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A Study on Fluid Flow, Heat Transfer, and Scaling Laws   of Breeder Blanket Concept of Fusion Reactor 

22 Mar 2024 | Bernoulli, ME Department

Seminar of Taaresh Taneja (PhD student, University of Minnesota) on Non-Equilibrium Plasma and its Use in Combustion: A Modeling Perspective

Abstract:

Non-equilibrium or Low Temperature Plasma is a state of a gas which is characterized by a
difference in the energies of the electrons and other heavy species of the gas. Such a plasma
typically constitutes of gas molecules, a relatively lower density of ions and rotational, vibra6onal, and electronic excited states, neutral radicals, along with free electrons. Non-equilibrium plasmas can exist at various gas pressures ranging from 0.1 – 106 Pa and gas temperatures, ranging from 100 – 10000 K. Across these wide range of conditions, the physical and chemical properties of the plasma can vary substantially – which make them extremely useful in diverse technological areas such as semiconductor manufacturing, water treatment, medical equipment sterilization, nanomaterial synthesis, chemical reforming, combustion assistance, etc. Between 104 - 106 Pa and 300 – 5000 K, these non-equilibrium plasma discharges can be used for assis6ng combustion. This assistance is provided majorly through two channels – gas hea6ng and chemical radical production. Both these channels can be used to ignite renewable and carbon-free fuels such as ammonia (NH!), which is very difficult to burn, and stabilize flames in challenging conditions such as gas turbines, scramjet, and rocket combustors. Moreover, the chemical pathways introduced by the non-equilibrium of the gas, can also help to lower, or completely prevent emissions from combustion, such as unburned hydrocarbons, soot, CO2, CO and NOx. High fidelity computational simulations (DNS / LES) of non-equilibrium "plasma assisted combuston" (PAC) face various constraints due to the wide- ranging temporal (10-15 – 10-2 s) and spa6al (10-6 – 10-1 m) scales of this problem, which make the system of governing equations very s6ff. Furthermore, the highly coupled interaction of electrostatics, plasma chemistry, combustion chemistry, and turbulent flow renders PAC its mul6-physics nature. This talk will provide an overview of the governing physics, the mathematical formulation of different models, and a few technological applications of non-equilibrium plasma assisted combustion.

 

 

 

Brief Bio-data of speaker:
Taaresh Taneja is a 5th year PhD candidate at the University of Minnesota (UMN), Twin Ci>es,
who is currently focused on modeling non-equilibrium plasma assisted combus>on. He works
with Prof. Suo Yang, in the Computa>onal Reac>ve Flow and Energy Laboratory (CRFEL) at UMN.
For his research, he has received the UMII MNDrive Fellowship, NSF Supplemental Funding
Opportunity and the UMN Doctoral Disserta>on Fellowship, along with other travel grants for
presen>ng his work at conferences. Taaresh has also interned at the Na>onal Renewable Energy
Laboratory, Colorado and at Sandia Na>onal Laboratory, California during his PhD. Before joining
UMN for his PhD in 2019, Taaresh worked as a CFD engineer at Johnson Controls India Pvt. Ltd.,
Pune (2017 - 2019). He received his B.E. (Hons) in Mechanical Engineering from BITS Pilani, Goa
Campus in 2017.

 

 

 

13 Mar 2024 | ME Dept Auditorium

Prof. Shyamprasad Karagadde has been awarded the Faculty Award for Research Excellence (FARE) instituted by the class of 1973 on the occasion of Golden Jubilee.

12 Feb 2024 |

PhD viva-voce examination of Ritesh Dadhich 
Title of the thesis: Development of a spectral solver for crystal plasticity

Chairman : Prof. Chandra S. Yerramalli, Department of Aerospace Engineering, IIT Bombay
External Examiner : Prof. Anoop Krishnan, Department of Applied Mechanics, IIT Delhi
Internal Examiner : Prof. Tanmay K. Bhandakkar, Department of Mechanical Engineering, IIT Bombay
Supervisor : Prof. Alankar Alankar, Department of Mechanical Engineering, IIT Bombay

08 Feb 2024 | ME Dept Auditorium

Ph.D. defence of Amir Hamza Siddiqui on Novel cruciform specimen design and plastic flow behaviour of anisotropic material under in-plane biaxial loading

Chairman: Prof. Chandrasekher Yerramalli (Dept of Aerospace Engg, IIT Bombay)
External Examiner: Prof. D. Ravi Kumar (Dept of Mechanical Engg, IIT Delhi)
Internal Examiner: Prof. Sushil Mishra (Dept of Mechanical Engg, IITB)
Supervisor: Prof. Anirban Guha
Co-supervisor: Prof. Asim Tewari
 

01 Feb 2024 | Room F24, Mechanical Department

Ph.D. defense of Mr. Harish Veeravenkata on Ab-initio Modelling of Materials for Energy Applications

Abstract: 
The aim of this thesis is to examine thermal transport in semiconductors. In crystalline semiconductors, phonons (atomic vibrations) play a crucial role in thermal transport, whereas in metals, electrons are the primary carriers of both heat and charge.

