Aerodynamics of planar counterflowing jets

Abstract

The planar laminar flow resulting from the impingement of two gaseous jets of different density issuing into an open space from aligned steadily fed slot nozzles of semi-width $H$ separated by a distance $2L$ is investigated by numerical and analytical methods. Specific consideration is given to the high Reynolds and low Mach number conditions typically present in counterflow-flame experiments, for which the flow is nearly inviscid and incompressible. It is shown that introduction of a density-weighted vorticity–streamfunction formulation effectively reduces the problem to one involving two jets of equal density, thereby removing the vortex-sheet character of the interface separating the two jet streams. Besides the geometric parameter $L/H$, the solution depends only on the shape of the velocity profiles in the feed streams and on the jet momentum-flux ratio. While conformal mapping can be used to determine the potential solution corresponding to uniform velocity profiles, numerical integration is required in general to compute rotational flows, including those arising with Poiseuille velocity profiles, with simplified solutions found in the limits $L/H\ll 1$ and $L/H\gg 1$. The results are used to quantify the near-stagnation-point region, of interest in counterflow-flame studies, including the local value of the strain rate as well as the curvature of the separating interface and the variations of the strain rate away from the stagnation point.

Aerodynamics of Tsuji Burners with Augmented Fuel Injection

“…Consideration of the limit Re 1 will be seen to reduce the problem to that of inviscid flow, with the solution depending in general on two parameters, namely, the fuel-to-air density ratio ρ F /ρ A and the fuel-to-air velocity ratio U i /U c . Use of a densityweighted vorticity-streamfunction formulation [4,5] further reduces the problem to the constant-density case, with Λ = (ρ F /ρ A ) 1/2 U i /U c entering as the only governing parameter.…”

“…The free-boundary problem defined in (2.12)-(2.15) determines ψ(r, θ) along with the vorticity distribution ω w (θ) and the separating surface r s (θ) for given values of U i /U ∞ and ρ F /ρ A . As shown in [4,5], the solution can be simplified by incorporating a renormalization factor (ρ F /ρ A ) 1/2 in the definition of new kinematic variables…”