FY2016 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

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

2.5 Granular segregation on asteroid Itokawa

  • Type of collaboration: Scientific collaboration
  • Researchers:
    • Professor Troy Shinbrot, Rutgers University
    • Professor Pinaki Chakraborty, OIST

3. Activities and Findings

- In the early twentieth century, Ludwig Prandtl formulated the classic laws of the mean-velocity profiles (MVPs) of wall-bounded turbulent flows: the ‘law of the wall,’ the ‘defect law’ and the ‘log law.’ In Prandtl's formulation, the classic laws may be described as a suitable set of assumptions regarding the asymptotic behavior of the MVPs in the limits of vanishing viscosity and infinite turbulent domain. In this project we seek to link the classic laws to the turbulent eddies (or fluctuations) of a flow, which are the carriers of the flow’s turbulent kinetic energy. Our preliminary results suggest that the classic laws are inextricably linked with the manner in which that energy is apportioned amongst the eddies of the flow, i.e., to the spectrum of turbulent energy or ``turbulent spectrum."

- A classic indicator of the type of flow in a pipe is the relation between the dimensionless pressure drop per unit length of pipe (known as the fluid friction) and the Reynolds number. When the flow is laminar, f (the fluid friction) scales as Re^{-1}, where Re is the Reynolds number. This scaling of f with Re is known as the Hagen--Poiseuille law. When the flow is turbulent, f scales as Re^{-1/4}, which is known as the Blasius law. In between the laminar and turbulent states, the flow is transitional, and the attendant relation between f and Re is not known. Using pipe-flow experiments and direct numerical simulations, we are studing the scaling relation bewteen f and Re for the transitional state.

- 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). We have implemented temperature control of the working fluid. In addition, we have procured rough-walled inner cylinders which allow us to explore rough-walled turbulent Taylor-Couette flow, a type of flow for which there is a notable scarcity of experimental data. As compared to flow over smooth walls, flow over rough walls necessitates much higher driving torques, which cause significant temperature increases in the working fluid. If the temprature is not controlled, the attendant changes in viscosity cannot be factored in the interpretation of the experimental results. Thus temperature control is a crucial component of rough-walled Taylor-Couette experiments.

- We have continued working on impact cratering in granular beds with an undulating surface. We aim has been to elucidate the mechanism underlying the formation of debris blankets that include filamentary rays, a type of debris blanket that has long defied theoretical explanation. Our preliminary results suggest that filamentary rays are caused by surface topography, a factor that has hitherto remained unexplored in empirical studies of impact cratering in granular beds.

- Photographs from the Hayabusa spacecraft mission revealed a strong lateral segregation between regions of large boulders and regions of small pebbles on the rubble-pile asteroid Itokawa. We argue that the current understanding of what causes this segregation is inconsistent with observations, and propose an alternative, simple model that encompasses the entire processes of asteroid formation. Using experiments and discrete-element simulations, we show how the model proposed leads to the observed size segregation on Itokawa. This project was carried out by Dr. Tapan Sabuwala as a collaborative research.
 

4. Publications

4.1 Journals

  1. Shinbrot, T., Sabuwala, T., Siu, M., Chakraborty, P. 2017. Size Sorting on the Rubble-Pile Asteroid Itokawa. Physical Review Letters, vol. 118, PP.111101, DOI10.1103/PhysRevLett.118.111101.

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

  1. Cerbus, R., Liu, C., Sakakibara, J., Gioia, G., Chakraborty, P., The mean velocity profile in turbulent slugs, RIMS International Project Research 2016, Fluid Dynamics of Near-Wall Turbulence, Kyoto, Japan, June 21 (2016).
  2. Zhang, D., Gioia, G., Chakraborty, P., Macroscopic non-universality in turbulent plane-Couette flows, RIMS International Project Research 2016, Fluid Dynamics of Near-Wall Turbulence, Kyoto, Japan, June 21 (2016).
  3. Chakraborty, P., Cerbus, R., Liu, C., Gioia, G., Energy cascade in Reynolds' flashes, Emerging topics in Soft Matter, OIST, Okinawa, Japan, August 17 (2016).
  4. Sabuwala, T., Chakraborty, P., Gioia, G., Effect of rain-induced turbulent dissipation on hurricane intensity, Emerging topics in Soft Matter, OIST, Okinawa, Japan, August 17 (2016).
  5. Zhang, D., Gioia, G., Chakraborty, P., Spectral link for the mean velocity profile in the atmospheric boundary layer, VIIIth International Symposium on Stratified Flows, San Diego, California, USA, August 31 (2016).
  6. Cerbus, R., Liu, C., Li, L., Butcher, C., Gioia, G., Chakraborty, P., Transition is Turbulence, Japan Physical Society Annual Fall Meeting, Kanazawa University, Ishikawa, Japan, September 13 (2016).
  7. Zhang, D., Gioia, G., Chakraborty, P., Spectral link for the mean velocity profile in the atmospheric boundary layer, 69th Annual Meeting of the APS Division of Fluid Dynamics, Portland, Oregon, USA, November 21 (2016).
  8. Cerbus, R., Liu, C., Gioia, G., Chakraborty, P., Turbulence in Reynolds' flashes, 69th Annual Meeting of the APS Division of Fluid Dynamics, Portland, Oregon, USA, November 22 (2016).
  9. Cerbus, R., Liu, C., Sakakibara, J., Gioia, G., Chakraborty, P., Energy cascade in transitional pipe flows, Dynamics Days Asia-Pacific (DDAP), Hongkong, December 17 (2016).
  10. Gioia, G., Cerbus, R., Liu, C., Chakraborty, P., Kolmogorovian turbulence in transitional pipe flows, Nanyang Technological University, Singapore, February 21 (2017).
  11. Gioia, G., Cerbus, R., Liu, C., Chakraborty, P., Kolmogorovian turbulence in transitional pipe flows, Imperial College London, England, February 27 (2017).
  12. Gioia, G., Chakraborty, P., A spectral theory of the mean-velocity profile in turbulent pipe flows, Imperial College London, England, February 27 (2017).
  13. Gioia, G., Cerbus, R., Liu, C., Chakraborty, P., Kolmogorovian turbulence in transitional pipe flows, KTH Royal Institutte of Technology, Sweden, March 7 (2017).
  14. Gioia, G., Cerbus, R., Liu, C., Chakraborty, P., Kolmogorovian turbulence in transitional pipe flows, University of Bordeaux, France, March 23 (2017).

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6.1 Some aspects of flows in soap films

Date: February 10th, 2017

Venue: OIST Campus, Lab1

Speaker: Prof. Guillermo ARTANA(UNIVERSITY OF BUENOS AIRES- CONICET- ARGENTINA)

 

6.2 Analyzing the Aeroelastic Dynamics of Wind Turbine Rotors in Rapid Pitch-Control Actions

Date: March 27th, 2017

Venue: OIST Campus, Lab1

Speaker: Prof. Fernando Ponta (Michigan Technological University)

7. Other

Nothing to report.