Application ID: APWRD23RA1046

 



Brief Details:

Dr. Abhishek is currently working as a post-doctoral fellow in the civil engineering discipline at IIT Bombay. He joined IIT Gandhinagar to pursue Ph.D. from July 2016 to May 2022, directly after completing his B.Tech. from NIT Patna. He was selected as a start-early Ph.D. fellow in the civil engineering discipline. He was also selected for the Prime Minister Research Fellowship (PMRF) in 2018. He taught Fluid Mechanics to undergraduate students for a semester as a Graduate Trainee Fellow (GTF) at IIT Gandhinagar. During his Ph.D., he advanced the understanding of flood flow, sediment and mass transport, and three-dimensional hydrodynamics of channel junctions. He conducted both experimental and numerical simulations (3D CFD simulations) of the channel junction. He is a member of a professional society: “International Association for Hydro-Environment Engineering and Research (IAHR).” His expertise includes experimental and computational hydraulics (3D CFD modeling). His recent paper “Flow Dynamics and Pollutant Transport at an Artificial Right-angled Open-Channel Junction with a Deformed Bed” got featured in the Editor’s Choice of the ASCE’s Journal of Hydraulic Engineering. Dr. Abhishek is primarily interested in solving problems related to flooding and sedimentation. 

Title of Talk:  Flow Dynamics and Pollutant Transport at a Right-Angled Open Channel Junction with a Deformed Bed

Abstract: Open channel junction flow occurs in natural and human-made (e.g., drainage systems) hydraulic systems. A proper understanding of the channel junction flow dynamics is essential to analyze the associated physical processes at the junction. This research seminar presents a detailed three-dimensional (3D) flow field and pollutant transport at a laboratory-scale right-angled channel junction with a quasi-equilibrium deformed bed to elucidate the hydraulics of the channel junction. 3D turbulent structures and their role in pollutant transport are examined using the Large-eddy simulation (LES) model. The deformed bed junction represents a quasi-equilibrium condition and consists of a scour zone and deposition bar. The quasi-equilibrium deformed bed of the junction is obtained from the initial flat-bed condition. The numerical model is validated against experimental data of the velocity field. The study shows that bed topography plays a major role in controlling flow and turbulent structures at the junction. The flow field, including the 3D turbulent structures, is modified remarkably at the deformed bed junction compared to the field under the initial flat-bed condition. Comparisons of the flow field between the flat-bed condition and quasi-equilibrium, deformed bed condition demonstrate a reduced flow separation zone and less-developed recirculating gyre in the latter case because of the strong secondary currents. Visualization of the turbulent structures using the Q-criterion shows the dominance of the turbulent structures generated from the Kelvin–Helmholtz (KH) instability of the shear layer over the streamwise-oriented vortical structures at the junction. The coherence of the turbulent structures is drastically disrupted at the deformed bed junction as the KH instability results in more randomly oriented residuals. In contrast, the breakdown of the shear layer at a flat-bed junction displays the trail of the arch-shaped vortices. In this work, the role of turbulent structures in pollutant transport is elucidated by using a neutrally buoyant, conservative tracer. Large incoherent turbulent structures associated with the KH instability help the tracer evolve faster at the deformed bed junction. The present study improves the understanding of the flow field and mixing patterns at the open channel junctions.

Teaching: Rapidly Varied Flow: Hydraulic Jump

 Abstract: The topic: “Rapidly Varied Flow: Hydraulic Jump” will be covered in the teaching seminar. The hydraulic jump has been chosen for this teaching seminar as it is a very intriguing and interesting free surface phenomenon and has been studied extensively by hydraulic engineers and researchers. The common occurrence of the hydraulic jump includes its application as an energy dissipator to dissipate the excess energy of flow downstream of hydraulic structures, such as sluice gates and spillways. The seminar will present the “Introduction” to this interesting phenomenon, which includes its definition, types, importance, and practical applications. A mathematical formulation for predicting the sequent depth by applying the momentum conservation for a rectangular, horizontal and frictionless channel will be derived. The equation to predict the energy loss will be delivered in the seminar. The teaching session will also briefly cover the hydraulic jump on the non-rectangular channel. The teaching session will be delivered using the board work and slide show.


Google Scholar Link: 

https://scholar.google.com/citations?user=yVExtDQAAAAJ&hl=en


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