ATOMISATION AT EXTREME FLOW CONDITIONS
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Aerobreakup is a process of deformation and fragmentation of a droplet subjected to high-speed gas flow. It has various natural and industrial applications like raindrop formation, spray systems, fuel atomization, energy systems, aerospace, agriculture, medicine and food industries; recently, even for modelling disease transmission. In all such cases, the size distribution of the fragmented droplets is a critical parameter.
Droplet aerobreakup is a transient phenomenon involving complex interfacial dynamics. This typically involves destabilization of the interface under the aerodynamic influence of highspeed gas flows, leading to the formation of unstable waves. This is typically represented by the Weber number (We) and other non-dimensional numbers. The waves constitute subsequent deformation to the interface, forming a non-linear wave cascade.
The undulation, originating from shear-driven or Kelvin-Helmholtz (KH) instability, undergoes a breakup cascade involving the next generation of wave mechanisms (Rayleigh Taylor RT and Rayleigh Plateau RP instability). These local events or sub-secondary atomization processes are reminiscent of a droplet breakup, indicating a self-similar cascade. The daughter droplet sizes also depict a self-similar distribution.
We are pursuing a model that describes the aerobreakup and interfacial dynamics due to impulsive flow behind a shockwave. Broad objectives:
(a) Developing effective experimental techniques - Optical Measurement Methods
(b) Development of an accessible experimental setup - Wire-blast based Shocktube
(c) Investigating the physics of aerobreakup - Advancement of interfacial dynamics and breakup analysis.
VORTEX DOMINATED FLOWS
SOAP BUBBLE INFLATION
SOAP BUBBLE INFLATION
Bubbles have always captivated our curiosity with their aesthetics and complexities alike. While the act of blowing bubbles is familiar to everyone, the underlying physics of these fleeting spheres often eludes reasoning. In this Letter, we discuss the dynamics of inflating a soap bubble using controlled airflow through a film-coated nozzle. We assess and predict the rate of inflation by varying the source pressure. Visualizing the previously unexplored internal flow reveals that air enters the bubble as a round jet, emerging from the nozzle opening and impinges on the expanding concave bubble interface to form a toroidal vortex. Several scaling laws of the associated vortical flow spanning the entire bubble and the vortex core are reported. The observed dynamics of this bubble-confined vortex ring formation indicate universality in certain aspects when compared to the free laminar vortex rings.
BLAST-INDUCED COMPRESSIBLE VORTEX RINGS
BLAST-INDUCED COMPRESSIBLE VORTEX RINGS
We investigate the flow field induced by blast waves or unsteady shock waves at the shock tube exit. A miniature shock tube with the wire-explosion technique produces blast waves, facilitating a wide range of Mach numbers (1.1-2). The blast exiting the shock tube diffracts at the inner tube lip, and the induced flow rolls up to form a compressible vortex ring with a trailing jet. Fundamental understanding of of such compressible unsteady airflow is crucial and a few application areas include:
Rocket or missile nozzle design
Manoeuvring devices for Aerospace applications (Aircraft, rockets, satellites)
Compact shock tube design
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