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Earlier lectures

October 2020

Dynamics Of The Spatio-Temporal Wave-Front As Unique Precursor Of Flow Transition

Speaker: Dr. Swagata Bhaumik

Date & time: 31st Oct 2020 @ 11:00 am (New Delhi)
30th Oct: 10:30 pm (Los Angeles); 31st Oct 2020 @ 6:30 am (Berlin), 1:30 pm (Beijing), 2:30 pm (Tokyo)

Abstract of the lecture

Regardless of numerous theoretical, numerical and experimental efforts, several aspects of laminar to turbulent transition in fluid flows still remain ambiguous. One way of studying the flow transition is by treating it as a dynamical system where transition is caused by amplification of instability waves, which are mathematically, posed as the eigen-solution of the linearized governing equations describing evolution of small disturbances over the base flow. Instability waves are triggered inside the boundary layer by natural or imposed external perturbations through a process known as receptivity, a term receptivity first coined by Morkovin (Springer, 1993). Conventionally flow instability is studied by treating it either as temporal or spatial problem disregarding the spatio-temporal evolution of physical disturbances. Linearized spatio-temporal analysis of incompressible boundary layer by Bromwich contour integral method predicted the existence of the spatio-temporal wave-packet (STWP) (Sengupta et al. Phys. Rev. Lett., 96, 2006), which exhibits growth even for flows, which are stable following linearized stability analysis. Subsequently, the STWP has been established as the prime-mover for flow transition by high-accuracy direct numerical simulation (DNS) of the receptivity of the low-speed incompressible flows [1-6] to monochromatic definitive wall-excitation (started impulsively or gradually). These showed how STWP triggers flow transition and generation of turbulent spots, which later merge together to create fully developed turbulent flow. 3D receptivity results reported in [5,6] showed that both K- and H- route of flow transition can be induces by the growth of STWP due to single monochromatic excitation frequency.

Related publications

  1. T. K. Sengupta, S. Bhaumik, Onset of turbulence from the receptivity stage of fluid flows, Physical Review Letters 107(15) (2011) 154501.
  2. T. K. Sengupta, S. Bhaumik, Y. G. Bhumkar, Direct numerical simulation of two-dimensional wall-bounded turbulent flows from receptivity stage, Physical Review E 85(2) (2012) 026308.
  3. S. Bhaumik, T. K. Sengupta, Precursor of transition to turbulence: Spatiotemporal wave front, Physical Review E 89(4) (2014) 043018.
  4. S. Bhaumik, T. K. Sengupta, A new velocity-vorticity formulation for direct numerical simulation of 3D transitional and turbulent flows, Journal of Computational Physics 284 (2015) 230–260.
  5. P. Sharma, T. K. Sengupta, S. Bhaumik, Three-dimensional transition of zero-pressure-gradient boundary layer by impulsively and nonimpulsively started harmonic wall excitation, Physical Review E 98 (2018) 053106.
  6. S. Bhaumik, T. K. Sengupta, Z. A. Shabab, Receptivity to harmonic excitation following nonimpulsive start for boundary-layer flows, AIAA Journal (2017) 3233–3238.

Pointwise contact numerical models and applications

Speaker: Prof. Alfredo G Neto

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Watch lecture on Youtube https://www.youtube.com/watch?v=3VpkVH2osxk

Abstract of the lecture

In this lecture an overview of computational modeling of pointwise contact will be given. Beam-to-beam contact will be addressed, such as contact involving rigid/flexible bodies, modeled by beams/shells. An overview of the master-master contact strategy will be provided, presenting its pros/cons, such as numerous examples.

