An Evaluation of the Frequency Response of Hydrocarbon Droplets

TitleAn Evaluation of the Frequency Response of Hydrocarbon Droplets
Publication TypeConference Abstract
AuthorsLoranger, S, Weber, TC
Conference Name171st Meeting of the Acoustical Society of America
Conference LocationSalt Lake City, UT
Conference DatesMay 23-27
Keywordsfrequency response, hydrocarbon

Development of instrumentation to detect and quantify submerged oil droplets would provide researchers and oil spill responders with crucial information about the fate and movement of oil in the environment. By detecting oil droplets in the watercolumn it should be possible to trace surface sheens to their source and to determine the location and extent of plumes of oil at depth. Methods of detecting oil currently exist, for example, mass spectrometers and fluorometers; however, they are limited to detecting oil that is submeter range from the instrument. Using broadband high frequency (30–300 kHz) acoustic echosounders, it is possible to not only detect oil droplets from a greater distance (10s of meters for individual droplets, depending on the background noise) but to quantify the physical properties of the oil, including the size of droplets. Droplet size is an important factor in determining the likely location of submerged plumes and surface sheens, the rate of biodegradation and rise rate of oil. Laboratory measurements of the broadband response along with the sound speed, density and droplet size of crude oil, diesel, gasoline, and kerosene have been made. The frequency response of the droplets have been compared to models for the target strength of fluid filled spheres to verify the models, and to empirically derive adjustments if necessary. The data are also used to empirically estimate a detection range limit for different densities of droplets determined.