With rapid developments in the technology of aerial vehicle and under-sea exploration, the study of wakes has become crucial for understanding vehicle dynamics and their environmental impact. Since the atmosphere and the ocean are often stratified with heavy underneath light fluid, wakes in the natural environment exhibit fascinating physics induced by density variation.
In this project, high-fidelity LES (Large Eddy Simulations) are performed for a 6:1 prolate spheroid at moderate 10-degree angle of attack. Effects of both stratified and unstratified medium on wake dynamics and turbulence statistics are studied for varying Reynolds Number ~ 5,000 to 30,000. Primary focus of our work is studying evolution of streamwise vortex pair generated from flow separation, SPOD (Spectral Proper Orthogonal Decomposition) of the flow field to gain insights into the vortex shedding modes and effects of stratification on Turbulence Kinetic Energy budget.
Preliminary results were published in the 2024 TSFP13 conference proceeding held at Montreal, Canada and 2024 SNH35 conference proceeding held at Nantes, France.
Rapid imaging of individual biological cells in a large population can be used as an effective method for clinical testing of various diseases like malaria and cancer. In this work, we completed design, characterization, and testing of an inexpensive, sheath-flow based microfluidic device for three-dimensional (3D) hydrodynamic focusing of cells in imaging flow cytometry.
Extensive numerical simulations of the microfluidic channels were performed on COMSOL to optimize the design and flow parameters. Subsequently, the microfluidic device was fabricated and experimental vaildation of the concept was done by 3D focusing RBCs and imaging them under a Digital Holographic Microscope. Our device hydrodynamically focuses the cells in a single-file near the bottom wall of the microchannel that allows imaging of cells with high magnification and low working distance objectives, without the need for small device dimensions.
Detailed results from this study were published in AIP Biomicrofluidics article: Yogesh Patel, Sanidhya Jain and Supreet Singh Bahga 2020.
Electrospray thruster is a novel electric propulsion system devised for attitude control in low-earth orbit micro and nano-satellites. These thrusters, unlike traditional chemical rocket propulsion systems, have a very high specific impulse. Therefore, it provides more precise thrust control with less propellent mass, enabling longer lifespan for same amount of propellent.
A hybrid study consisting of two different simulations was performed. Firstly, multiphase flow simulations for EHD (Electrohydrodynamic) jet were performed for varying thruster geometry and extractor voltage. Results obtained from these simulations (eg, droplet size, charge density, etc.) were then fed into the Lagrangian solver to compute trajectories of charged droplets in the electrospray by solving n-body problem. Design and control parameters were optimized for maximum thruster efficiency.
In collaboration with Indian Space Research Organization (ISRO)