Passive scalar (pollutant) transport in indoor and outdoor flows
Embedded Files
Indoor pollutant dispersion: ventilation time-scales and transport mechanisms
Indoor air quality is critical for public health. We investigate the flow through a hollow cube, a scaled-down model building, as an idealized representation, with an indoor ground-level passive scalar source, immersed in a rough-wall turbulent boundary layer. The focus is on characterizing scalar transport within the cube.
Pollutant transport through hollow bodies with upstream source
Understanding how turbulent processes transport and disperse air pollution into buildings is crucial for urban planning and occupancy comfort. We investigated an outdoor ground-level source placed upstream to the model where we capture the mean and transient behaviours of a scalar and the velocity fields.
Flow over bluff-bodies in a boundary layer
We studied aerodynamic forces and wake dynamics acting on wall-mounted bluff-bodies of different shapes, by combining scaled wind tunnel experiments and computational fluid dynamics (CFD) simulations. By characterising the flow behaviour and validating predictive models, the study seeks to enhance the reliability of model-based risk assessment tools and improve operational safety in different areas, for example, building safety and pedestrian comfort in urban environments.
Vortex-bubble/particle interactions
Bubble/particle-laden turbulent flows involve the complex interaction of many bubbles/particles with vortical structures having a range of length scales. My work investigates an idealization of these flows, namely, the interaction of a vortex ring with air bubble(s)/particles, looking into several aspects related to their two-way coupled interaction, to better understand bubbles' interaction with vortices.
How critical is bubble's deformability?
In most studies on bubble deformation and breakup in turbulence, the influence of bubble size is not considered independently. However, alongside Weber number, bubble size can also be a critical parameter since it influences the bubble’s dynamical characteristic.. I studied the interaction of a single vortex ring with a deforming air bubble, at different bubble-to-vortex ring size ratios.
Journal of Flow Visualization and Image Processing 27 (1), 1-27
Vortex in a bubbles swarm:
Effect of single and multiple bubbles on a thin vortex ring The focus here is on the interaction of multiple air bubbles (a swarm) with a single vortex ring formed in water. This builds upon the single-bubble study, adding the complexity of many bubbles. As the ring travels through the swarm, it continuously captures bubbles, resulting in a time-varying ratio of total bubble volume within the ring to the ring volume. This leads to more dramatic interactions, weakening the ring faster than in the single-bubble case.
Effects of Bubble Size:
In bubbly flows, the deformability of bubbles is critical in governing the dynamics of both the carrier and dispersed phase. To better understand this aspect, I studied the interaction between a rigid buoyant particle (a non-deforming bubble) and a vortex ring, and compared it with bubble–ring interactions.
Particle interaction with vortex
This work investigates the interaction of a buoyant (rigid) spherical particle with a single translating (water) vortex ring. The particle within the core undergoes radial oscillation, spins and translates along the ring’s azimuthal axis. The differences in the particle size and its motion within the ring lead to large differences in the ring’s dynamics.
Skin-friction reduction in bubbly turbulence
Many bubble drag reduction (BDR) applications occur in contaminated environments. I studied the effects of salt concentration on bubble dynamics and drag modification in a fully developed horizontal turbulent channel flow. Increasing salt concentration reduces bubble coalescence, producing smaller bubbles that change deformability, migration, and distribution., and thus modifying the overall drag regimes.
Fluid-structure interactions
Fish-like propulsion: thrust generation using 2-D and 3-D flapping foils Fish use flapping motions to generate thrust, with the oscillating tail as the primary propulsion mechanism. Studying these motions helps understand and mimic efficient thrust generation. I experimentally studied thrust from sinusoidal pitching motion of rigid, flexible, and hybrid foils of varying shapes in a uniform flow at different pitching amplitudes, Reynolds number, and flexibilities. The transient shapes of the flexible foils were characterised using image processing and correlated with measured unsteady forces and moments from a load cell.
Masters Thesis, IISc 2015
Page updated
Google Sites
Report abuse