Related publications

  1. Gay Neto, A.; Wriggers, P.; Master-master frictional contact and applications for beam-shell interaction. Computational Mechanics, Published Online, 2020.
  2. Gay Neto, A.; Wriggers, P.; Numerical method for solution of pointwise contact between surfaces. Computer Methods in Applied Mechanics and Engineering, v. 365,112971, 2020.
  3. Gay Neto, A.; Wriggers, P.; Computing pointwise contact between bodies: a class of formulations based on master-master approach. Computational Mechanics, Published Online, 2019.
  4. Campos, P.R.R.; Gay Neto, A.; Rigid body formulation in a finite element context with contact interaction. Computational Mechanics, 62:1369, 2018.
  5. Gay Neto, A.; Pimenta, P. M.; Wriggers, P.; Contact between spheres and general surfaces. Computer Methods in Applied Mechanics and Engineering, v. 328, p. 686-716, 2018.
  6. Gay Neto, A.; Campello, E. M. B.; Granular materials interacting with thin flexible rods. Computational Particle Mechanics, v. 4, p. 229-247, 2017.
  7. Gay Neto, A.; Pimento, P. M.; Wriggers, P.; A master-surface to master-surface formulation for beam to beam contact. Part II: Frictional interaction. Computer 8. Methods in Applied Mechanics and Engineering, v. 319, p. 146-174, 2017.
  8. Gay Neto, A.; Simulation of mechanisms modeled by geometrically-exact beams using Rodrigues rotation parameters. Computational Mechanics, v. 59, p. 459-481, 2017.
  9. Gay Neto, A.; Pimento, P. M.; Wriggers, P.; A master-surface to master-surface formulation for beam to beam contact. Part I: Frictionless interaction. Computer Methods in Applied Mechanics and Engineering, v. 303, p. 400–429, 2016.

Computational fluid-structure interaction – large deformations, added-mass and staggered schemes

Speaker: Dr. Chennakesava Kadapa

Abstract of the lecture

Computational fluid-structure interaction quickly becomes a challenging endeavour for problems involving complex geometries, large structural deformations, topological changes and thin lightweight structures. Conventional CFD solvers based on body-fitted meshes become practically useless for problems undergoing large structural deformations, and the fully-coupled approaches for FSI are not only expensive but also limit the extent of coupling of different fluid and solid solvers. The alternatives, however, are not without their shortcomings. In this talk, I present a state-of-the-art simulation framework for FSI that can successively and efficiently overcome many of the challenges frequently encountered in simulating challenging FSI problems.

Shaping the future of A/C structural integrity assessment using smarter testing and simulation

Speaker: Mr. Jaya Raju Namala

Abstract of the lecture

The lecture will focus on nonlinear structural modeling of aircraft structures. The emphasis will particularly be on the evolution of advanced nonlinear simulations usage at Airbus, Success stories and current state of the art, future vision, challenges and way forward. The intended audience for the talk includes structural simulation practitioners, university students (Masters and above) and researchers in the field of structural mechanics.

September 2020

Introduction to and applications of Synchronization theory

Speaker: Prof. Sirshendu Mondal

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Download lecture from Youtube Coming soon

Abstract of the lecture

In nature, oscillations are one of the main forms of motion and these oscillating systems are not isolated. So, they interact, communicate in different kinds of complex ways. With this, synchronization is the most fundamental phenomenon exhibited by these systems. In the first part this talk, the basics of synchronization theory will be discussed. Applications of synchronization theory will be demonstrated in different engineering and natural systems, in the second part of my lecture. The engineering systems include thermoacoustic system, aeroelastic system, and natural circulation loop. Through these applications, we will discuss how synchronization theory helps not only describing different transitional phenomena but also indicating the possible control measures.