To predict the properties of phonon and electron transport, we employ first-principles calculations. This involves considering various scattering mechanisms such as phonon-phonon, phonon-boundary, and phonon-isotope interactions, and utilizing the Boltzmann transport equation. The scattering rates associated with phonon-phonon interactions are determined by conducting calculations based on both harmonic and anharmonic lattice dynamics. In order to perform these calculations, we obtain harmonic and cubic force constants, which are necessary inputs, through density functional theory and density functional perturbation theory calculations.
The thermal transport properties of biphenylene network (BPN), a novel sp2-hybridized two-dimensional allotrope of carbon atoms recently realized in experiments, are studied using the density functional theory-driven solution of the Boltzmann transport equation. The thermal transport in BPN is anisotropic and the obtained thermal conductivities are more than an or-
der of magnitude lower than that in graphene, despite similar sp2-hybridized planar-structure of both allotropes. The lower thermal conductivity in BPN is found to originate from enhanced anharmonicity which in turn is a result of reduced crystal symmetry of BPN.

The thermal transport properties of the recently synthesized high-pressure phase of BNC2 are investigated using the iterative solution of the Boltzmann transport equation with inputs from density functional theory calculations. The thermal conductivity of BNC2 is found to be extremely sensitive to pressure, and the thermal conductivity at room temperature under 20 GPa pressure is over 1400 W/m-K which is more than 40% higher than the cor- responding value at 0 GPa. Similar to diamond, the origin of this extremely high thermal conductivity is rooted at large phonon group velocities, which gives rise to fluid-like hydrodynamic thermal transport in BNC2. However, unlike diamond, the large isotope disorder of boron atoms in BNC2 results in a large phonon-isotope scattering, which renders hydrodynamic flow prevalent only in isotopically pure samples at length scales of up to 65 μm at 100 K.
 

Date: 1 Feb 2024
Time: 4 PM
Venue: ME Auditorium 

External Examiner: Prof. Abhishek Singh, IISc
Internal Examiner: Prof. Amit Singh
Chairperson: Prof. Aftab Alam, Physics 

Supervisor: Prof. Ankit Jain

01 Feb 2024 | ME Auditorium

PhD defense of Mr. Vishwas Divse on Progressive Damage Modeling of Fiber Reinforced Plastic Composites including Drilling-induced Damage 

Abstract:
Fiber-reinforced plastic (FRP) composite laminates are extensively used in aerospace structures for their high specific strength and stiffness. However, the presence of holes for assembly and drilling-induced damage significantly weakens the laminates, leading to premature failure due to stress concentration. Designers and engineers currently lack a comprehensive understanding of damage propagation and limiting strength in FRP laminates with holes and drilling-induced damage. As a result, components made of FRP laminates are often over-designed. To address this issue, the development of reliable progressive damage models (PDMs) that accurately capture damage propagation in FRP laminates has become a critical research focus for the past three decades.

This study focuses on the development of mesoscale progressive damage models (PDMs) based on continuum damage mechanics, incorporating well-established failure criteria such as 2D Hashin, 3D Hashin, Puck, and LaRC05. These PDMs take into account various damage modes, including matrix cracking, matrix crushing, ber breakage, and fiber kinking. Additionally, they incorporate shear non-linearity, in-situ strengths, and mixed mode fracture and employ a numerical search algorithm to determine the kink-band plane and matrix fracture angles. The PDMs were implemented within the Abaqus/explicit finite element framework using the VUMAT subroutines written in FORTRAN. Specifically, finite element method (FEM) based models were employed to de ne pre-existing ber or matrix damage in the subroutines. The PDMs were first verified with single-element and mesh dependency tests. Furthermore, FEM-based models were developed to simulate open-hole tension (OHT) and open-hole compression (OHC) tests that aim at predicting damage propagation and the corresponding limiting strength of the FRP laminates. Lastly, both FEM-based simulations and experiments were conducted to analyze drilling-induced damage and its impact on the OHT strength of FRP laminates.

