Dr. Srikanth Toppaladoddi

University of Oxford
United Kingdom

Mobirise

19th Seminar: October 23, 2020

Nonlinear interactions between fluid flows and evolving boundaries

Abstract
Interactions between fluid flows and evolving boundaries are at the heart of some of the most challenging problems in applied mathematics, geophysics, climate physics, and engineering. In this talk, I will explore the interplay between shear- and buoyancy-driven flows and a phase-changing boundary using linear stability analysis and direct numerical simulations. Specifically, I will consider Rayleigh-Benard-Couette and Rayleigh-Benard-Poiseuille flows of a pure liquid phase under its solid phase - which can either melt or freeze - to understand the impact of these interactions on the evolution of the solid phase and the heat transport in the liquid phase.


Publications

Prof Woosok Moon

Department of Mathematics & NORDITA
Stockholm University, Sweden

Mobirise

18th Seminar: September 24, 2020

Dancing with fluctuations in seasonal climate

Abstract
Earth’s orbit and axial tilt imprint a strong seasonal cycle on climatological data. Climate variability is typically viewed in terms of fluctuations in the seasonal cycle induced by higher frequency processes. We can interpret this as a competition between the orbitally enforced monthly stability and the fluctuations/noise induced by weather. Here we introduce a new time-series method that determines these contributions from monthly-averaged data. We find that the spatio-temporal distribution of the monthly stability and the magnitude of the noise reveal key fingerp rints of several important climate phenomena, including the evolution of the Arctic sea ice cover, the El Nio Southern Oscillation (ENSO), the Atlantic Nio and the Indian Dipole Mode. In analogy with the classical destabilising influence of the ice-albedo feedback on summertime sea ice, we find that during some time interval of the season a destabilising process operates in all of these climate phenomena. The interaction between the destabilisation and the accumulation of noise, which we term the memory effect, underlies phase locking to the seasonal cycle and the statistical nature of seasonal predictability.



Publications

Prof Grzegorz Litak

Department of Applied Mechanics
Lublin University of Technology, Poland

Mobirise

17th Seminar: February 4, 2020

Wind energy harvesting by vortex-induced vibrations and galloping

Abstract
Energy harvesting performance of a piezoelectric wind energy scavenger are discussed. Particularly, we consider different cross-sectioned bluff bodies to enhance the performance by coupling both the vortex-induced vibrations and galloping phenomena. Theoretical, experimental and computational fluid dynamics studies are conducted to investigate the harvesting performance with three different combinations of the circular and square cross sections corresponding to the different values of a attack angle. Both theoretical analysis and experimental results reveal that the aerodynamic coefficients (Strouhal number and galloping force coefficients) play key roles in the energy scavenging characteristics.


Publications

Dr. Mahesh Kumar Sha

Royal Belgian Institute of Space Aeronomy,
Belgium

Mobirise

16th Seminar: January 30, 2020

Ground-based remote sensing measurements of greenhouse gases in Earth's atmosphere and its relevance to global warming

Abstract
Remote sensing techniques play a significant role for probing the greenhouse gas (GHG) cycles in the Earth’s atmosphere. Anthropogenic greenhouse gas emissions has been on a continuous rise since the industrialization began with considerably high increase rates in the recent years. Accurate and precise measurements of the GHGs are of importance to estimate their emission strengths, flux changes and long term monitoring. The measurements will be of direct relevance for the verification of climate mitigation actions as demanded by the COP21 Paris agreement. Satellites provide a global coverage of these species. However, they are susceptible to biases and drifts with time. Ground-based accurate and precise remote sensing measurements of these gases are therefore needed for the calibration and validation of the satellite data. This talk will focus on the solar absorption measurement techniques used for the study of sources and sinks of greenhouse gases thereby entangling the issue of global warming, which is one of the major concerns for the survival on Earth. The talk will address the existing ground-based infrared remote sensing greenhouse gas observation networks and their use for the validation of models and greenhouse gas measurements from satellites.


Publications

Complex Systems & Dynamics     Indian Institute of Technology Madras     Chennai 600036     India