Experimental investigation of bubble formation and motion mechanism near the moonpool

When a research ship sails at a high speed, there is relative motion between the ship and fluid. The ship is slammed by the fluid. To reduce the direct impact of the fluid, sonar is installed in the moonpool, and acoustic detection equipment is installed along the research ship bottom behind the moonpool. However, during high-speed sailing, a large number of bubbles form in the moonpool. Some bubbles escape from the moonpool and flow backward along the bottom of the ship. When a large number of bubbles are around the sonar and acoustic detection equipment, the equipment malfunctions. However, there have been few studies on bubble formation in the moonpool with sonar and distribution along the ship bottom behind the moonpool. Therefore, a related model was developed and prototype tests were carried out in this study. The appropriate similarity criteria were selected and verified to ensure the reliability of the experiment. Considering the influences of speed, sonar, moonpool shape, and draft, the reason and mechanism of bubble formation in a sonar moonpool were studied. An artificial ventilation method was used to simulate a real navigation environment. Because the bubbles are in a bright state under laser irradiation, the bubbles can be used as tracer particles. A high-speed camera captured illuminated bubbles. The distribution mechanism of bubbles along the ship bottom behind the moonpool was investigated using particle image velocimetry under the influence of the moonpool shape and sailing speed. The model experimental results agreed well with those of the prototype test. The air sucked into the water was the dominant factor in bubble formation in the moonpool. The bubbles were distributed in a W shape under the ship bottom.

Release of Gases in the Seas and Oceans

Over the recent decades, gas and oil fields have been intensively explored in the seas and oceans of the world. As part of the expedition of the Ukrainian research ship "Professor Vodyanitsky", gas flows from the bottom of the Black sea of the continental shoal located on the territory of Georgia were studied. In this article, we conducted an environmental study of the results obtained during the expedition. The analysis revealed the dangers that gas emissions found in this region may pose. The article presents map of the coastal shelf of Adjara with gas release points; Similar places of gas emissions on the black sea coast of Crimea are discussed; The results of gas extraction in the Caspian sea are presented; The nature of environmental changes caused by the removal of a layer of hydrogen sulfide from the sea depths to the upper layers of the sea during a gas eruption is analyzed.

RUF: Effective Sea Ice Floe Segmentation Using End-to-End RES-UNET-CRF with Dual Loss

Sea ice observations through satellite imaging have led to advancements in environmental research, ship navigation, and ice hazard forecasting in cold regions. Machine learning and, recently, deep learning techniques are being explored by various researchers to process vast amounts of Synthetic Aperture Radar (SAR) data for detecting potential hazards in navigational routes. Detection of hazards such as sea ice floes in Marginal Ice Zones (MIZs) is quite challenging as the floes are often embedded in a multiscale ice cover composed of ice filaments and eddies in addition to floes. This study proposes a segmentation model tailored for detecting ice floes in SAR images. The model exploits the advantages of both convolutional neural networks and convolutional conditional random field (Conv-CRF) in a combined manner. The residual UNET (RES-UNET) computes expressive features to generate coarse segmentation maps while the Conv-CRF exploits the spatial co-occurrence pairwise potentials along with the RES-UNET unary/segmentation maps to generate final predictions. The whole pipeline is trained end-to-end using a dual loss function. This dual loss function is composed of a weighted average of binary cross entropy and soft dice loss. The comparison of experimental results with the conventional segmentation networks such as UNET, DeepLabV3, and FCN-8 demonstrates the effectiveness of the proposed architecture.

Sea State Monitoring by Ship Motion Measurements Onboard a Research Ship in the Antarctic Waters

A parametric wave spectrum resembling procedure is applied to detect the sea state parameters, namely the wave peak period and significant wave height, based on the measurement and analysis of the heave and pitch motions of a vessel in a seaway, recorded by a smartphone located onboard the ship. The measurement system makes it possible to determine the heave and pitch acceleration spectra of the reference ship in the encounter frequency domain and, subsequently, the absolute sea spectra once the ship motion transfer functions are provided. The measurements have been carried out onboard the research ship “Laura Bassi”, during the oceanographic campaign in the Antarctic Ocean carried out in January and February 2020. The resembled sea spectra are compared with the weather forecast data, provided by the global-WAM (GWAM) model, in order to validate the sea spectrum resembling procedure.

Construction on Antarctica: Dismantling an existing wharf structure

<p>Rothera is the main mooring location in Antarctica for research vessels of the British Antarctic Survey (BAS). The existing wharf had reached the limit of its design life. To provide mooring of the new UK polar research ship, the RRS <i>Sir David Attenborough</i>, a larger wharf structure was designed that required removal of the existing structure. This paper describes the engineering and technical challenges on providing a safe and stable structure during dismantling as well as the effects of icebergs, low temperatures and wildlife around this Antarctic research station.</p>

Diversity and abundance of copepods on the north coast of Angola during hot season 2014-2016

The present work is aimed at discovering the diversity and abundance of copepods in the zooplankton community on the north coast of Angola, during the hot season 2014-2016. The samples were collected during the research cruise on board the Norwegian research ship “Dr. Fridtjof Nansen” in February - March on the Congo River and Luanda monitoring lines. Zooplankton sampling was performed using a multinet net in an oblique trawl (2014) and a WP2 net in a vertical trawl (2015 and 2016), both with 180 µm mesh. The samples were fixed in 4% formaldehyde and analyzed in the oceanography laboratory of the National Institute of Fisheries and Maritime Research in Angola. In the three years of sampling, copepods were present in the zooplankton community. The diversity of copepods on the northern Angolan coast, from 2014 to 2016 in the hot season, included 27 genera corresponding to 19 families. The Copepoda class was the most abundant group in the zooplankton community, corresponding to more than 80% of the abundance, having been represented by the orders Calanoida, Cyclopoida and Harpacticoida.

Oil Spats

This chapter presents a representative oil spat between Argentina and the United Kingdom. It recounts the 1976 incident, where an Argentine destroyer intercepted the RRS Shackleton, a British research ship, which the Argentines believed was unilaterally exploring for oil near the contested Falkland/Malvinas Islands. It narrates how the conflict between Argentina and the United Kingdom inspired an intensely hostile rhetoric but died down when the states began to pursue oil cooperation as a means of resolving their ongoing islands dispute. The chapter demonstrates how the next major conflict between Argentina and the United Kingdom, the Falklands War in 1982, was considered another red herring. It explains how the Falklands War was provoked by Argentine officials' determination to retake the islands before the sesquicentennial of British occupation.