scholarly journals Capacity Estimation of the Very Short-Range Electromagnetic Underwater Channel Based on Measurements

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Jesús López-Fernández ◽  
Unai Fernández-Plazaola ◽  
Jose F. Paris
Keyword(s):  
Acoustic Waves ◽  
Electromagnetic Waves ◽  
Short Range ◽  
Oil And Gas ◽  
Sea Water ◽  
Water Movement ◽  
Propagation Speed ◽  
Ergodic Capacity ◽  
Transmitter Power ◽  
Offshore Oil And Gas

The significant attenuation experienced by electromagnetic waves in sea water is the main reason why acoustic waves are generally preferred in underwater communication. Nevertheless, acoustic waves have various drawbacks. For example, they are negatively affected by factors such as mechanical noise, slow propagation speed, and, particularly, low bandwidth, which leads to digital links at a lower bit rate. However, in short-range links, these problems can be overcome by reconsidering the use of electric current communications. For instance, data collected by remote-control vehicles in offshore oil and gas and renewable energy plants can be transmitted at distances of even 1 m or less. This study uses previous frequency response measurements taken in deep water to explore the capacity of a short-range electromagnetic underwater channel. Because of water movement, the nonstatic position of the vehicle when the transmission occurs means that the channel is regarded as randomly time-variant. A statistical model is proposed and the ergodic capacity is calculated for a 7 MHz bandwidth channel at distances ranging from 0.5 m to 5 m as well as for different values of transmitter power. The results of this study reflect capacity values of tens of kbps at distances of approximately 5 m to several Mbps at distances of less than 1.5 m.

scholarly journals Self-Organized Proactive Routing Protocol for Non-Uniformly Deployed Underwater Networks

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5487
Author(s):  
Waheeduddin Hyder ◽  
Miguel-Ángel Luque-Nieto ◽  
Javier Poncela ◽  
Pablo Otero
Keyword(s):  
Energy Consumption ◽  
Acoustic Waves ◽  
Time Synchronization ◽  
Sea Water ◽  
Propagation Speed ◽  
Global Navigation Satellite Systems ◽  
Wireless Sensor ◽  
Destination Node ◽  
Limited Mobility ◽  
Self Organized

Electromagnetic (EM) waves cannot propagate more than few meters in sea water due to the high absorption rate. Acoustic waves are more suitable for underwater communication, but they travel very slowly compared to EM waves. The typical speed of acoustic waves in water is 1500 m/s, whereas speed of EM waves in air is approximately 3 × 108 m/s. Therefore, the terrestrial wireless sensor network (WSN) protocols assume that the propagation delay is negligible. Hence, reactive protocols are deemed acceptable for WSNs. Other important issues related to underwater wireless sensor networks (UWSNs) are determining the position of the underwater nodes and keeping a time synchronization among the nodes. Underwater nodes can neither determine their position nor synchronize using Global Navigation Satellite Systems (GNSS) because of the short penetration of EM waves in sea water. The limited mobility of UWSN nodes and variation in the propagation speed of acoustic waves make time synchronization a challenging task for underwater acoustic networks (UASNs). For all these reasons, WSN protocols cannot be readily used in UASNs. In this work, a protocol named SPRINT is designed to achieve high data throughput and low energy operation in the nodes. There is a tradeoff between the throughput and the energy consumption in the wireless networks. Longer links mean higher energy consumption. On the other hand, the number of relay nodes or hops between the source node and the final destination node is a key factor which affects the throughput. Each hop increases the delay in the packet forwarding and, as a result, decreases the throughput. Hence, energy consumption requires the nearest nodes to be chosen as forwarding nodes, whereas the throughput requires the farthest node to be selected to minimize the number of hops. SPRINT is a cross-layer, self-organized, proactive protocol which does not require positioning equipment to determine the location of the node. The routing path from the node to the gateway is formed based on the distance. The data sending node prefers to choose the neighbor node which is closest to it. The distance is measured by the signal strength between the two nodes.

Acoustics of Corrugated Pipes: A Review

2013 ◽  
Vol 65 (5) ◽  
Author(s):  
B. Rajavel ◽  
M. G. Prasad
Keyword(s):  
Acoustic Waves ◽  
Oil And Gas ◽  
Flow Instability ◽  
Air Flow ◽  
Research Work ◽  
Industrial Applications ◽  
Structural Vibration ◽  
Sound Generation ◽  
Local Rigidity ◽  
Offshore Oil And Gas

Corrugated pipes and tubes are commonly used in many engineering and industrial applications because they offer global flexibility combined with local rigidity. Some of the engineering systems which use the corrugated pipes are Liquefied Natural Gas (LNG) storage systems, risers for offshore oil and gas industries, heat, ventilation, and air conditioning systems (HVAC), aerospace and automobile cabin cooling systems, and certain domestic appliances such as vacuum cleaners. Air flow through a short or a long length of corrugated pipes can cause the pipes to emit loud and clear “tonal” sounds or “whistling” at some critical flow conditions. Interaction and coupling of these acoustic waves with vortex shedding-flow instability can result in severe noise and structural vibration problems. A phenomenon of sound generation in corrugated pipes is also observed in a children's toy called “Hummer,” “Voice of the Dragon,” or “Magic Whistle.” This review paper focuses on the research work carried out to date to study the sound generation mechanism and its reduction methodology in corrugated pipes with air flow. This paper reviews and summarizes the various theoretical, experimental and computational work carried out in relation to acoustics of corrugated pipes.

Drilling and Service Contracts in Offshore Oil and Gas Operations

1973 ◽  
Vol 11 (3) ◽  
pp. 480
Author(s):  
J. M. Killey
Keyword(s):  
Oil And Gas ◽  
Oil Industry ◽  
Offshore Drilling ◽  
Oil Companies ◽  
Drilling Rig ◽  
Service Contracts ◽  
Oil And Gas Operations ◽  
Offshore Oil And Gas ◽  
Offshore Oil ◽  
Offshore Operations

As onshore oil and gas deposits are becoming more difficult to locate, and as the world demands for energy continue to increase at an alarming rate, oil companies are channeling much of their exploration activities towards offshore operations, and in particular, towards operations centered off Canada's coast lines. Because of the environment, offshore drilling presents problems which are novel to the onshore-geared oil industry. J. M. Killey discusses in detail many of the considerations involved in drafting the offshore drilling contract, concentrating on problems such as the liability of the various parties; costs; scheduling; pollution; conflict of laws; etc. Similarly, he discusses service contracts (such as supply boat charters; towing services; helicopter services; etc.^ which are necessity to the operation of an offshore drilling rig. To complement his paper, the author has included number of appendices which list the various considerations lawyer must keep in mind when drafting contracts for offshore operations.

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