Aerodynamics of axisymmetric counterflowing jets

The laminar flow resulting from impingement of two steadily fed low-Mach-number gaseous jets issuing into a stagnant atmosphere from coaxial cylindrical ducts at moderately large Reynolds numbers, often used in combustion experiments, is studied through numerical integrations of the Navier–Stokes equations. In the Reynolds-number range addressed, 50–1000, the flow of the approaching jets is nearly inviscid, with viscous effects and mixing being restricted to the thin mixing layers surrounding the jets and to a thin layer located at the separating stream surface. The analysis of the main inviscid flow shows that only two parameters, based on the scales associated with the radius and the velocity profiles of the two feed streams, are needed to characterize the flow, namely, the ratio of the inter-jet separation distance to the duct radius and the ratio of momentum fluxes of the jets. The numerical results for uniform and Poiseuille velocity profiles provide, in particular, the value of the strain rate at the stagnation point for use in the analysis of experimental studies of counterflow premixed and diffusion flames.