FY2015 Annual Report

Continuum Physics Unit
Professor Gustavo Gioia

Abstract

The Continuum Physics Unit pursued theoretical and experimental research on turbulent flows and granular materials, and continued to develop a joint fluid mechanics--continuum physics laboratory at OIST.

 

1. Staff

  • Dr. Tapan Sabuwala, Research Specialist
  • Dr. Tinihau Meuel, Researcher
  • Mr. Dongrong Zhang, Graduate Student
  • Ms. Kaori Egashira, Research Unit Administrator

 

2. Collaborations

2.1 The spectral link in turbulent flows

  • Type of collaboration: Scientific collaboration
  • Researchers:
    • Professor Pinaki Chakraborty, OIST

2.2 Granular cratering

  • Type of collaboration: Scientific collaboration
  • Researchers:
    • Professor Pinaki Chakraborty, OIST
    • Professor Susan Kieffer, University of Illinois, USA

2.3 Experiments on turbulent pipe flows

  • Type of collaboration: Scientific collaboration
  • Researchers:
    • Professor Pinaki Chakraborty, OIST
    • Professor Jun Sakakibara, Meiji University, Japan

2.4 Experiments on Taylor-Couette flows

  • Type of collaboration: Scientific collaboration
  • Researchers:
    • Dr. Yasuo Higashi, OIST
    • Professor Pinaki Chakraborty, OIST

 

 

3. Activities and Findings

-We have carried out theoretical and experimental research on transitional pipe flows (generally defined as flows of Reynolds number on the order of 1000). It is accepted that for Re > 3000 transitional flows are essentially inhomogeneous and consist of laminar patches and turbulent patches that alternate with one another along the axis of a pipe. In previous experimental work it was shown that the turbulent patches, known as slugs, may vary in length between a few pipe diameters and the entire length of a pipe, but little is known, experimentally, as to the type of turbulence (internal structure, statistical signatures) that prevails in the slugs. By carrying out stereo particle-image-velocimetry measurements in the fluid mechanics-continuum physics pipe-flow facility at OIST, we have been able to show that it is possible to determine experimentally the mean-velocity profiles, frictional drag-Re curves and other average properties of slugs (as opposed to the average properties of the transitional flow as a whole). It turns out that the mean-velocity profiles and frictional drag-Re curves of slugs are indistinguishable from those of fully-developed turbulent pipe flow. Further, it turns out that "slug turbulence" displays statistical signatures consistent with the phenomenological theory of turbulence, with the implication that slugs may be amenable to theoretical treatment via the spectral link (which has been the leitmotiv of our research on turbulence). We are currently working out this theoretical implication of our experimental results with the objective of formulating a predictive, falsifiable spectral theory of slugs (and, eventually, a spectral theory of transitional pipe flow). The experiments themselves continue at a steady pace.

- Theoretical turbulent research carried out in FY 2015 has also included continuing work on a certain anomaly in the mean-velocity profiles of pipe flow, which anomaly we discovered in FY 2014, and which we have now been able to explain via the spectral link. It turns out that the anomaly in the mean-velocity profiles is but a manifestation of a well-known but poorly understood phenomenon associated with the spectrum of turbulent energy. Thus the mean-velocity profiles are inextricably linked to, and can indeed be interpreted as macroscopic manifestations of, the spectrum of turbulent energy--not just in general terms, concerning conspicuous and salient features, but also in detail, down to the level of a minute anomaly that has hardly been noticed in the vast literature on turbulent pipe flows.

- In addition, we have carried out further theoretical work on the scaling of the profiles of turbulent intensity in pipe and Taylor-Couette flows (this is a project that started in FY 2014), with results that are encouraging but remain incomplete.

- We have continued development of the OIST Taylor-Couette experimental facility. (The Taylor-Couette experiment features two concentric cylinders that rotate relative to one another). Using water as the working fluid, we have carried out preliminary measurements of the torque on the inner cylinder and the azimuthal velocity profile in the gap between the cylinders. We have also started work using rough cylinders.

