Determining the discharge rate from a submerged oil leak jet using ROV video

• We describe a technique to measure the flow rate of submerged turbulent jets using video.
• This technique was first applied to the Deepwater Horizon oil leak by the Flow Rate Technical Group.
• Experiments in the UC Berkeley Tow Tank were conducted using dye-colored water jets.
• The dye colored water jets were measured with high speed video and laser Doppler anemometry (LDA).

With expanded deep sea drilling in the Gulf of Mexico, and possibly the Arctic, it is imperative to have a technology available to quickly and accurately measure the discharge rate from a submerged oil leak jet. This paper describes an approach to measure the discharge rate using video from a Remotely Operated Vehicle (ROV). ROV video can be used to measure the velocity of visible features (turbulent eddies, vortices, entrained particles) on the boundary of an oil leak jet, from which the discharge rate can be estimated. This approach was first developed by the Flow Rate Technical Group (FRTG) Plume Team, of which the authors Savaş and Shaffer were members, during the response to the Deepwater Horizon (DWH) oil leak. Manual tracking of visible features produced the first accurate government estimates of the oil discharge rate from the DWH. However, for this approach to be practical as a routine response tool, software is required that automatically measures the velocity of visible features. To further develop this approach, experiments were conducted to simulate a submerged oil leak jet using a dye-colored water jet in the U.C. Berkeley Tow Tank facility. Jet exit diameters were 10.2 cm and 20.3 cm. With flow rates up to 11 gal/s, Reynolds numbers in the range of the DWH oil leak jets (up to 500,000) were achieved. The dye-colored water jets were recorded with high speed video and radial profiles of velocity were mapped with Laser Doppler Anemometry (LDA). Particle Image Velocimetry (PIV) software was applied to measure the velocity of visible features. The velocities measured with PIV software were in good agreement with the LDA measurements. Finally, the PIV software was applied to ROV video of the DWH oil leak jet. The measured velocities were 10–50% lower than manual measurements of velocity. More research is required to determine the reasons why PIV software produced much lower velocities than manual tracking for the DWH oil leak jet.