scholarly journals Drifting dynamics of the bluebottle (<i>Physalia physalis</i>)

Ocean Science ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1341-1351
Author(s):  
Daniel Lee ◽  
Amandine Schaeffer ◽  
Sjoerd Groeskamp
Keyword(s):  
Linear Combination ◽  
Current Velocity ◽  
Equilibrium Condition ◽  
Shape Parameter ◽  
Numerical Models ◽  
Ocean Current ◽  
Common Occurrence ◽  
Aerodynamic Forces ◽  
Generalized Model ◽  
Physalia Physalis

Abstract. Physalia physalis, also called the bluebottle in Australia, is a colonial animal resembling a jellyfish that is well known to beachgoers for the painful stings delivered by its tentacles. Despite being a common occurrence, the origin of the bluebottle before reaching the coastline is not well understood, and neither is the way it drifts at the surface of the ocean. Previous studies used numerical models in combination with simple assumptions to calculate the drift of this species, excluding complex drifting dynamics. In this study, we provide a new parameterization for Lagrangian modelling of the bluebottle by considering the similarities between the bluebottle and a sailboat. This allows us to compute the hydrodynamic and aerodynamic forces acting on the bluebottle and use an equilibrium condition to create a generalized model for calculating the drifting speed and course of the bluebottle under any wind and ocean current conditions. The generalized model shows that the velocity of the bluebottle is a linear combination of the ocean current velocity and the wind velocity scaled by a coefficient (“shape parameter”) and multiplied by a rotation matrix. Adding assumptions to this generalized model allows us to retrieve models used in previous literature. We discuss the sensitivity of the model to different parameters (shape, angle of attack and sail camber) and explore different cases of wind and current conditions to provide new insights into the drifting dynamics of the bluebottle.

scholarly journals Drifting Dynamics of the Bluebottle

2021 ◽  
Author(s):  
Daniel Lee ◽  
Amandine Schaeffer ◽  
Sjoerd Groeskamp
Keyword(s):  
Linear Combination ◽  
Wind Velocity ◽  
Current Velocity ◽  
Equilibrium Condition ◽  
Shape Parameter ◽  
Numerical Models ◽  
Angle Of Attack ◽  
Ocean Current ◽  
Common Occurrence ◽  
Aerodynamic Forces

Abstract. Physalia physalis, also called the Bluebottle in Australia, is a colonial animal resembling a jellyfish that is well known to beachgoers for the painful stings delivered by their tentacles. Despite being a common occurrence, the origin of the Bluebottle before reaching the coastline is not well understood, and neither is the way it drifts at the surface of the ocean. Previous studies used numerical models in combination with simple assumptions to calculate the drift of this species, excluding complex drifting dynamics. In this study, we provide a new parametrization for Lagrangian modelling of the Bluebottle by considering the similarities between the Bluebottle and a sailboat. This allows us to compute the hydrodynamic and aerodynamic forces acting on the Bluebottle and use an equilibrium condition to create a generalised model for calculating the drifting speed and course of the Bluebottle under any wind and ocean current conditions. The generalised model shows that the velocity of the Bluebottle is a linear combination of the ocean current velocity and the wind velocity scaled by a coefficient ('shape parameter') and multiplied by a rotation matrix. Adding assumptions to this generalised model allows us to retrieve models used in previous literature. We discuss the sensitivity of the model to different parameters (shape, angle of attack and sail camber) and explore different cases of wind and current conditions to provide new insights into the drifting dynamics of the Bluebottle.

Hybrid Scaled Testing of a 5MW Floating Wind Turbine Using the SiL Method Compared With Numerical Models

2018 ◽  
Author(s):  
Felipe Vittori ◽  
Faisal Bouchotrouch ◽  
Frank Lemmer ◽  
José Azcona
Keyword(s):  
Wind Turbine ◽  
Numerical Models ◽  
Hydrodynamic Forces ◽  
Irregular Waves ◽  
Mooring Line ◽  
Global Dynamics ◽  
Aerodynamic Forces ◽  
Wave Tank ◽  
Aerodynamic Damping ◽  
Floating Wind Turbine

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.

