Sea Surface Wind Velocity Research Articles

Analysis of Marine Risers Subjected to Shoal/Deep Water in the Installation Process

Abstract The dynamics of the installation process of marine risers subjected to shoal/deep seawater is studied. The riser is assumed to be a cantilevered Euler‒Bernoulli beam. The upper end of the riser is clamped on the vessel or the drilling platform. The lower end of the riser is connected to the Blowout Preventer Stack (BOPs) and Lower Marine Risers Package (LMRP). The lateral fluid forces induced by the sea wave and sea current are introduced into the governing equations of motion. The lateral displacement and stress distributions of the riser are obtained by solving the governing equation of the riser via Galerkin’s discretisation scheme and a fourth-order Runge‒Kutta algorithm. The results indicate that the riser exhibits different behaviours under various depths because of the different distributions of the flow velocity ranging from the sea surface to the seabed. In the case of shoal water, the dynamics of the riser are dominated by the sea wave, while in the case of deep water it is affected mainly by the sea current velocity and sea surface wind velocity.

An Artificial Intelligence Method for the Prediction of Near- and Off-Shore Fish Catch Using Satellite and Numerical Model Data

The production of near- and off-shore fisheries in South Korea is decreasing due to rapid changes in the fishing environment, particularly including higher sea temperature in recent years. To improve the competitiveness of the fisheries, it is necessary to provide fish catch information that changes spatiotemporally according to the sea state. In this study, artificial intelligence models that predict the CPUE (catch per unit effort) of mackerel, anchovies, and squid (Todarodes pacificus), which are three major fish species in the nearand off-shore areas of South Korea, on a 15-km grid and daily basis were developed. The models were trained and validated using the sea surface temperature, rainfall, relative humidity, pressure, sea surface wind velocity, significant wave height, and salinity as input data, and the fish catch statistics of Suhyup (National Federation of Fisheries Cooperatives) as observed data. The 10-fold blind test results showed that the developed artificial intelligence models exhibited accuracy with a corresponding correlation coefficient of 0.86. It is expected that the fish catch models can be actually operated with high accuracy under various sea conditions if high-quality large-volume data are available.

Characterizing a Sea Turtle Developmental Habitat Using Landsat Observations of Surface-Pelagic Drift Communities in the Eastern Gulf of Mexico

Compared with our understanding of most aspects of sea turtle biology, knowledge of the surface-pelagic juvenile life stages remains limited. Young North Atlantic cheloniids (hard-shelled sea turtles) are closely associated with surface-pelagic drift communities (SPDCs), which are dominated by macroalgae of the genus Sargassum . We quantified SPDCs in the eastern Gulf of Mexico, a region that hosts four species of cheloniids during their surface-pelagic juvenile stage. Landsat satellite imagery was used to identify and measure the areal coverage of SPDCs in the eastern Gulf during 2003–2011 (1323 images). Although the SPDC coverage varied annually, seasonally, and spatially, SPDCs were present year-round, with an estimated mean area of SPDC in each Landsat image of 4.9 km2 (SD = 10.1). The area of SPDCs observed was inversely proportional to sea-surface wind velocity (Spearman's r = −0.33, p < 0.001). The SPDC coverage was greatest during 2005, 2009, and 2011 and least during 2004 and 2010, but the 2010 analysis was affected by the Deepwater Horizon oil spill, which occurred within the study region. In the eastern Gulf, the area of SPDC peaked during June–August of each year. Although the SPDC coverage appeared lower in the eastern Gulf than in other regions of the Gulf and the North Atlantic, surface-pelagic juvenile green, hawksbill, Kemp's ridley, and loggerhead turtles were found to be using this habitat, suggesting that eastern Gulf SPDCs provide developmental habitats that are critical to the recovery of four sea turtle species.