Related publications

  1. Mondal, S., Unni, V. R., & Sujith, R. I. (2017). Onset of thermoacoustic instability in turbulent combustors: an emergence of synchronized periodicity through formation of chimera-like states. Journal of Fluid Mechanics, 811, 659.
  2. Mondal, S., Pawar, S. A., & Sujith, R. I. (2017). Synchronous behaviour of two interacting oscillatory systems undergoing quasiperiodic route to chaos. Chaos: An Interdisciplinary Journal of Nonlinear Science, 27(10), 103119.
  3. Thomas, N., Mondal, S., Pawar, S. A., & Sujith, R. I. (2018). Effect of time-delay and dissipative coupling on amplitude death in coupled thermoacoustic oscillators. Chaos: An Interdisciplinary Journal of Nonlinear Science, 28(3), 033119.
  4. Dange, S., Manoj, K., Banerjee, S., Pawar, S. A., Mondal, S., & Sujith, R. I. (2019). Oscillation quenching and phase-flip bifurcation in coupled thermoacoustic systems. Chaos: An Interdisciplinary Journal of Nonlinear Science, 29(9), 093135.
  5. Raaj, A., Venkatramani, J., & Mondal, S. (2019). Synchronization of pitch and plunge motions during intermittency route to aeroelastic flutter. Chaos: An Interdisciplinary Journal of Nonlinear Science, 29(4), 043129.
  6. Mondal, S., Pawar, S. A., & Sujith, R. I. (2019). Forced synchronization and asynchronous quenching of periodic oscillations in a thermoacoustic system. Journal of Fluid Mechanics, 864, 73-96.
  7. Roy, A., Mondal, S., Pawar, S. A., & Sujith, R. I. (2020). On the mechanism of open-loop control of thermoacoustic instability in a laminar premixed combustor. Journal of Fluid Mechanics, 884.

Novel developments in clamped geometries for fracture toughness testing

Speaker: Prof. Nagamani Jaya Balila

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Abstract of the lecture

Stable fracture toughness test geometries are useful in not only determining the monotonic fracture toughness, but also in capturing the R-curve behaviour and damage tolerance of materials under cyclic loading and extreme environments. The doubly clamped boundary condition offers such crack stability even in the most brittle materials. This talk will cover all aspects of clamped beams and wires in tension and bending as fracture toughness test geometries including their geometric factor solutions for linear elastic and elastic-plastic cases. Finite element simulations are used to explain the mechanics of crack stability for various beam and wire aspect ratios and crack configurations. Their varied applications in bulk materials, architectured systems, thin film multilayers and graded coatings will be shown.

Related publications

  1. A. K. Mishra, A. Lambai and V. Jayaram, B. Nagamani Jaya, “The edge-notched clamped beam bend specimen as a fracture toughness test geometry”, Theoretical and Applied Fracture Mechanics, 105, 2020, 102409 (DOI: 10.1016/j.tafmec.2019.102409)
  2. B. Nagamani Jaya, Sanjit Bhowmick, S. A. Syed Asif, Oden L. Warren and Vikram Jayaram, “Optimization of clamped beam geometry for fracture toughness testing of micron-scale samples” Phil Mag Special Issue on Nanomech IV, Vol 95, 2015, 1945-1966 (DOI: 10.1080/14786435.2015.1010623)
  3. B. Nagamani Jaya and Vikram Jayaram, “Crack stability in edge notched clamped beam specimen under bending: modeling and experiments”, International Journal of Fracture, Vol 188, Issue 2, 2014, 213-228 (DOI: 10.1007/s10704-014-9956-2)
  4. B. Nagamani Jaya, Vikram Jayaram and Sanjay K. Biswas, “A new method for fracture toughness determination of graded (Pt,Ni)Al bond coats by microbeam bend tests”, Philosophical Magazine Special Issue on Nanomechanical Testing in Materials Research and Development III, Vol 92, Issue 25-27, 2012, 3326-3345. (DOI: 10.1080/14786435.2012.669068)

Fascinating flows in simple and enigmatic marine animals

Speaker: Prof. Vivek N Prakash

Abstract of the lecture

Animals are characterized by their movement, and their tissues are continuously subjected to dynamic force loading. Tissue mechanics determines the ecological niches that can be endured by a living organism. In the first part of my talk, I will present our surprising discovery of motility-induced tissue fractures and healing in a simple, early divergent marine animal - the Trichoplax adhaerens. I will demonstrate how fracture mechanics governs dramatic shape changes and asexual reproduction in this animal. In the second part of my talk, I will focus on the role of fluid mechanics in marine invertebrates. Many marine invertebrates have larval stages covered in linear arrays of beating cilia, which propel the animal while simultaneously entraining prey. In starfish larvae, we discovered that these ciliary arrays give rise to a beautiful pattern of slowly evolving vortices. I will elucidate how these vortices create a physical tradeoff between feeding and swimming in heterogeneous environments. For more information, please visit: Prakash Lab at Miami.


