The Recirculation Zone Characteristics of the Circular Transverse Jet in Crossflow

Abstract

Transverse jets in crossflow are widely used in energy systems, especially as dilution air jets, fuel/air mixers, and combustion equipment, and have received extensive attention and plenty of research. However, the studies of the circular transverse jet issued from a circular gap at the circumferential direction of a tube in crossflow are very limited. This paper studies a relatively new jet: the circular transverse jet. Firstly, numerical calculations are conducted under different turbulence models but with the same boundary conditions. By comparing the numerical results of different turbulence models with the existing experimental data, the turbulence model which is most suitable for the numerical calculation of the circular transverse jet is selected. Then, this turbulence model is used to calculate and analyze the flow field structure and its characteristics. It is found that due to the aerodynamic barrier effect of the high-velocity jet, a negative pressure zone is formed behind the jet trajectory; the existence of the negative pressure zone causes the formation of a vortex structure and a recirculation zone downstream the circular transverse jet; and the length/width ratio of the recirculation zone does not change with the changes of the crossflow and the jet parameters. It means that the recirculation zone is a fixed shape for a definite device. This would be fundamental references for the studying of fuel/air mixing characteristics and combustion efficiency when the circular transverse jet is used as a fuel/air mixer and stable combustion system.

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“…Vortical structures associated with recirculation zones are generated in confined buildings mainly by flow separation, jet dispersion, airflow interaction around objects, or thermal plumes. Jet dispersion has been widely documented in fluid mechanics ( Li et al, 2020 ), and it presents the formation of recirculation flow around the jet (see Fig. 1 a), as reported by ventilation studies conducted by Tacutu et al (2019 , 2021 ).…”

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“…From Figure 7, it was noticed that there was a recirculation flow just above the surface level of the vegetable oil (Zone A). The formation of the recirculation zone is caused by the existence of an axial-symmetric vortex structure due to the sucking effect of the negative pressure zone, which leads to the reverse flow of the fluid [37]. Recirculation flow increases the chances for the attraction between the particles due to the attractive capillary force.…”

Study of Tangential Effusion Cooling of a Combustor Liner

“…Li [32] compared the numerical results of different turbulence models with the existing experimental data for a transverse jet in a crossflow, which is similar to the situation of the cooling jets from the effusion holes in the hot mainstream, and found that different turbulence models have different prediction accuracies, as shown in Table 3.…”

“…Table 3. Prediction accuracy under different turbulence models for a transverse jet in a crossflow [32].…”