Methane dispersion in a zero-pressure-gradient boundary layer flow at large Reynolds number*

The dispersion of methane gas released from a vertical pipe in a zero-pressure gradient boundary layer flow at large Reynolds number is investigated. A gaseous mixture of 5% methane and 95% nitrogen by volume is injected into the boundary layer in a jet in crossflow arrangement where the jet exit is h_s/δ ≈ 0.6 above the floor of the test section, where h_s is the source height and δ is the boundary layer thickness. Three jet-to-crossflow velocity ratios and three source configurations are investigated. The source configurations consist of a straight vertical pipe and two concentric pipes with aspect ratio AR (outer diameter/inner diameter) = 10.67 and 21.33. The source diameter (inner diameter) is fixed in all three configurations. Methane concentration downstream of the source is acquired using an Aeris Technologies MIRA Ultra LDS. The downstream evolution of the methane jet is characterized and the underlying mechanisms controlling the scalar dispersion are investigated.