August 2020

Chaotic footprints of a flapping wing: A computational perspective

Speaker: Dr. Chandan Bose

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Abstract of the lecture

The lecture will discuss the investigations made on the complex vortex interactions in a flapping wing. The flow-field transitions from periodic to chaotic through a quasi-periodic route as the plunge amplitude is gradually increased. This study unravels the role of the complex interactions that take place among the main vortex structures in making the unsteady flow-field transition from periodicity to chaos.

Machine intelligence in mechanical and aerospace sciences: Today & beyond

Speaker: Dr. Rajnish Mallick

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Abstract of the lecture

AI and ML have been topics of huge interest in the recent times. Machine learning techniques are being applied vastly to understand the uncertainities in the models - both solid and fluid mechanics. During the lecture, we will discuss on how artificial intelligence is being in used in the aerospace industry.

Homogenization of heterogeneous materials for aerospace applications

Speaker: Prof. Guruprasad P J

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Abstract of the lecture

Micromechanical analysis of heterogeneous can be effectively carried out using the variational asymptotic method (VAM) unit cell homogenization technique. The governing equations obtained by adopting this technique can be solved using numerical methods by conformal discretization of the domain. In the case of heterogeneous materials, conformal discretization of the domain becomes difficult and time-consuming. It is preferable to have a non-conformal discretization procedure for problems involving complex geometries, for example, woven composites. A novel numerical framework for the micromechanical analysis of heterogeneous materials based on VAM is proposed, where the level-set method is used to define the interface as well as to decompose the domain into voxel regions of inclusions and matrix. The point interpolation method (PIM) is used to connect these voxel regions. The PIM-VOXEL framework thus developed is validated using examples having complex geometries taken from open literature for predicting elastic, thermal, thermo-elastic, and visco-elastic properties. The proposed methodology alleviates the requirement for conformal meshing without compromising the accuracy and is capable of automation for homogenization and localization applications. Finally, the application of the numerical framework to capture damage initiation and progression in woven composites is demonstrated.

Related publications

  • Rajeev, G. N., Sundararajan, T., B. and Guruprasad, P. J., 2018. A novel framework using point interpolation method with voxels for variational asymptotic method unit cell homogenization of woven composites. Composite Structures, 202: 261-274 (Link)

  • Pandi, P. Berger, H. and Guruprasad, P. J., 2020. Investigating the influence of interface in a three phase composite using variational asymptotic method based homogenization technique. Composite Structures, 233: 111562 (Link)

  • Pandi, P. and Guruprasad, P. J., 2020. Determination of the influence of interfacial thermal resistance in a three phase composite using variational asymptotic based homogenization method. International Journal of Heat and Mass Transfer, 155: 119889 (Link)


July 2020

Inspirations and equations derived from VAM for mechanics of student life

Speaker: Prof. Dineshkumar Harursampath

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Abstract of the lecture

The lecture will discuss various aspects of modeling in aerospace structures. In particular, the lecture will focus on the modeling of composite materials using the Variational Asymptotic Method (VAM).

Related publications

  • D. Harursampath, Introduction to the Special Section on Asymptotic Analyses, Dynamics and Aeroelasticity, AIAA Journal, Vol. 57 (10), 2019, pp. 4118-19 (Link)

  • D. Harursampath, A. B. Harish and D. H. Hodges, Model Reduction in Thin-Walled Open-Section Composite Beams using Variational Asymptotic Method. Part II: Applications, Thin-Walled Structures, 117, 2017, pp. 367-77 (Link)


UEL in Abaqus

Speaker: Dr. Niraj K Jha

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Abstract of the lecture Dr. Jha will present a methodology for the development of UEL in Abaqus CAE. In this regard, the lecture will focus on modeling of the constitutive behavior of hyperelastic materials. In addition, the lecture will also demonstrate the development of cohesive elements as well. Over the course of the lecture, he will present theoretical formulations followed by code review. The intended audience of this lecture is Master / Ph.D. / Industry participants who are beginning to use UEL routines in Abaqus CAE.