Lagrangian simulation of a jet-in-crossflow at a finite Reynolds number

In this paper, the vorticity dynamics of a transverse jet at Re _jet = 1715 and r = 7 is analyzed by the use of a computational model based on vortex element methods. This study extends our previous computational studies of inviscid transverse jets.^9-11 The diffusion of the vorticity field is treated by a modified interpolation kernel, developed from the concept of the vorticity redistribution.¹⁴ The results of computation show the essential behavior of the viscous transverse jet, including the rollup of the jet shear layer and the formation of the counter-rotating vortex pair. The mechanism behind the formation of the counter-rotating vortex pair is also investigated by tracking the material line elements introduced as rings at the jet nozzle exit. The underlying mechanism of the formation of counter-rotating vortex pair shows similarity to the mechanism observed in our previous inviscid simulations,^10,11 which confirms the robustness of the mechanism proposed. The jet trajectory is obtained by computing the averaged centerline streamline, and is compared to the scaling laws.³ The streamline does not agree to the near-field scaling law, but the far-field scaling law still shows validity, since the 1/3 power law has been recovered for the later stage of the jet.