height is negligible compared to the order of magnitude of the wave height itself.

On the Sensitivity of Passive Multistatic Radar Amplitude and Doppler Measurements to Significant Wave Height

2021 ◽  
pp. 1-5
Author(s):  
Jeffrey D. Ouellette ◽  
William T. Bounds ◽  
David J. Dowgiallo ◽  
Jakov V. Toporkov ◽  
Paul A. Hwang
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Significant Wave ◽  
Multistatic Radar

scholarly journals Estimation of Significant Wave Heights from ASCAT Scatterometer Data via Deep Learning Network

2021 ◽  
Vol 13 (2) ◽  
pp. 195
Author(s):  
He Wang ◽  
Jingsong Yang ◽  
Jianhua Zhu ◽  
Lin Ren ◽  
Yahao Liu ◽  
...  
Keyword(s):  
Deep Learning ◽  
Wave Height ◽  
Significant Wave Height ◽  
Incidence Angle ◽  
Ocean Waves ◽  
Global Scale ◽  
Learning Technology ◽  
Sea State ◽  
Significant Wave ◽  
Wave Heights

Sea state estimation from wide-swath and frequent-revisit scatterometers, which are providing ocean winds in the routine, is an attractive challenge. In this study, state-of-the-art deep learning technology is successfully adopted to develop an algorithm for deriving significant wave height from Advanced Scatterometer (ASCAT) aboard MetOp-A. By collocating three years (2016–2018) of ASCAT measurements and WaveWatch III sea state hindcasts at a global scale, huge amount data points (>8 million) were employed to train the multi-hidden-layer deep learning model, which has been established to map the inputs of thirteen sea state related ASCAT observables into the wave heights. The ASCAT significant wave height estimates were validated against hindcast dataset independent on training, showing good consistency in terms of root mean square error of 0.5 m under moderate sea condition (1.0–5.0 m). Additionally, reasonable agreement is also found between ASCAT derived wave heights and buoy observations from National Data Buoy Center for the proposed algorithm. Results are further discussed with respect to sea state maturity, radar incidence angle along with the limitations of the model. Our work demonstrates the capability of scatterometers for monitoring sea state, thus would advance the use of scatterometers, which were originally designed for winds, in studies of ocean waves.

scholarly journals Physical Modelling of the Effect on the Wave Field of the WaveCat Wave Energy Converter

2021 ◽  
Vol 9 (3) ◽  
pp. 309
Author(s):  
James Allen ◽  
Gregorio Iglesias ◽  
Deborah Greaves ◽  
Jon Miles
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Significant Wave Height ◽  
Wedge Angle ◽  
Wave Energy Converter ◽  
Wave Period ◽  
Surface Elevation ◽  
Energy Converter ◽  
Significant Wave ◽  
Model Scale

The WaveCat is a moored Wave Energy Converter design which uses wave overtopping discharge into a variable v-shaped hull, to generate electricity through low head turbines. Physical model tests of WaveCat WEC were carried out to determine the device reflection, transmission, absorption and capture coefficients based on selected wave conditions. The model scale was 1:30, with hulls of 3 m in length, 0.4 m in height and a freeboard of 0.2 m. Wave gauges monitored the surface elevation at discrete points around the experimental area, and level sensors and flowmeters recorded the amount of water captured and released by the model. Random waves of significant wave height between 0.03 m and 0.12 m and peak wave periods of 0.91 s to 2.37 s at model scale were tested. The wedge angle of the device was set to 60°. A reflection analysis was carried out using a revised three probe method and spectral analysis of the surface elevation to determine the incident, reflected and transmitted energy. The results show that the reflection coefficient is highest (0.79) at low significant wave height and low peak wave period, the transmission coefficient is highest (0.98) at low significant wave height and high peak wave period, and absorption coefficient is highest (0.78) when significant wave height is high and peak wave period is low. The model also shows the highest Capture Width Ratio (0.015) at wavelengths on the order of model length. The results have particular implications for wave energy conversion prediction potential using this design of device.

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