FY2014 Annual Report

Fluid Mechanics Unit

Associate Professor Pinaki Chakraborty


The Fluid Mechanics unit pursued research on turbulent flows, atmospheric flows, and granular flows, and continued to develop a joint fluid mechanics--continuum physics laboratory.

1. Staff

  • Prof. Pinaki Chakraborty, Associate Professor
  • Dr. Chien-chia Liu, Researcher
  • Dr. Rory Cerbus, Researcher
  • Mr. Christian Butcher, Technical Staff
  • Ms. Yoriko Yamamura, Graduate Student (Research Rotation)
  • Ms. Maki Kohata Thomas, Graduate Student (Research Rotation)
  • Mr. Yafei Mao, Graduate Student (Research Rotation)
  • Kaori Egashira, Research Administrator

2. Collaborations

  • Theme: Turbulent soap films
    • Type of collaboration: Scientific collabolation
    • Researchers:
      • Professor Hamid Kellay, University of Bordeaux, France
      • Professor Walter Goldburg, University of Pittsburgh, USA
  • Theme: Energetics of two-dimensional turbulence in soap films
    • Type of collaboration: Scientific collaboration
    • Researchers:
      • Professor Gregory Falkovich, Weizmann Institute of Science, Israel

  • Theme: Theory of spectral link in turbulent flows
    • Type of collaboration: Scientific collaboration
    • Researchers:
      • Professor Gustavo Gioia, OIST
  • Theme: Experiments on granular cratering
    • Type of collaboration: Scientific collaboration
    • Researchers:
      • Professor Gustavo Gioia, OIST
      • Professor Susan Kieffer, University of Illinois at Urbana-Champaign, USA

  • Theme: Experiments on turbulent pipe flows
    • Type of collaboration: Scientific collaboration
    • Researchers:
      • Professor Gustavo Gioia, OIST
      • Professor Jun Sakakibara, Meiji University, Japan
  • Theme: Development of Taylor-Couette experiment
    • Type of collaboration: Scientific collaboration
    • Researchers:
      • Dr. Yasuo Higashi, OIST
      • Professor Gustavo Gioia, OIST

3. Activities and Findings

3.1 Anisotropic cascades in turbulent soap films

Many large-scale atmospheric and oceanic flows are decaying two dimensional turbulent flows embedded in a non-uniform mean flow. Despite its importance for large-scale weather systems, the influence of non-uniform mean flows on decaying 2D turbulence remains unknown. In the absence of any mean flow it is well known that decaying 2D turbulent flows partake in the enstrophy cascade. In this cascade, as is typical of all classical turbulent cascades, the longitudinal and transverse velocity fluctuations correspond to the same cascade, signifying isotropy. Indeed isotropy is a key concept that informs the phenomenological theory of 2D turbulence. To study the influence of non-uniform mean flow on decaying 2D turbulence we have performed experiments on turbulent soap films. We find that the flow transitions from the usual isotropic enstrophy cascade to a series of unusual and, to our knowledge, never before observed or predicted, anisotropic cascades where the longitudinal and transverse spectra are mutually independent and partake in different cascades. We are working on the implications of our results for decaying geophysical turbulence.

Figure: Mean flow--turbulence interaction in soap-film flows. The mean flow in each panel is from top to bottom; the panels from left to right show the progressive development of anisotropic turbulence.

3.2 Spectral link in turbulent plane-Couette flows

There is a long standing mystery concerning friction drag in one of the simplest canonical wall-bounded flows: fully developed turbulent plane Couette flows.  Manifestly defying predictions from dimensional analysis, experiments have consistently shown that the frictional drag, f, is not a unique function of the Reynolds number, Re. In fact, the f vs. Re data fall on two disparate curves. The origin of these two curves dates back to the 1950s when Reichardt and Robertson independently performed their classical experiments. Subsequent works have found f vs. Re data to be in accord with the Reichardt curve or with the Robertson curve. While the disparity in the f vs. Re data are well known, we have identified an hitherto undetected attendant disparities in the mean velocity profile, in particular regarding the presence or absence of an overshooting wake. Based on the theory of spectral link we show that these disparities are but manifestations of the same underlying physics: the affect of finite-domain on the turbulent energy spectrum.