Parameter Prediction Method for Submarine Cuttings Piles in Offshore Drilling

SPE Journal ◽  
2020 ◽  
Vol 25 (03) ◽  
pp. 1307-1332
Author(s):  
Baojiang Sun ◽  
Zhi Zhang ◽  
Zhiyuan Wang ◽  
Shaowei Pan ◽  
Ze Wang ◽  
...  
Keyword(s):  
Current Velocity ◽  
Geometric Characteristic ◽  
Stable State ◽  
Prediction Method ◽  
Continuous Model ◽  
Ocean Currents ◽  
Ocean Current ◽  
Offshore Drilling ◽  
Before And After ◽  
Drilling Site

Summary The cost of offshore drilling operations can be significantly reduced by discharging drilling cuttings into the seabed. However, this leads to accumulation of cuttings piles on the seabed near the drilling site. A certain thickness of cuttings piles changes the original trend of the seabed terrain undulation condition, thus bringing potential safety hazards to the underwater installation of production manifolds. Moreover, the interaction between cuttings and ocean currents near the cuttings piles causes the geometric shape of cuttings piles to evolve over time, which makes it more difficult to accurately predict their characteristics. On the basis of the force analysis of cuttings, considering the effects of cuttings properties (cutting size, density) and ocean-current velocity on the geometric characteristic evolution of the formed cuttings piles, a continuous model for describing the evolution of the returned cuttings piles is established in this study. This model can quantitatively characterize the functional relationship between characteristics of cuttings piles and relevant parameters (current velocity, cutting size, evolution time), and predict the location and geometry characteristics of the cuttings piles evolving into a stable state in ocean currents. Comparing the measured data in laboratory experiments and at an offshore drilling field, the relative error of the model amounts to less than 10%, which demonstrates its rationality. Simulation results show that there will be significant changes in the geometry of cuttings piles before and after the evolution, in which the intensity is correlated with current velocity and cuttings size, and cuttings piles might even split into several parts under certain conditions. The simulation and analysis of the transport and deposition of cuttings returned from the wellhead on the seabed is highly significant for the guide and optimal design of underwater production manifolds.

scholarly journals Ocean Renewable Energy Potential, Technology, and Deployments: A Case Study of Brazil

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3658 ◽  
Author(s):  
Milad Shadman ◽  
Corbiniano Silva ◽  
Daiane Faller ◽  
Zhijia Wu ◽  
Luiz de Freitas Assad ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Numerical Models ◽  
Salinity Gradient ◽  
Ocean Current ◽  
Brazilian Coast ◽  
Renewable Energy Resources ◽  
Energy Potential ◽  
Ocean Renewable Energy ◽  
Global Status

This study, firstly, provides an up-to-date global review of the potential, technologies, prototypes, installed capacities, and projects related to ocean renewable energy including wave, tidal, and thermal, and salinity gradient sources. Secondly, as a case study, we present a preliminary assessment of the wave, ocean current, and thermal gradient sources along the Brazilian coastline. The global status of the technological maturity of the projects, their different stages of development, and the current global installed capacity for different sources indicate the most promising technologies considering the trend of global interest. In Brazil, despite the extensive coastline and the fact that almost 82% of the Brazilian electricity matrix is renewable, ocean renewable energy resources are still unexplored. The results, using oceanographic fields produced by numerical models, show the significant potential of ocean thermal and wave energy sources in the northern and southern regions of the Brazilian coast, which could contribute as complementary supply sources in the national electricity matrix.

scholarly journals Kajian Pola Arus Laut dan Distribusi Sedimen Di Perairan Pantai Muara Kamal Jakarta Utara

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Permana Ari Soerjawo ◽  
Thonas Indra Maryanto
Keyword(s):  
Current Velocity ◽  
High Tide ◽  
Clay Fraction ◽  
Secondary Data ◽  
Acoustic Doppler Current Profiler ◽  
Google Earth ◽  
Ocean Current ◽  
Primary Data ◽  
Sediment Distribution ◽  
Current Profiler

