FY2012 Annual Report

Fluid Mechanics Unit

Associate Professor Pinaki Chakraborty

Abstract

The Fluid Mechanics unit pursued research on turbulent flows, tropical cyclones, and volcanic eruptions, and started a joint fluid mechanics--continuum physics laboratory at OIST.

1. Staff

Dr. Pinaki Chakraborty, Associate Professor
Dr. Chien-Chia Liu, Researcher
Dr. Carlo Cesar Zuniga Zamalloa, Researcher
Ms. Kaori Egashira, Research Administrator

2. Collaborations

Theme: Turbulent flows
- Type of collaboration: Scientific collaboration
- Researchers:
  - Professor Gustavo Gioia, OIST
  - Professor Walter Goldburgh, University of Pittsburgh, USA
  - Professor Hamid Kellay, University of Bordeaux, France
  - Professor Nigel Goldenfeld, University of Illinois, USA
Theme: Tropical cyclones
- Type of collaboration: Scientific collaboration
- Researchers:
  - Professor Gustavo Gioia, OIST
Theme: Large-scale volcanic eruptions
- Type of collaboration: Scientific collaboration
- Researchers:
  - Professor Craig Lundstrom, University of Illinois, USA
  - Professor Susan Kieffer, University of Illinois, USA

3. Activities and Findings

- We have designed a soap-film channel where the spectral exponent changes between the two theoretically possible exponents (one associated with inverse energy cascade and the other with enstrophy cascade) across the width of the flow. By measuring the frictional drag on the smooth channel walls as a function of the Reynolds number of the flow, we demonstrated that a local version of the spectral link determines the scaling of the frictional drag. Our results broaden the scope of the theory of spectral link for turbulent friction.

- Using dimensional analysis and similarity arguments, we have derived new scaling relations for the energy spectra in turbulent flows over smooth walls. These relations are spectral analogues of the well-known scaling relations for the mean-velocity profile: the law of the wall, the log law, and the defect law. We have tested the new relations using spectral data from Direct Numerical Simulations and experiments in pipe flows and channel flows.

- Using a combination of theory and remote sensing, we performed the first computations of the entropic contribution of rain-induced dissipation in the eyewall of mature hurricanes. Further, we showed that this contribution leads to substantial decrease in the maximum potential intensity of the hurricane.

- We are working on a thermodynamic model for the dissolution of silicate mush and the subsequent triggering of large-scale volcanic eruptions.

- In collaboration with the Continuum Physics unit, we started a joint fluid mechanics--continuum physics laboratory at OIST. To date the experimental facilities in laboratory include a vertical soap-film channel and turbulent pipe flow setups, and Stereo-PIV and mini-LDV flow-interrogation systems.

4. Publications

4.1 Journals

Kellay, H., Tran, T., Goldburg, W., Goldenfeld, N., Gioia, G. & Chakraborty, P. Testing a missing spectral link in turbulence. Physical Review Letters 109, (254502-1) ~ (254502-5), doi:10.1103/PhysRevLett.109.254502 (2012).

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

Cerbus, R., Goldburg, W., Chakraborty, P., Flynn, N. & Liu, C.-C. Energy spectra in polymer-doped turbulent soap films, in Annual Meeting of American Physical Society-Division of Fluid Dynamics (APS-DFD), San Diego, California, USA (2012).
Chakraborty, P., Kellay, H., Tran, T., Goldburg, W., Goldenfeld, N. & Gioia, G. Experimental test of a missing spectral link in turbulence, in Annual Meeting of American Physical Society-Division of Fluid Dynamics (APS-DFD), San Diego, California, USA (2012).
Gioia, G., Zamalloa, C. Z. & Chakraborty, P. Spectral analogue of the law of the wall, in Annual Meeting of American Physical Society-Division of Fluid Dynamics (APS-DFD), San Diego, California, USA (2012).
Liu, C.-C., Cerbus, R., Goldburg, W., Gioia, G. & Chakraborty, P. The spectral link for frictional drag in non-uniform turbulent soap-film flows, in Annual Meeting of American Physical Society-Division of Fluid Dynamics (APS-DFD), San Diego, California, USA (2012).
Sabuwala, T., Gioia, G. & Chakraborty, P. Rain-induced dissipation in hurricanes, in Annual Meeting of American Physical Society-Division of Fluid Dynamics (APS-DFD), San Diego, California, USA (2012).
Sabuwala, T., Gioia, G. & Chakraborty, P. Rain-induced dissipation in hurricanes, in 25th Conference on Climate Variability and Change, 93rd AMS Annual Meeting, Austin, Texas, USA (2013).
Zamalloa, C. Z., Gioia, G. & Chakraborty, P. Experimental test of the spectral analogue of the law of the wall in rough-pipe flows, in Annual Meeting of American Physical Society-Division of Fluid Dynamics (APS-DFD), San Diego, California, USA (2012).

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6.1 Seminar

Title: Turbulent Rayleigh--Taylor Instabilities: a tale of two volcanoes
Date: November 16, 2012
Venue: Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California at San Diego, San Diego, California, USA
Speaker: Prof. Pinaki Chakraborty (OIST)

6.2 Seminar

Title: The spectral link in turbulence
Date: January 11, 2013
Venue: Fluids Engineering Laboratory, Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan
Speakers: Prof. Pinaki Chakraborty (OIST)

6.3 Seminar

Title: Enceladus, the Moon of Saturn: Oasis or Ice Ball?
Date: February 22, 2013
Venue: OIST Campus Lab1
Speaker: Prof. Susan Kieffer (The Walgeen-chair professor of Geology, Physics, and Center for Advanced Studies at the University of Illinois at Urbana-Champaign, USA)