Senior Project Manager Collins Engineers, Inc. Eau Claire, WI
Abstract Description: Below water environments can be hazardous. While diving equipment allows humans to explore, inspect, and report on findings below water, some conditions are simply too dangerous to allow for diving. Around dams, moving water can be too fast for a diver to navigate, the water depth can be so great that little down time is available, or physical constraints can render a dive impossible. So, what options do dam owners have when diving is not possible? Accoustic imaging can provide data from down below that will help direct decisions from up above.
Acoustic images of underwater objects are a collection of data points rendered in three-dimensional plots by a computer. This cloud of points is recorded by emitting a sound wave, capturing the sound echo off an object, and recording the time the sound traveled. With the known speed of sound through water, distances from the sound emitting head to an object which provided the echo can be calculated. Sound is emitted and echoes captured in all directions. The points from which the echoes come from are a function of the sound velocity, time, and angle of emission. A computer can make these calculations seemingly instantaneous and plot these point clouds to render an acoustic image of objects underwater.
Sonar capable of generating acoustic images can be deployed in a wide range of water conditions. In fast water, the sonar head can be deployed from a boat. In deep water, a tripod supporting the sonar head can be lowered from the water surface to the streambed. The sonar can also obtain images of a structure throughout the water column as it is lowered and raised. Since the acoustic images are derived from sound moving through water, the clarity of water does not impact results. Additionally, lights are not required so acoustic images can be obtained in the dark. Acoustic images can be obtained in nearly any water condition.
Results of acoustic images can paint clear pictures. They can define the extents of an object or structure. They can show the depth of a channel under the bottom of an exposed foundation. An acoustic image can be obtained of a debris pile in front of a trash rack in water that does not allow visibility through a camera on an ROV. With clear pictures from below, dam owners can make informed decisions up above.
Learning Objectives:
Gain insights into deploying acoustic imaging equipment.
Learn how to produce high-quality acoustic images.
Understand what critical data can be obtained from acoustic images.
