Transverse jets and jet flames: Structure, scaling, and effects of the heat release

Many industrial combustion devices rely on turbulent jets in crossflow, also known as transverse jets, to achieve mixing and reaction. However, the literature affords limited predictive capability regarding the momentum and scalar mixing characteristics of the average flow. Detailed velocity data in the symmetry plane of the jet is relatively scarce, and the effect of heat release on burning jets has hardly been documented at all.; The first objective of the present work is to improve understanding of the transverse jet by deriving two sets of intermediate-asymptotic scaling laws, corresponding to jet-like behavior where the jet is only slightly deflected, and wake-like behavior where the jet is fully deflected. Scaling laws for velocity, scalar concentration, and jet trajectory show good agreement to data. The implied structure of the vorticity field represents a radical departure from classical concepts of the counter-rotating vortex pair.; The second objective is to measure and understand the details of the velocity field in the symmetry plane of the jet. Particle Image Velocimetry (PIV) measurements are made in the symmetry plane of cold and burning jets issuing into a wind tunnel at jet-to-crossflow blowing ratios of 10 and 20. Ensemble-averages and turbulence statistics of the velocity field are presented, and interesting features of the entrainment process in transverse jets are discussed.; Heat release affects the average flowfield markedly, with the most rapid change occurring near the base of the lifted flame. This observation motivates more detailed investigation into the dynamics of the flame base and instantaneous heat release/turbulence interactions throughout the flame. Simultaneous Planar Laser-Induced Fluorescence (PLIF) of the OH radical and PIV are employed to make direct observations of the flame/flow interaction. As the flow on the lee side passes through the flame base, for example, the average speed increases by a factor of 2–3; this effect is also observed over the flame as a whole, when compared with the non-reacting case. At the flame base, low flow speeds are often found in regions of high OH signal, implying that flame stabilization is partly governed by the availability of low-speed regions in the flowfield.