Exothermicity and Relaminarization Effects in Unsteady Reactive Square Jets

Abstract

We present results of numerical simulations of the near field of unsteady reactive square jets. The jets studied are compressible (subsonic) and consist of hydrogen diluted in nitrogen emerging into a quiescent background of oxygen also diluted in nitrogen. The numerical model involves space/time developing jets, species- and temperature-dependent diffusive transport, and finite-rate reduced chemistry appropriate for hydrogen combustion. The study focuses on investigating the role of exothermicity and relaminarization in controlling the jet development, and the dependence of these effects on Reynolds (Re) and Lewis (Le) numbers. For the flow regimes studies, considerable viscous damping effects are found for the reactive jets because of exothermicity and the monotonically increasing dependence of viscosity with temperature-in contrast with slight stabilizing effect of reducing Re in absence of chemical reactions. The reactive simulations predict generally higher jet temperatures and significantly reduced jet entrainment associated with lower Re and jet Le less than unity.