FY2016 Annual Report

Collective Interactions Unit
Assistant Professor Mahesh Bandi

Abstract

We are an experimental group with primary interests in nonlinear and non-equilibrium physics, both applied and fundamental. Our work often intersects with soft matter physics, applied mathematics, mechanics, and their application to biologically inspired problems. Our current focus is trained towards problems in interfacial fluid dynamics, granular solids, biomechanics of the human foot and fluctuations in renewable energy sources.

1. Staff

  • Mr. Osamu Horiguchi, Rotation Student
  • Dr. V. Sathish Akella, Postdoctoral Scholar
  • Dr. Florine Paraz, Postdoctoral Scholar
  • Dr. Harsha M. Paroor, Postdoctoral Scholar
  • Mr. Alexandru Mihai, Rotation Student
  • Ms. Ayano Sakiyama, Group Administrator
  • Dr. Dhiraj K. Singh, Postdoctoral Scholar
  • Mahesh M. Bandi, Assistant Professor

2. Collaborations

2.1 Foot in motion - materials, mechanics & control (funded by HFSP)

  • Description: Theoretical, numerical and experimental studies in evolution of stiffness in the human foot.
  • Type of collaboration: Joint research
  • Researchers:
    • Professor Madhusudhan Venkadesan, Yale University, USA.
    • Mr. Nihav Dhavale, National Centre for Biological Sciences, India.
    • Ms. Neelima Sharma, Yale University, USA.
    • Professor Shreyas Mandre, Brown University, USA.
    • Ms. Maria Fernanda Lugo-Bolanos, Brown University, USA.
    • Professor Mahesh M. Bandi, OIST Graduate University, Japan.
    • Dr. Dhiraj K. Singha, OIST Graduate University, Japan.
    • Mr. Khoi D. Nguyen, Technical Staff, OIST Graduate University, Japan.

2.2 Compaction in two-dimensional granular materials

  • Description: Compaction, disorder induced metastability, and convection in granular media..
  • Type of collaboration: Joint research
  • Researchers:
    • Professor Hiroaki Katsuragi, School of Environmental Sciences, Nagoya University.
    • Mr. Naoki Iikawa, School of Environmental Sciences, Nagoya University.
    • Professor Mahesh M. Bandi, OIST Graduate University, Japan.

2.3 Hydrodynamics of a self-propelled camphor boat

  • Description: The hydrodynamics and nonlinear dynamics of self-propelled camphor boats at air-water interfaces.
  • Type of collaboration: Joint research
  • Researchers:
    • Professor Shreyas Mandre, Brown University, USA.
    • Mr. Ravi S. Singh, Brown University, USA.
    • Professor Mahesh Bandi, OIST Graduate University, Japan.
    • Dr. V. Sathish Akella, OIST Graduate University, Japan.
    • Dr. Dhiraj K. Singh, OIST Graduate University, Japan.

3. Activities and Findings

3.1 Bird song prosody

Dr. Makoto Araki, Neuronal Mechanism for Critical Period Unit, OIST Graduate University.

Professor Yoko Yazaki-Sugiyama, Neuronal Mechanism for Critical Period Unit, OIST Graduate University

Mahesh M. Bandi, Collective Interactions Unit, OIST Graduate University.

Bird song prosody concerns emergence of species-specific learning from the basic features of bird song. Songbirds must simultaneously meet two competing demands: their song must be similar enough to one's own species, yet unique from that of other males within one's species to attract a mate. In a behavioral neuroscience experiment co-designed with my colleague Y. Yazaki-Sugiyama (OIST), we discovered a class of neurons in the Zebra finch auditory cortex, that register silent temporal gaps between song syllables, and were distinct from neurons encoding syllable morphology of the song. Combining behavioral experiments and electrophysiological measurements with information theory, we showed gaps between song syllables are genetically hardwired for inter-species discrimination, whereas song syllables learned from tutors provide the necessary intra-species diversity among songbirds. The experiments were conducted by Prof. Yazaki-Sugiyama's group with data analysis and theoretical contributions from our group.

3.2 Spectrum of Wind Power Fluctuations

Professor Mahesh M. Bandi, Collective Interactions Unit, OIST Graduate University, Japan

Wind Energy is a timely and relevant problem, where the fluid dynamics community's efforts have been primarily engaged towards improving individual turbine or collective plant efficiency. We have undertaken a critical analysis of wind power fluctuations. The power generated by a wind turbine fluctuates with varying wind speed and indeed, its spectrum reflects the Kolmogorov spectrum of atmospheric turbulence; both vary with fluctuation time scale τ as τ2/3 . This variability decreases when geographically distributed wind farms feed power to the grid and aggregate power fluctuations are averaged (geographic smoothing). Despite costs associated with variability, neither the τ2/3 wind power fluctuation scaling nor the geographic smoothing mechanism are understood. In this work, we have explained the wind power fluctuation spectrum from the turbine through grid scales. In particular, we theoretically deduced, and experimentally validated that the τ2/3 scaling of wind power fluctuations results from the largest length scales of atmospheric turbulence (~100s of km) influencing the small scales where individual turbines operate. This long-range influence correlates geographically distributed wind farm power outputs over a range of time scales that falls with the inter-farm distance. Consequently, we deduced that aggregate grid-scale power fluctuations smooth until they reach a limiting τ4/3 spectrum, and showed that regional grids have already hit this spectral bound. Through this theoretical framework it becomes possible to tackle several engineering and policy questions in renewable energy such as what are the fluctuation magnitudes that grid operators must account for in the design of smartgrids, or what are the back up storage options one must plan for to further smooth out fluctuations etc.

