Research Projects

The objective of the proposed work is to understand, using theoretical and computational approaches, hydrodynamic instabilities and route to turbulence in estuarine flows, which play a key role in estuarine mixing and tracer transport. This study can help in making informed decisions toward managing coastal zone vulnerability to extreme events, including sea-level rise and anthropogenic activities, particularly along India's extensive and ecologically diverse coastline. Estuarine hydrodynamic processes are influenced by river flow, tidal current strength, bathymetry, and horizontal density gradients born out of the competition between the ocean and river waters. At present, geological, chemical, and biological parameters obtained through field observation studies primarily describe estuarine systems; thus, such studies are estuary specific. Field studies are generally expensive and sometimes inconclusive, and there is often a lack of continuous and long-term observations. Moreover, field data are often too complex and obscures the fundamental understanding of the key fluid dynamic processes. Hence, despite observational studies on estuarine circulation patterns and turbulence-induced mixing, the physical mechanism behind those phenomena remains unexplored, which is crucial for long-term effective coastal management. The overarching aim of this proposal, which is the first of its kind, is to provide a generalized fundamental understanding of estuarine hydrodynamic instability mechanisms, the route to turbulence, and the ensuing diapycnal mixing, as opposed to the conventional field-based, estuary-specific understanding. In the proposed work, by considering a simplified estuarine set-up, a mathematical model will be developed to explore the fundamental instability mechanisms and routes to turbulence in estuaries with different geometries and physical properties. High fidelity numerical simulations will be performed to understand the effect of key estuarine features (velocity and salinity profiles, along channel salinity gradient, and bathymetry) on the nonlinear flow evolution processes. Afterwards, the effect of realistic, complex estuarine geometries will be incorporated into the computational models. This analysis would reveal complex flow structures (eddies), primary and secondary instability features, the amount of turbulence-induced vertical mixing (which would, in turn, provide state-of-the-art parameterizations of eddy viscosity and diffusivity), tracer transport (sediments, pollutants, nutrients), and the impact of sea-level rise on estuarine dynamics. The results obtained from the simulations would be validated against existing field observation and experimental studies, contributing to more effective coastal management strategies in India’s rapidly changing estuarine environments.