Underwater plumes

Plumes in Water Several fine researchers have approached the study of underwater plumes with different objectives. While all this work is undoubtedly instructive, a series of articles [28-32] produced by Webster and Weissberg and their colleagues may apply most directly. They have examined the structure [28] of plumes in controlled experiments and produced photographs of dye plumes to study their development. They also took the point of view of a hungry crab [32], In its attempt to find the food source indicated by the plume, the crab manipulates its sensors within the plume. The structure of the plume makes it necessary. Chapter 5 is devoted to a description of these plumes. 

Short RT, Toler SK, Kibelka GPG, Roa DTR, Bell RJ, Byrne RH (2006) Detection and quantification of chemical plumes using a portable underwater membrane introduction mass spectrometer. Trends Anal Chem 25 637-646... 

Turbulence is not the asset in water that it is in air. In air, we saw that some turbulence is required to bring the molecules out of the chemical boundary layer. That may also be needed in water to move molecules away from the bottom surface. Turbulence away from the surface tends to break up the plumes of molecules that are diagrammed in Figure 4.4. Those plumes are the key to successful detection of an underwater object that is releasing the molecules of interest. One result of the ONR experiment at San Clemente Island, off San Diego, California, was a better understanding of the formation, persistence, and dissipation of these plumes. When a well-formed plume is available, it often becomes possible to follow it to its source see Chapters 5 and 6. 

The second box contains a peristaltic pump and a servoactuator. Both the pump and servo are controlled electrically from the sensing head and are powered from the same power supply. The separation of the sensing head from the pump and servo provide electrical and mechanical isolation and address space constraints associated with mounting the system on the autonomous underwater vehicle. The peristaltic pump enables operation at a variable flow rate and has bidirectional flow capability. The servo actuates a movable sample inlet tube that can be raised or lowered by remote control to enable precise positioning of the inlet relative to the source or in the source plume. 

To our knowledge, this is the first demonstration of a sensor capable of realtime detection of a TNT plume in the marine environment at standoff distances (up to 100 m from the source) while deployed on an autonomous underwater vehicle. The sensor has shown virtually no sensitivity to chemical interferent during testing in the marine environment. While the sensitivity of the detector is excellent, its sensitivity is not adequate at its present state of development to... 

In 2001, the Fido system was modified to operate underwater and became known as the SeaDog. The U.S. Navy Office of Naval Research (ONR), under its Chemical Sensing in the Marine Environment (CSME) Program, funded the integration of the SeaDog with an autonomous underwater vehicle (AUV). The integrated system was able to map a plume of trinitrotoluene (TNT) in open water in real time. This was the first demonstration of the mapping of an explosive plume underwater in real time [9, 10],... 

Takahashi E. and Nakajima K. (2002) Melting process in the Hawaiian plume. In Hawaiian Volcanoes Deep Underwater Perspectives, Vol. Geophysical Monograph 128 (eds. E. Takahashi, P. W. Lipman, M. O. Garcia, J. Naka, and S. AramaM). American Geophysical Union, Washington, DC, pp. 403-418. 

The U.S. Navy performed field tests which successfully demonstrated that an underwater version of the Nomadics sensor can detect a plume of TNT in real-time in the ocean over 100 metres from its source. In these tests, the SeaPup sensor was integrated with the REMUS (Remote Environmental Monitoring UnitS) unmanned underwater vehicle (Figure 6) and deployed in a series of successful missions in the Atlantic Ocean. 

Figure 7. Detection of a TNT plume in the marine environment with the sensor mounted on an underwater autonomous vehicle.

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