3.3 Physical origin of the classical laws of wall-bounded turbulent flows

Since the pioneering work of Prandtl and von Karman in the 1930s, the classic laws dictating the scaling of mean-velocity profiles (MVPs) in wall-bounded flows have been predicated solely on dimensional analysis and similarity assumptions that concern the MVPs in the limit of zero viscosity and infinite domain. In other words, the classic laws that govern the scaling of MVPs are based on assumptions that pertain to nothing else but the MVPs themselves. Building on two of our previous findings in the theory of wall turbulence---the spectral link and the spectral analogs---we mathematically derive these classic laws based on a cardinal attribute of turbulent flows that has no obvious ties with the MVPs: the turbulent energy spectrum. Based on the empirical property that viscosity and finite turbulent domains have a depressive effect on the turbulent energy spectrum, we evince the physical origin of the classic laws. Our work suggests that further physical insight into the MVPs and other phenomena of wall turbulence will be gained by exploiting the large corpus of available knowledge on the turbulent energy spectrum and the physics of turbulent fluctuations.

3.4 Rainpower and hurricane intensity

In previous work we have identified the effect of rainpower (power lost to friction in falling rain) on the intensity of a hurricane. By analyzing satellite data and by using the framework of a simple analytical model of hurricane energetics, we demonstrated that, contrary to the prevalent notion that rain helps drive hurricane winds, the general effect of rainpower is to lessen the steady-state hurricane intensity by 20% on average. Proceeding beyond the simple analytical model, we now incorporate rainpower in a state-of-the-art, time-dependent computational model, Cloud Model 1 (CM1). Our preliminary results suggest that rainpower triggers an inverse energy flux that effects in lessening of the steady-state hurricane intensity by 15% on average. Beyond the effect on steady-state intensity, we find that during the initial "rapid intensification" stage the hurricane intensities are increased by 50% on average.

3.5 Granular cratering

We have continued experiments on granular cratering. Using high-speed imaging we are studying the development of distinctive morphology in the crater ejecta. To complement our experimental observations, we are conducting three-dimensional simulations of granular cratering using LIGGGHTS (LAMMPS Improved for General Granular and Granular Heat Transfer Simulations).

3.6 Experiments on turbulent pipe flows

We have continued experiments on turbulent pipe flows. In laminar, transitional, and fully-developed turbulence regimes,
we are able to obtain accurate measurements of pressure drop (via pressure transducers) and of temporally and spatially resolved velocity field (via Stereoscopic Particle Image Velocimetry, S-PIV). Our experimental data is in excellent accord with benchmark data from state-of-the-art Direct Numerical Simulations.

3.7 Experiments on turbulent Taylor-Couette flows

We have continued development of a large Taylor-Couette experiment. With air as the working fluid we have measured the turbulent energy spectrum (via hot-wire anemometry). Our preliminary results suggest that multiple flow states, as discerned using the turbulent energy spectrum, can be triggered by movement of an intrusive probe, all the while keeping the phase-space parameters (such as cylinder angular velocity) constant. We have began work on modifying the setup to use water as the working fluid.

4. Publications

4.1 Journals

  1. C. Zuniga Zamalloa, H. C-H Ng, P. Chakraborty, and G. Gioia. 2014. Spectral analogues of the law of the wall, the defect law and the log law. Journal of Fluid Mechanics, vol. 757, pp. 498-513
  2. T. Sabuwala, G. Gioia, and P. Chakraborty. 2015. Effect of rainpower on hurricane intensity. Geophysical Research Letters, vol. 42 (8), pp. 3024-3029, doi:10.1002/2015GL063785

