The small-scale leak investigation is a combined experimental and modeling program. As part of the modeling effort a fast-running engineering model for the buoyant jet from a hydrogen slow leak was developed. The model computes the trajectory of the buoyant jet and the hydrogen concentration decay along the jet trajectory. Simulation times for the slow-leak engineering model are a few seconds on a computer workstation as compared to many hours for a Navier-Stokes equation simulation of the same leak. As part of the experimental effort, a planar laser-Rayleigh scattering and CCD camera technique was developed to measure real-time images of the concentration field from slow hydrogen leaks. Planar laser-Rayleigh scattering is a laser-based diagnostic technique that is sensitive to gas density and is hence well suited to accurately measure the flow behavior of hydrogen exiting a leak into ambient air.
Comparisons are made between the measured slow leak concentration fields and predictions from the slow-leak engineering model. Calculations from the model and experimental results are presented to explain the behavior of slow leaks over the Froude number range of interest.
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