ABSTRAKPola arus laut dan distribusi sedimen merupakan proses dinamika di suatu perairan yang mempunyai karakteristik berbeda-beda, sehingga berpengaruh terhadap pembentukan geomorfologi pantai di seluruh dunia. Penelitian ini bertujuan untuk mengetahui pola arus dan sedimen di perairan Pantai Muara Kamal Jakarta Utara di tahun 2012. Data yang digunakan merupakan data primer dan data sekunder, data primer meliputi data arus yang didapat dari pemasangan ADCP(Acoustic Doppler Current Profiler), data pasang surut dan sedimen perairan yang diambil dengan sedimen grab. Data sekunder berupa peta LPI (Lingkungan Pantai Indonesia) tahun 2000 skala 1:50.000 dari BIG (Badan Informasi Geospasial) dan citra satelit Google Earth tahun 2009. Hasil penelitian menunjukan bahwa kecepatan arus yang paling besar terdapat pada lapisan permukaan dengan kecepatan 0,242 m/s kearah barat daya (207,8o), kecepatan arus terkecil terdapat pada lapisan dasar yaitu 0,141 m/s kearah barat daya (207o). Hasil simulasi model hidrodinamika 2D, menunjukkan bahwa pada saat pasang arus laut mengarah ke daratan (selatan) dan pada saat surut arus laut mengarah ke laut lepas (barat laut). Berdasarkan kandungan ukuran butir sedimen di perairan Pantai Muara Kamal Jakarta Utara adalah pasir (64.98 - 72.15%) fraksi pasir tertinggi distasiun B(belakang geotekstil), lanau (24.56 - 29.36%) fraksi lanau tertinggi di stasiun C (depan geotekstil) dan Lempung (1.64 – 5.64%) fraksi lempung tertinggi di stasiun C (depan geotekstil). Kata kunci: Arus, Pantai Muara Kamal, Sedimen, model hidrodinamika 2D   ABSTRACTOcean current and sediment distribution are the dynamic process that have different charactheristic and therefore influenced beach geomorfophology around the world. This research aims to understand both ocean current and sediment pattern in Muara Kamal North Jakarta in 2012. This research used primary and secondary data, primary data were consisted of current data from ADCP (Acoustic Doppler Current Profiler), tidal data and bottom sediment samples. Secondary data involved of Indonesia Coastline Environmental map of year 2000 with scale 1:50.000 from Geospatial information Agency and a satellite data from Google earth of year 2009. The results showed that greatest ocean current velocity contained in the surface layer at a speed of 0,242 m/s with to southwest direction (207.8o), the smallest current velocity was in bottom layer is 0.141 m/s with southwest directiont (207o). Based on 2D hydrodynamic model simulation indicated that when high tide ocean current was flowed to the mainland (south) when low tide the current was flowed to the open sea direction. Based on the content grain size of the sediment, the studi area consisted of sand (64.98 - 72.15%) the highest sand fraction at station B(rare of geotextile) , silt (24.56 - 29.36%) the highest silt fraction at station C (front of geotextile) andclay (1.64 – 5.64%) the highest clay fraction at station C(front of geotextile) Key Words: Current, Muara Kamal Shoreline, Sediment, 2D hydrodynamics model

scholarly journals Modelling origin and transport fate of waste materials on the south-eastern Adriatic coast (Croatia)

2014 ◽  
Vol 11 (6) ◽  
pp. 2939-2969
Author(s):  
M. Tudor ◽  
I. Janeković
Keyword(s):  
Adriatic Sea ◽  
Flash Flood ◽  
Numerical Models ◽  
Remote Sensing Data ◽  
Water Levels ◽  
Waste Material ◽  
Ocean Current ◽  
The South ◽  
South Eastern ◽  
Adriatic Coast

Abstract. The south-eastern parts of the Adriatic Sea coastline were severely polluted by large amounts of accumulated waste material in the second half of November 2010. The waste, reported by major news agencies, accumulated dominantly during 21 November 2010 by favourable wind – ocean current transport system. In the study we analysed meteorological and oceanographic conditions that lead to the waste deposition using available in situ measurements, remote sensing data as well numerical models of the ocean and the atmosphere. The measured data reveal that an intensive rainfall event from 7 till 10 November 2010, over the parts of Montenegro and Albania, was followed by a substantial increase of the river water levels indicating flash floods that possibly splashed the waste material into a river and after to the Adriatic Sea. In order to test our hypothesis we set a number of numerical drifter experiments with trajectories initiated off the coast of Albania during the intensive rainfall events following their faith in space and time. One of the numerical drifter trajectory experiment resulted with drifters reached right position (south-eastern Adriatic coast) and time (exactly by the time the waste was observed) when initiated on 00:00 and 12:00 UTC of 10 November 2010 during the mentioned flash flood event.

