Aerodynamics of Axisymmetric Counterflowing Jets

Abstract

The laminar flow resulting from impingement of two steadily fed low-Mach-number gaseous jets issu- ing 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 nearlyinviscid, with viscous effects and mixing being restricted to the thin mixing layers surrounding the jetsand to a thin layer located at the separating stream surface. The analysis of the main inviscid flow showsthat only two parameters, based on the scales associated with the radius and the velocity profiles of thetwo feed streams, are needed to characterize the flow, namely, the ratio of the inter-jet separation dis- tance to the duct radius and the ratio of momentum fluxes of the jets. The numerical results for uniformand Poiseuille velocity profiles provide, in particular, the value of the strain rate at the stagnation pointfor use in the analysis of experimental studies of counterflow premixed and diffusion flames.