Member Profile

Mr Smruti Jena

PhD Student

Research School of Earth Sciences
Australian National University

smruti.jena@anu.edu.au

Bachelors in Mechanical Engineering (2015) Master’s in Fluid & Thermal specialization (2017)

Biography

Smruti received his Bachelors in Mechanical Engineering in 2015. He proceeded to a Master’s degree in Fluid & Thermal specialization in Indian Institute of Technology Guwahati (IITG) graduating in 2017. During his Masters he worked on the analysis of turbulent wake flow past a triangular cylinder using an in-house RANS (standard k-epsilon method based) code over a hybrid unstructured framework and carried forward the development of a turbulent axisymmetric flow solver. He is now enrolled as a doctoral candidate in the Research School of Earth Sciences, ANU. Here, he will be using Numerical simulations (DNS, to be specific) as a tool to analyse the closed basin circulation (dynamically similar to North Atlantic Ocean) forced by both wind and buoyancy.

THESIS: Understanding the role of convection in geostrophic circulation

Ocean circulation plays a crucial role in the global climate through the uptake and transport of heat, carbon dioxide, and vital nutrients. It is also responsible for 30% of the poleward heat transport leading to a more uniformly temperate distribution. Ocean circulation involves motion at a vast range of length scales, from turbulent mixing of energy at millimetre scale, on to vertical convection at kilometre scale, to currents that travel 10,000km and large-scale gyre recirculation across ocean basins. Surface fluxes of buoyancy and momentum act as primary energy inputs to the circulation; however, the nature of the surface buoyancy contribution and the role of convection are still poorly understood. This raises the argument about the relative roles of buoyancy and wind-stress in driving the deep overturning. In the quest to fully understand the physics of the system one particular need is to improve the knowledge regarding the role of mechanisms that operate below the minimum scale resolved by the climate models. This project will use cutting-edge three-dimensional direct numerical simulations (DNS) to analyse a closed basin circulation forced by both wind and buoyancy, which will be dynamically similar to the North Atlantic circulation. We can now build on these insights for buoyancy-driven circulation and apply surface wind stress, to examine the relative roles of both the factors on gyre circulations. This imposes Ekman transport and vertical Ekman pumping on the convective circulation and introduces Rossby wave propagation and intensification of western boundary currents. This proposed work will provide many new insights, including new scaling results for boundary layer thickness and heat transport, and a large role of irreversible mixing of the density field. Thus, for the first time, the classic dynamics of a wind-driven ocean will be coupled to those of high-Rayleigh-number turbulent convective circulation.