The study reveals that the stress concentration factor (SCF) substantially increases with an increase in hole size. Interestingly, laminates can be designed with SCF (<3) lower than an open hole in a finite isotropic plate by suitable stacking of on- and off-axis plies. When subjected to tension, an open hole lamina always fails due to matrix cracking along the ber direction. However, laminates demonstrate complex failure interactions involving multiple damage mechanisms. During OHT tests, ply-blocked laminates show around 30% higher strength and fracture strain than non-ply-blocked laminates due to delayed damage propagation. The ply-blocked laminates display reduced sensitivity to hole size, resulting in a 14.3% reduction in OHT strength when the hole size increases from 6 to 9 mm, compared to a 21.14% reduction in the non-ply-blocked laminates. In OHC tests, ber splitting and kinking initiate at regions of maximum in-plane shear stress and propagate due to longitudinal compression and in-plane shear stress. The ultimate failure of 0 degree dominant and quasi-isotropic layup is governed by ber kinking in 0 degree plies, while matrix cracking and delamination in 45 degrees plies contribute to the nal failure of shear dominant layups. Notably, the quasi-isotropic layup was observed to be more sensitive to hole (or notch) size than the other laminates.

Furthermore, it was found that drilling-induced damage increases with feed rate and drill-bit size, while cutting speed has a slight mitigating effect. Drilling-induced damage predominantly propagates along the ber orientation of the exit ply in the laminate. The digital image correlation (DIC) analysis shows heightened strain concentration at the location of drilling-induced damage, resulting in accelerated damage propagation and reduced overall laminate strength. This leads to up to a 15% decrease in open-hole tension (OHT) strength and a 7-11% decrease in open-hole compression (OHC) strength. Drilled laminates experience a significant strength reduction of up to 50% compared to plain laminates due to the combined effect of the hole and drilling-induced damage. Therefore, designing FRP laminates with holes and pre-existing damage requires careful consideration. The proposed models show predictions within a 10-15% deviation from experimental results for OHT tests, OHC tests, and drilling. These models hold the potential for solving engineering problems, especially when extended to account for cyclic loading scenarios.

External Examiner: Prof. Naresh Bhatnagar, IIT Delhi
Internal Examiner: Prof. Dnyanesh Pawaskar 
Chairperson: Prof. Krishna Kaliappan, Chemistry 
 
Supervisor: Prof. Deepak Marla
Co-Supervisor: Prof. Suhas Joshi 

31 Jan 2024 | ME Auditorium

Final PhD viva-voce examination of Mr. Ritam Chatterjee

Title of the thesis: Development of Mean-Field and Full-Field Crystal Plasticity Phase-Field Models to Investigate Dynamic Recrystallization

Date: Wednesday, Jan 31, 2024
Time: 9:00 AM
Venue: Bernoulli Meeting Room

Details of the examination panel are as follows:

Chairperson: Prof. Alok Shukla, IIT Bombay
External Examiner: Prof. Amit Arora, IIT Gandhinagar
Internal Examiner: Prof. Tanmay Bhandakkar, IIT Bombay
Thesis Supervisor:  Prof. Alankar, IIT Bombay

31 Jan 2024 | Bernouli

Prof. Prasanna Gandhi honoured in recognition of his contribution to ISRO's first moon landing mission.

https://www.news9live.com/science/iit-bombay-receives-chandrayaan-3-honor-in-recognition-of-contribution-to-isros-first-moon-landing-2327578

19 Jan 2024 |

Talk by Prof. G. C. Nandi, Dean (Acad) and Head of the Department, Dept. of Information Technology, IIIT Allahabad, on Language Conditioned Human Robot Interactions as per the following schedule today

Time: 4:00 PM Venue:  ME Dept Auditorium

Abstract:

The pursuit of creating robots that seamlessly comprehend and execute natural language directives has remained a longstanding aspiration within the realm of artificial intelligence. While the burgeoning advancements in generative AI and Large Language Models (LLMs) have catalyzed recent explorations in this domain, hardly any endeavors have successfully materialized a tangible embodiment of such technology. These exceptional instances involve robots that operate within our physical world, proficiently responding to a vast spectrum of intricate linguistic commands. The primary impediment to achieving this ambitious goal lies in the intricacy of commanding a robot to identify and manipulate objects within an unfamiliar environment, relocating them to a prescribed destination. This task poses an immense challenge for robots striving to serve as valuable aides in human-centric settings, as it necessitates the mastery of multiple facets spanning the diverse spectrum of robotics disciplines. Conquering this challenge mandates adeptness in perception, language comprehension, navigation, and dexterous grasp manipulation. Within the context of this discourse, the present talk will elucidate some of the formidable challenges intrinsic to this pursuit and also shed light on the ongoing research endeavors undertaken by my team in the realm of intelligent grasp manipulation. Our objective is to harmonize the intricate symphony of human-robot interactions, bringing us closer to the realization of robots as versatile and discerning collaborators in our everyday lives.
 

17 Jan 2024 | ME Dept Auditorium

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