Dual vortex breakdown in a two-fluid whirlpool

Abstract

Looking for an optimal flow shape for culture growth in vortex bioreactors, an intriguing and impressive structure has been observed that mimics the strong swirling flows in the atmosphere (tornado) and ocean (waterspout). To better understand the flow nature and topology, this experimental study explores the development of vortex breakdown (VB) in a lab-scale swirling flow of two immiscible fluids filling a vertical cylindrical container. The rotating bottom disk drives the circulation of both fluids while the sidewall is stationary. The container can be either sealed with the still top disk (SC) or open (OC). As the rotation strength (Re) increases, a new circulation cell occurs in each fluid—the dual VB. In case SC, VB first emerges in the lower fluid at Re = 475 and then in the upper fluid at Re = 746. In case OC, VB first emerges in the upper fluid at Re = 524 and then in the lower fluid at Re = 538. The flow remains steady and axisymmetric with the interface and the free surface being just slightly deformed in the studied range of Re. Such two-VB swirling flows can provide efficient mixing in aerial or two-fluid bioreactors.

Influence of nano- and micro-roughness on vortex generations of mixing flows in a cavity

“…For this reason, a long-term visualization for a more accurate determination of the vortex boundary was therefore used. 11,18 Small local Reynolds numbers corresponding to flow with very low velocities on the stationary boundary without pulsations permitted recording of a visual picture of the flow quite well. The flow visualization by a laser light knife with a thickness of 1 mm in the central cross-section of the cylinder was used to study the topology of the vortex cell.…”

“…9 Indeed, in recent years, many industries, such as medicine, microbiology, pharmaceutical, petrochemical industries, etc., require soft but effective mixing of liquids, including those with variable viscosity, without the formation of foam, water hammer, cavitation, high-turbulence, and stagnant zones. 10,11 From the point of view of the use of vortex mixing technologies for Kitchen Flows in contrast to traditional mixing devices with mechanical or magnetic stirrers, this is mainly to ensure gentle (non-traumatic) mixing of bio cultures beneficial to the body during the formation of various yogurts, creams, healthy, or baby meals. In the gentle mixing mode, due to the organization of the vortex movement not with a mechanical stirrer but a rotating disk without blades, when the foam is not formed, useful bio cultures are not destroyed at the cellular level, thus increasing the "usefulness" of the manufactured product and the concentration of living microorganisms.…”

Thermal hydraulic performance of a tubular heat exchanger with in‐line perforated baffle with shutter type saw tooth turbulator

“…For instance, they prevent flow bypassing in heat exchangers with parallel flow passages, thus boosting overall heat transfer performance. In practical terms, swirl flow finds applications in various devices that do not involve chemical reactions, such as vortex amplifiers, 2,3 reactors, heat exchangers, cyclone separators, 4 whirlpools, 5 and jet pumps 6 . However, in cases where chemical reactions are involved, swirling devices are extensively used in combustion systems, including industrial furnaces, gas turbines, 7 gasoline and diesel engines, boilers, and heating appliances.…”