TL;DRAbstract
In this study we explore the effect of buoyancy in controlling vortex breakdown (VB) in swirling jets. The experimental apparatus consists of a vertical swirling water jet which discharges into a large tank, in which the temperature difference between the jet and its surrounding is controlled. Three non-dimensional parameters govern the flow: the jet exit Reynolds number, the swirl ratio and the Richardson number (buoyancy). Vector maps of the vertical mid-plane and horizontal cross-sections are obtained by PIV measurements. It is demonstrated that VB can be effectively suppressed (enhanced) by prescribing a negative (positive) temperature difference between the jet core and its surrounding fluid. Moreover, the experimental critical swirl ratio for the appearance of VB agrees with a value predicted by simple criterion. Finally, the transition of VB from a closed bubble to an open cone configuration is mapped in terms of the Reynolds and Richardson numbers.
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In this study we explore the effect of buoyancy in controlling vortex breakdown (VB) in swirling jets. The experimental apparatus consists of a vertical swirling water jet which discharges into a large tank, in which the temperature difference between the jet and its surrounding is controlled. Three non-dimensional parameters govern the flow: the jet exit Reynolds number, the swirl ratio and the Richardson number (buoyancy). Vector maps of the vertical mid-plane and horizontal cross-sections are obtained by PIV measurements. It is demonstrated that VB can be effectively suppressed (enhanced) by prescribing a negative (positive) temperature difference between the jet core and its surrounding fluid. Moreover, the experimental critical swirl ratio for the appearance of VB agrees with a value predicted by simple criterion. Finally, the transition of VB from a closed bubble to an open cone configuration is mapped in terms of the Reynolds and Richardson numbers.
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