Uncertainty Estimates for SeaSonde HF Radar Ocean Current Observations

2019 ◽  
Vol 36 (2) ◽  
pp. 231-247 ◽  
Author(s):  
Brian Emery ◽  
Libe Washburn
Keyword(s):  
Numerical Models ◽  
Surface Current ◽  
Ocean Modeling ◽  
Hf Radar ◽  
Ocean Current ◽  
Data Quality Control ◽  
Music Algorithm ◽  
Regional Ocean Modeling System ◽  
Mean Values ◽  
Uncertainty Estimates

Abstract HF radars typically produce maps of surface current velocities without estimates of the measurement uncertainties. Many users of HF radar data, including spill response and search and rescue operations, incorporate these observations into models and would thus benefit from quantified uncertainties. Using both simulations and coincident observations from the baseline between two operational SeaSonde HF radars, we demonstrate the utility of expressions for estimating the uncertainty in the direction obtained with the Multiple Signal Classification (MUSIC) algorithm. Simulations of radar backscatter using surface currents from the Regional Ocean Modeling System show a close correspondence between direction of arrival (DOA) errors and estimated uncertainties, with mean values of 15° at 10 dB, falling to less than 3° at 30 dB. Observations from two operational SeaSondes have average DOA uncertainties of 2.7° and 3.8°, with a fraction of the observations (10.5% and 7.1%, respectively) having uncertainties of &gt;10°. Using DOA uncertainties for data quality control improves time series comparison statistics between the two radars, with r2=0.6 increasing to r2=0.75 and RMS difference decreasing from 15 to 12 cm s−1. The analysis illustrates the major sources of error in oceanographic HF radars and suggests that the DOA uncertainties are suitable for assimilation into numerical models.

Resource Characterization and Statistical Modeling of Ocean Current at the Gulf Stream

2017 ◽  
Vol 51 (1) ◽  
pp. 52-63 ◽  
Author(s):  
Takuya Suzuki ◽  
Hassan Mahfuz ◽  
Marco Canino
Keyword(s):  
Current Velocity ◽  
Gulf Stream ◽  
Current Model ◽  
Ocean Current ◽  
Random Component ◽  
Mean Velocity ◽  
Gaussian Probability Density Function ◽  
Wide Range ◽  
Florida Straits ◽  
Predicted Values

AbstractWe developed a statistical ocean current model based on data collected from the Gulf Stream along the Florida Straits. Due to the random nature of ocean current velocity, the model was described by a Gaussian probability density function. Like wind speed distribution, the power spectral density (PSD) of ocean current velocity is distributed over a wide range of frequencies but characterized by distinguishable peaks resulting from tidal currents. Accordingly, the total velocity was considered as a sum of the mean velocity and a random component. To account for the tidal effect, a tidal current component was added based on PSD values. In addition, the model was formulated as a function of normalized depth that could be used at any site for resource characterization. For validation, the proposed model was used to predict mean velocity and standard deviation at four different sites along the Gulf Stream. Predicted values were then compared with measured data at those four locations, and a good correlation was observed.

Modelling the Microbial Carbon Pump in a changing ocean: current state and future directions

2020 ◽  
Author(s):  
Luca Polimene ◽  
Sevrine Sailley ◽  
Darren Clark ◽  
Susan Kimmance
Keyword(s):  
Numerical Models ◽  
Process Models ◽  
Bacterial Degradation ◽  
Ocean Current ◽  
Future Research ◽  
Adequate Model ◽  
Carbon Pump ◽  
Microbial Carbon ◽  
Microbial Carbon Pump ◽  
Residual Product

&lt;p&gt;Circa 624 gigatons of carbon are locked in the ocean as dissolved organic matter (DOM), an amount comparable with the entire CO&lt;sub&gt;2&lt;/sub&gt; content of the extant atmosphere. This DOM is operationally defined as refractory, meaning that it is resistant to bacterial degradation and persists in the ocean for millennia. Refractory DOM is considered primarily a residual product of heterotrophic bacterial activity after the bacterial consumption of more labile (i.e. easily degradable) DOM produced by marine autotrophs through photosynthesis. The process through which bacteria form refractory-DOM is termed the &amp;#8216;Microbial Carbon Pump&amp;#8217; (MCP). Abiotic degradation (e.g. photo-degradation) is thought to balance refractory DOM production, thus maintaining its current pool in steady state. However, recent studies suggest that changes in surface ocean inorganic nutrient availability, due to climate change related increases in thermal stratification, could modify MCP activity, increasing refractory-DOM production with respect to its consumption. Marine bacteria thus have the potential to mitigate increases in atmospheric CO&lt;sub&gt;2&lt;/sub&gt; by shunting more photosynthesised carbon into refractory-DOM. This hypothesis can only be tested by including the MCP in numerical models used for climate prediction. However, the lack of mechanistic understanding of the process (due, in turn, to the lack of experimental data) has hitherto prevented the development of adequate model formulations. In this talk, I will discuss the potential (and limitations) of existing process models to simulate (at least partially) the MCP and highlight future research directions (and related challenges) to develop new model formulations describing this process.&lt;/p&gt;

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