Faculty Publications
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Item Impact of Building Configurations on Fluid Flow in an Urban Street Canyon(Springer Science and Business Media Deutschland GmbH, 2024) Singh, S.; Singh, L.; Jitendra Pal, S.The problem of pollution dispersion in urban areas is significant in the densely populated cities. The topography and barriers in the form of buildings impact the atmospheric fluid flow. The resulting phenomena known as pollution traps cause an artificial dispersion in the buildings’ proximity, affecting the health of ordinary road commuters. The primary source of pollution on the street canyons is exhaust gases from the vehicle movements. However, the concern is associated with the poor dispersion of pollutants under normal wind conditions. The primary reason behind the poor dispersion is the buildings that act as obstacles to the atmospheric wind flow. Thereby it is essential to comprehend the behaviour of pollutants under given shape constraints and flow conditions to improve urban air quality. The present study investigates the wind flow in the proximity of a six-storey building for a medium street canyon configuration under the logarithm inlet velocity profile that acts as atmospheric boundary layer (ABL). Effect of important parameters such as the building height, the wind direction (0, 30, 45, 60, and 90°), and building configurations (straight road, both side building, and only upwind side building with downwind side building) are investigated to gain valuable insights into pollutant dispersion. The analysis of turbulence and velocity profile in the domain at nose level (1.5 m above ground level) leeward sidewalk and windward sidewalk shows turbulent intensity decreases at the nose (breathing) level with building height; however, it increases when the approach angle is 450 suggesting the formation of dominant pockets of pollutants. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Bursting phenomenon in turbulent wall-bounded flows(American Institute of Physics, 2025) Raghuram, S.; Ramesh, O.N.The scaling of bursting period governing the near-wall turbulence production in a wall-bounded flow has been an unresolved issue in the literature, despite nearly half a century of intense research. By using measurements from a turbulent channel flow along with laboratory boundary layer and atmospheric boundary layer data available in the literature, the appropriate scaling for the inter-burst time period (time period between two consecutive bursting events) is reexamined. The bursting period, non-dimensionalized using the inner scales, varied by five orders of magnitude over the Reynolds number range of 10 3 ? 10 7 , conclusively demonstrating thereby that the bursting period does not scale on inner variables. The bursting period, non-dimensionalized using the traditional outer timescale (ratio of the channel half-height to the centerline velocity), was found to asymptote to an invariant value at high Reynolds number for laboratory boundary layer and channel data. However, when the atmospheric boundary layer data were also included, this non-dimensional timescale's invariance became weaker and showed a slowly increasing trend with Reynolds number. A new modified outer timescale, where the friction velocity is the velocity scale, resulted in invariance for Reynolds number greater than 900 and suggests possible invariance over a wider range extending to higher Reynolds numbers. The new timescale is also amenable to a simple physical interpretation as the time of transit of the up-welling eddy to reach the outer region of the boundary layer/centerline of the channel flow. © 2025 Author(s).