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

  1. Chakraborty, P.  Turbulent soap-film flow, Joint Seminar between OIST and JST mathematics program on vortex-boundary interactions and wall-bounded turbulent flows, Okinawa, Japan, May 26 (2014).
  2. Cerbus, R., Samanta, D., Ingremeau, F., Tran, T., Goldburg, W., Chakraborty, P., Kellay, H.  The scaling of near-wall flows in quasi-two dimensional turbulent channels, Frontiers of turbulence research, Kyoto, Japan, July 25 (2014).
  3. Chakraborty, P., Zamalloa, C., Ng, H., Gioia, G.  Spectral analogs of the law of the wall, the defect law, and the log law, Frontiers of turbulence research, Kyoto, Japan, July 25 (2014).
  4. Liu, C., Gioia, G., Chakraborty, P.  Frictional drag and mean-velocity profile in non-uniform, quasi-two-dimentional turbulent channels, Frontiers of turbulence research, Kyoto, Japan, July 25 (2014).
  5. Sabuwala, T., Gioia, G., Chakraborty, P.  Hurricane intensity modulation by rain-induced frictional dissipation, Asia Oceania Geosciences Society 11th Annual Meeting, Sapporo, Japan, July 28 (2014).
  6. Chakraborty, P.  The spectral link in turbulent frictional drag of uniform and non-uniform flows, The 52th Meeting of the Society for Natural Philosophy, Rio De Janeiro, Brazil, October 24 (2014).
  7. Chakraborty, P.  Overview of spectral link in turbulent friction, Join-seminar on physics of typhoons: theory and simulations, Okinawa, Japan, February 6 (2015).
  8. Cerbus, R., Goldburg, W.  Information theory used to study the turbulent cascade, APS March Meeting 2015, San Antonio, USA, March 4 (2015).
  9. Liu, C., Cerbus, R., Gioia, G., Chakraborty, P.  Mutually independent cascades in anisotropic soap-film turbulence, APS March Meeting 2015, San Antonio, USA, March 4 (2015).
  10. Zhang, D., Gioia, G., Chakraborty, P.  The spectral link in mean-velocity profile of turbulent plane-Couette flows, APS March Meeting 2015, San Antonio, USA, March 4 (2015).

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6-1. Joint seminar

(1) Joint seminar between OIST and JST mathematics program on vortex-boundary interactions and wall-bounded turbulent flows
  • Date: May 26, 2014
  • Venue: OIST
  • Organizers: Prof. Pinaki Chakraborty (OIST), Prof. Takashi Sakajo (Kyoto University)
  • Speakers:
    • Prof. Akio Nakahara (Nihon University)
    • Prof. Pinaki Chakraborty (OIST)
    • Prof. Gustavo Gioia (OIST)
    • Prof. Takashi Sakajo (Kyoto University)
    • Prof. Zin Arai (Hokkaido University)
    • Prof. Takashi Ishihara (Nagoya University)
    • Prof. Tomoo Yokoyama (Kyoto University of Education)
    • Dr. Rhodri Nelson (Kyoto University)
(2) Joint seminar on physics of typhoons; theory and simulations
  • Date: February 6, 2015
  • Venue: OIST
  • Speakers:
    • Dr. Akiyoshi Wada (Meteorological Research Institute, Japan Meteorological Agency)
    • Prof. Kosuke Ito (University of the Ryukyus)
    • Prof. Pinaki Chakraborty (OIST)
    • Dr. Tapan Sabuwala (OIST)

6.2 Seminar

(1) Title: Dense-gas shock-refraction properties
  • Date: April 18, 2014
  • Venue: OIST
  • Speaker: Prof. Emile Touber (Imperial College London, England)
(2) Title: The Spectral Link in Turbulent Frictional Drag and Turbulent Mean Velocity Profile
  • Date: August 5, 2014
  • Venue: JAXA (Kanagawa, Japan)
  • Speaker: Prof. Pinaki Chakraborty (OIST)
(3) Title: Coral Reef Ecosystems on a Warming Planet: Lessons from Yellowstone Hot Springs
  • Date: November 5, 2014
  • Venue: OIST
  • Speaker: Prof. Bruce W. Fouke (University of Illinois Urbana-Champaign)
  • Funding: American Association of Petroleum Geologists Distinguished Lectureship
(4) Title:  A Soapy approach to understanding turbulent friction
  • Date: December 12, 2014
  • Venue: OIST
  • Speaker: Prof. Pinaki Chakraborty (OIST)
(5) Title: Droplet impact on solid surfaces: the effect of air and vapor
  • Date: January 7, 2015
  • Venue: OIST
  • Speaker: Prof. Tuan Tran (Nanyang Technological University, Singapore)
(6) Title:  Pair dispersion in turbulence: The permanent and the irreversible
  • Date: February 23, 2015
  • Venue: OIST
  • Speaker: Ms. Anna Frishman (Weizmann Institute of Science, Israel)
(7) Title:  What drives weather changes?
  • Date: February 23, 2015
  • Venue: OIST
  • Speaker: Prof. Gregory Falkovich (Weizmann Institute of Science, Israel)

6.3 Mini-Course

  • Title:  Fluid mechanics in two hours
  • Date: February 24 & Ferbruary 26, 2015
  • Venue: OIST
  • Speaker: Prof. Gregory Falkovich (Weizmann Institute of Science, Israel)


7. Other

Nothing to report.