- We have continued working on impact cratering in granular beds. New research on this topic has included an extensive series of large-scale three-dimensional computational simulations of impact cratering, using the granular-dynamics code LAMMPS. The results have been in excellent accord with the experimental results that we obtained during FY 2014 in the joint fluid mechanics-continuum physics granular-flow laboratory at OIST. We are currently working on the geological implication that our results, which appear to shed new light on the type of crater, common on the Moon and on Mars, in which the debris blanket include filamentary rays that have long defied theoretical explanation.

 

 

4. Publications

4.1 Journals

Nothing to report

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

  1. Cerbus, R., Liu, C., Gioia, G., Chakraborty, P. Cascade transition and anisotropy in decaying 2D turbulence, RIMS Kyoto: Fluid phenomena mediated by turbulence, Kyoto, Japan, July 24 (2015).
  2. Sabuwala, T. Gioia, G., Chakraborty, P. Effect of rainpower on hurricane intensity, 8th European Conference on Severe Storms- ECSS2015, Vienna, Austria, Sep.15 (2015).
  3. Cerbus, R.,  Liu, C., Chakraborty, P., Gioia, G. Evolution of cascades in 2D turbulence, JPS 2015 Autumn Meeting, Osaka, Japan, Sep.18 (2015).
  4. Liu, C., Cerbus, R., Gioia, G., Chakraborty, P. Mean flow and anisotropic cascades in decaying 2D turbulence, 68th Annual Meeting of the APS Division of Fluid Dynamics, Boston, USA, Nov.22 (2015).
  5. Cerbus, R., Liu, C., Sakakibara, J., Gioia, G., Chakraborty, P. Fully developed turbulence in slugs of pipe flows, 68th Annual Meeting of the APS Division of Fluid Dynamics, Boston, USA, Nov.23 (2015).
  6. Shinbrot, T., Chakraborty, P., Sabuwala, T. Itokawa is not Brazil: granular segregation on asteroids, 68th Annual Meeting of the APS Division of Fluid Dynamics, Boston, USA, Nov.23 (2015).
  7. Zhang, D., Gioia, G., Chakraborty, P. Non-unique frictional drag in turbulent plane Couette flows, 68th Annual Meeting of the APS Division of Fluid Dynamics, Boston, USA, Nov.24 (2015).
  8. Gioia, G. Teoría espectral de la fricción turbulenta en 3 y 2 dimensiones, University of Buenos Aires, Buenos Aires, Argentina, Mar.3 (2016).
  9. Gioia, G. Teoría espectral de la fricción turbulenta en 3 y 2 dimensiones, The Argentine Institute of Mathematics, Buenos Aires, Argentina, Mar.4 (2016).
  10. Shinbrot, T., Sabuwala, T., Siu, T., Lazo, M., Chakraborty, P. Itokawa: a case for ballistic segregation, APS March Meeting 2016, Baltimore, USA, Mar.15 (2016).
  11. Cerbus, R., Liu, C., Chakraborty, P., Sakakibara, J., Gioia, G. Fully developed turbulence in slugs from pipe flow, JPS Annual Spring Meeting. Miyagi, Japan, Mar.22 (2016)

 

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

 

6. Meetings and Events

6.1 Buckling of macroscopic metal-organic-framework nanofilms

  • Date: June 1, 2015
  • Venue: OIST Campus, Lab1
  • Speaker: Prof. Sahraoui Chaieb
     (King Abdullah University of Science and Technology, Saudi Arabia)

6.2 Lagrangian statistics and particle dispersion in two-dimensional turbulence

  • Date: February 16, 2016
  • Venue: OIST Campus, Lab1
  • Speaker: Prof. Michael Shats (The Australian National University)

6.3 Lattices, disorder and quasi-particles in Faraday waves: understanding fluid particle motion in surface waves

  • Date: February 18, 2016
  • Venue: OIST Campus, Lab1
  • Speaker: Prof. Michael Shats (The Australian National University)

6.4 Quantifying Roughness Effects on Frictional Drag

  • Date: March 17, 2016
  • Venue: OIST Campus, Center building
  • Speaker: Prof. Michael Schultz (United States Naval Academy)

 

6.5 What you see is what you understand: explaining two-phase flows at different scales with computational and theoretical approaches

  • Date: March 25, 2016
  • Venue: OIST Campus, Lab1
  • Speaker: Prof. Fabian Bomberdelli (University of California, Davis)

 

 

7. Other

Nothing to report.