Development and scaling of turbulent, twin round jets

Abstract

The velocity field of stationary, turbulent, twin round jets has been found to scale with an intrinsic velocity and length, both depending linearly on inflow plane parameters-jet velocity, diameter and distance between jets. Flow fields were obtained from large-eddy simulations at these conditions in two experiments: (1) at Reynolds number based on and, and; and (2) at,. Each jet develops independently and then merges into a single jet with an elliptic cross-section. Downstream, the jet becomes circular after a mild overshoot. Close quantitative agreement with experiment was obtained in all cases. As the merged jets develop, fluctuation levels over a central half-width are nearly uniform and scale with the local maximum mean velocity. In all cases, the mean streamwise velocity along the centreline of the configuration, rises to a peak at a distance from the inflow plane. The velocity decreases and increases with. For all nozzle spacings, a similar development was observed: is a function of distance only, and is essentially independent of and. Further, these intrinsic and input quantities are connected by simple relations: and. The far field development of the merged jet can also be scaled with and, analogous to round jet scaling with and. Thus all twin round jets may be described by these new intrinsic scales.