The role of turbulent inflow on the development of a round jet in cross-flow.

Abstract

The behavior of jets in cross-flow is important to fields ranging from turbine-blade cooling and fuel injectors to volcanic eruption dynamics. While previous work focused on evaluating the jets in irrotational cross-flow, this analysis is focused on the interaction between a turbulent jet in low and highly turbulent cross-flow created by an active grid (u′/U¯≈3−6% and 16−25% respectively). Mean flow statistics are collected using particle image velocimetry (PIV) for various jet-to-cross-flow velocity ratios, Rv, which allow for computation of Reynolds stresses and mean trajectories. The coordinate system is transformed to provide the relative velocities and Reynolds stresses normal and tangential to the centerline of the jet. Analysis is focused on four stages: a) quantification of the differences in the development of the jet and lee-side wake region, b) identification of the jet and cross-flow boundary (JCB), c) decomposition of the flow structures to identify and remove the highest-order contributions to turbulence kinetic energy and d) analysis of the transport to compare inertial and Reynolds stress contributions to momentum and energy. The analysis identified that the turbulence does not influence the near-field development but does increase the radius of the JCB. Removal of the highest-order features reduces the half-width of the jet and allows for measurement of the transport through the leading edge and lee-side. This shows that the turbulent inflow reduces the size of the lee-side wake region and the corresponding transport through the lee-side JCB. On the leading edge, the magnitude of entrained momentum doubles and energy increases an order of magnitude as the JCB is able to expand into the cross-flow.