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In finding BP oil spill flow rate, lab science meets real world

Scientists are using sophisticated tools to estimate the flow of oil responsible for the BP oil spill. Some techniques are commonly used to show scientific principles, but are not often applied to real-world problems.

By Staff writer / June 11, 2010

Flow rate estimates for the gusher responsible for the BP oil spill (shown here Friday evening) have steadily risen.

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From 1,000 barrels a day at the outset to as much as 40,000 barrels a day today, estimates of the amount of oil that poured from BP's Deepwater Horizon blow-out during the event's initial 44 days have climbed.

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Early jumps in the flow rate estimates came as the scope of the disaster expanded, but more recent increases reflect the sophisticated tools scientists are now using on the flow-estimation problem.

These tools have long been used for basic science, but this may well mark the first time some of them have been applied to a real-world environmental problem.

In describing a sonar-based approach she and her colleagues are using to take the measure of the blow-out's flow, University of Georgia marine scientist Daniela Di Iorio says, "I never in my mind would have dreamed of using this to measure an oil plume." Typically, she says, she has used the technique to study underwater hydrothermal vents.

The national incident command, which is coordinating the response to the blow-out, set up its flow-rate technical group roughly a month after the blast. Within the group, four teams have emerged, each using a different approach for estimating the flow.

One of those approaches, for instance, involves analyzing high-resolution video of the plume to estimate the pace at which material is flowing. The title is a mouthful: particle image velocimetry. But the principle is simple, explains Peter Cornillon, a researcher at the University of Rhode Island's Graduate School of Oceanography who has worked with the flow-rate technical group team using the approach.

He likens it to estimating a race car's speed by using a video camera aimed at a fixed spot along the track. The difference in the car's location from one video frame to the next yields an estimate of the distance traveled. And the speed at which the camera records each individual frame provides a way to calculate the time it took the car to travel that distance.

Typically, the well-known technique is a lab tool in which the fluid is clear, and tiny particles made of anything from glass beads to soil can be used as tracers that allow scientists to see the flow patterns in the fluid.

"We don't have little glass beads in this oil plume, and it's opaque," Dr. Cornillon continues. So the team using this technique has focused its attention on individual billows in the oil plume as markers for tracking the flow.

Billows change quickly with time, but with the software packages scientists use to analyze the videos, "you can come up with a pretty reasonable estimate of how far it moved," he says.

Help also has come from outside the core technical group. Scientists from four academic institutions, led by the Woods Hole Oceanographic Institution's Richard Camilli, have been pinging the plume with two types of sonar mounted on a small remotely operated undersea vehicle.

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