4. Publications

4.1 Journals

  1. Araki, M., Bandi, M. M., Yazaki-Sugiyama, Y. (2016). Mind the Gap: Neural coding of species identity in birdsong prosody. Science, 354(6317), 1282-1287. doi:http://dx.doi.org/10.1126/science.aah6799
  2. Das, T., Lookman, T., Bandi, M. M. (2016). Morphology dictated heterogeneous dynamics in two-dimensional aggregates. Soft Matter, 12, 9674-9682. doi:http://dx.doi.org/10.1039/c6sm02239a
  3. Mahesh M. Bandi and Jay Apt, "Variability of the Wind Turbine Power Curve, Appl. Sci.6, 262 (2016).
  4. N. Iikawa, M. M. Bandi, and H. Katsuragi, "Sensivity of Granular Force Chain Orientation to Disorder-induced Metastable Relaxation", Phys. Rev. Lett.116, 128001 (2016).
  5. G. Bel, C. P. Connaughton, M. Toots, and MM Bandi, "Grid-scale fluctuations and forecast error in wind power, "New J. Phys.18, 023015 (2016).

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

  1. Akella, V. S., Singh, D. K., Singh, R. S., Mandre, S., Bandi, M. M. (2016, 2016.12.12). Dynamics of a camphoric acid boat at the air-water interface, Hyderabad, India.
  2. Bandi, M. M. (2016). (Hydro)Dynamics of self-propelled camphor boats. Paper presented at the Micro and Macro scale flows in Soft Matter, OIST Graduate University, Japan.
  3. Bandi, M. M. (2016). Self-propelled Active Matter. Paper presented at the Hands-On Research in Complex Systems 2016, International Centre for Theoretical Physics, Trieste, Italy.
  4. Bandi, M. M. (2016, 2016.07.21). The Spectrum of Wind Power Fluctuations. Paper presented at the Statphys 2016, Lyon, France.
  5. Bandi, M. M. (2016, 2016.11.21). Spectrum of wind power fluctuations, Portland, Oregon, USA.
  6. Bandi, M. M., Akella, V. S. (2016, 2016.12.13). The Granular Pebble Game, Hyderabad, India.
  7. Bandi, M. M., Akella, V. S., Singh, D. K. (2016, 2016.11.20). Around a Camphoric Acid boat, is the surfactant adsorbed on to the interface or dissolved in the bulk?, Portland, Oregon, USA.
  8. Bandi, M. M., Nguyen, K. D. (2016, 2016.11.21). Stiffness modulation of Rayed fins by curvature, Portland, Oregon, USA.

4.4 Seminars

  1. Akella, V. S., Singh, D. K., Singh, R. K., Mandre, S., Bandi, M. M. (2016). Dynamics of Camphoric Acid Boat at the Air-Water Interface. TIFR Mumbai, India.
  2. Akella, V. S., Singh, D. K., Singh, R. K., Mandre, S., Bandi, M. M. (2016). Dynamics of Camphoric Acid Boat at the Air-Water Interface. IISc Bangalore, India.
  3. Akella, V. S., Singh, D. K., Singh, R. K., Mandre, S., Bandi, M. M. (2016). Dynamics of Camphoric Acid Boat at the Air-Water Interface. TIFR Hyderabad, India.
  4. Bandi, M. M. (2016). Spectrum of wind power fluctuation. Tata Institute of Fundamental Research, Mumbai, India.
  5. Bandi, M. M. (2016). The Spectrum of Wind Power Fluctuations. Physics of Complex Systems, Department of Physics, Phillips University, Marburg, Germany.
  6. Singh, D. K., Bandi, M. M. (2016). Use of 3D photoelastic model to extract three components of traction. EMU, JNCASR, Bangalore, India.
  7. Singh, D. K., Bandi, M. M. (2016). Use of 3D photoelastic model to extract three components of traction. Mechanical department, iisc, Bangalore, India.

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6.1 Seminars

  • Seminar Title: Compressing the Incompressible
  • Date: April 11, 2016
  • Venue: OIST campus Lab 2
  • Speaker: Dr. Ildoo Kim
  • Seminar Title: Curvature-guided motility of microalgae in geometric confinement
  • Date: September 9, 2016
  • Venue: OIST campus Lab 2
  • Speaker: Mr. Thomas Boeddeker
  • Seminar Title: Visualization and characterization of quantum fluid flows
  • Date: April 7, 2016
  • Venue: OIST campus Center Building
  • Speaker: Prof. Daniel Lathrop
  • Seminar Title: Liquid Sodium Models of the Earth's Core
  • Date: April 8, 2016
  • Venue: OIST campus Center Building
  • Speaker: Prof. Daniel Lathrop
  • Seminar Title: The Dynamical Slowing Down of Colloidal Clay Suspensions of Laponite: Similarities with Supercooled Liquids
  • Date: April 18, 2016
  • Venue: OIST campus Lab 1
  • Speaker: Prof. Ranjini Bandyopadhyay

7. Other

Nothing to report.