An extension to the universal time scale for vortex ring formation. (12th March 2021)

• Record Type: Journal Article
• Authors: Limbourg, Raphaël; Nedić, Jovan
• Is Part Of: Journal of fluid mechanics. Volume 915(2021)
• Publication Date: 2021-03-12
• Subjects: vortex dynamics, -- jets; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2021.141
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Abstract : The formation of vortex rings emanating from orifices with different orifice-to-tube diameter ratios $D_0/D_p$ is studied using time-resolved particle image velocimetry. The invariants of the motion in their non-dimensional form are computed and presented in the non-dimensional time space $t^*=U_0 t/D_0$, where the subscript 0 refers to the exhaust quantities. The classic slug-flow model is revisited and extended to account for the contraction of the flow when fluid is being pushed out through the orifice. Accordingly, a new time scale in terms of the contracted quantities (subscript $\star$ ) is defined as $T^*=U_\star t/D_\star$ . Results show that the modified slug-flow model unifies the formation number of orifices and straight nozzles with a value of approximately 4.