Mechanical behavior analysis for the determination of riser installation window in offshore drilling

The purpose of this paper is to figure out the safety operation window of riser in installation through taking three kinds of mechanical behavior. In this paper, the sea surface current velocity, surface wind velocity, wave height and wave period are taken as the evaluation factors of marine environment. The fleet angle at riser top section, the Mises equivalent stress on riser critical section, the axial dynamic load on riser bottom section and the riser transverse resonance are considered as the limiting factors which restrains the further complicacy of marine environment. Results show that the wave height and wave period mainly affect the lateral vibration frequency and the dynamic load. The sea surface wind velocity and sea surface current velocity determines the fleet angle and the Mises equivalent stress. However, compared with the fleet angle, the maximum equivalent stress is the main influence factor which limits the installation operation window. In general, under the circumstance of avoiding transverse resonance, smaller wave height and longer wave period are good for marine riser installation. The research has some reference value for safe and effective installation of marine riser.

Static analysis of deep-water marine riser subjected to both axial and lateral forces in its installation

In order to analyze riser stress and deformation in its installation, a static analysis model and equation have been established and the equation is solved by the finite difference method. In this model, the riser is regarded as a beam suspended in the floating drilling platform (ship) and subjected to both axial and lateral forces. In order to connect the Blowout Preventer Stack (BOPS) and the subsea wellhead, the floating drilling platform (ship) needs to move to drag the riser and BOPS. However, during the movement of floating drilling platform (ship), the riser stress distribution will change. The total stress variation with the movement speed of floating drilling platform (ship) has been figured out. Because riser deformation could be affected by several operational factors and environmental factors, the deformation variation with water depth, riser size, BOPS weight, sea surface wind velocity, sea surface tide velocity, wave height and wave period are discussed. Results show that there is a maximum movement speed of floating drilling platform (ship). If the actual speed is greater than the maximum value, the riser material will be in danger of damage. The riser deformation will increase as water depth, sea surface wind velocity and sea tide velocity increase and will decrease as riser size and BOPS weight increase. However, wave height and wave period almost have no impact on riser deformation. Since the analysis model established is a static one, the dynamic problem is not discussed in this paper.

Pairing of radar instruments on satellites could provide optimal mapping of sea surface winds

Scientists pairing two radar instruments with different sensitivities to ripples on the ocean surface may be able to measure the entire range of sea surface wind speeds—vital parameters that affect climate and the ocean environment.Ocean ripples detected via remote radar sensing are effective tracers of sea surface wind velocity [Woiceshyn et al., 1986; Wu, 1990b]. The scatterometer, which detects the scattering of radar waves by ripples on the sea surface, is deployed on Earth‐orbiting satellites to map wind velocities over the world' oceans. The scatterometer/wind anemometry relationship has been derived from data collected mainly under intermediate wind velocities.

Wind measurements from an array of oceanographic moorings and from F/S Meteor during JASIN 1978

During the Joint Air‐Sea Interaction (JASIN) experiment conducted in the northern Rockall Trough in the summer of 1978, oceanographic moorings with surface buoys carrying wind recorders were deployed in an array designed to investigate the variability of the near‐surface wind field at scales of from 2 to 200 km. The wind records together with observations taken on board the research vessels participating in JASIN have provided ground truth measurements for the sea surface wind velocity sensors on the Seasat satellite. During most of the experiment the wind field was characterized by spatial scales large in comparison with the separations between the buoys. On several occasions, spatial differences associated with cold fronts were identified, and it was possible to track the passage of the front through the array. However, quantitative analysis of the variability of the wind field was complicated both by a lack of data due to mechanical failures of some instruments and by significant differences in the performance of the diverse types of wind recorders. Reevaluation of the instruments used in JASIN and recent comparison of some of these instruments with more conventional sets of wind sensors confirm the possibility that there is significant error in the JASIN wind measurements made from the buoys. In particular, the vector‐averaging wind recorder on W2, which was one of the few instruments to recover a full length record and which was chosen during a Seasat‐JASIN workshop as the JASIN standard, had performance characteristics that were among the most difficult to explain.