Strategic Young Researcher Overseas Visits Programfor Accelerating Brain Circulation 2011
“Development of Young Researchers
Based on International Joint Research
on Green Energy Systems”
Progress Report

1. Name: Tomohiko Yamaguchi
2. Title: Associate Professor
3. Host Institution: University of Nottingham (England)
4. Host Researcher: Professor Yuying Yan
5. Duration: 18-August-2012 – 05-October-2013
6. Research Topic:
Study for the heat and mass transfer on biomimetic functional surfac
es and phase changes in order to develop next-generation technologies on the green energy
7. Overview of the Results of the Collaborative Research:
Development of athermal Lattice Boltzmann method for two-phase flow with large
density difference in complex boundary structure
The heat pipe is one of the interesting thermal devices nowadays. If we want to improve
the performance of the heat pipe, the wick structure and knowledge of vapour-liquid
two-phase flow in the wick are important, because these significantly affect theperformance of the heat pipe. Since the wick structure and the two-phase flow in the wickare very complex, we want to simulate two-phase flow in the wick numerically.

In order to simulate two-phase flow in the sintered wick of heat pipes, we compute themass transfer of two-phase flow having large density difference in the complex boundary
by a lattice Boltzmann method (LBM) proposed by Inamuro et al in 2004 and Yan et al in2010. We introduced following two points to this simulation method. One of our aims is tosimulate the two-phase flow in a sintered wick. So we want to adapt the numerical method
to the complex boundary. We added an extra layer to the boundary and calculated thevalues on these lattices by extrapolation method. Moreover, the interpolation function of
the viscosity coefficient was modified to satisfy the continuity of the viscosity flux acrossthe phase interface. Since the values of viscosity are quite different between the liquid andthe gas phase, the viscosity in the transition region affects the results. Figures 1 and 2 show
the aggregation behaviour of large density phase from random density distribution, and thebehaviour of bubbles between spheres arranged in a face centred cubic lattice, respectively.
We have succeeded in simulating two-phase flow having large density difference by LBM.
We are going to implement a thermal model and control of the wettability as our future
work.

Fig. 1 Result of simulation: aggregation behaviour oflarge density phase from random density
distribution

Fig. 2 Result of simulation: behaviour of
bubbles between spheres arranged
in face centred cubic lattice

MRI measurement of water transport in plant stem
Prof Yan’s group and I are trying to measure the water transport in the plant stem bymeans of MRI in order to improve the water transport and structure of the wick in the heatpipe. The tall trees can deliver the water up to more than tens of metre height. We intend toget the hints to improve the performance of thermal devices from nature. Figure 3 shows asample small plant, named ‘Salix Flamingo’, in which we had measured water distribution
as a pilot study. Figure 4 shows a result of measurement visualised by MATLAB. We cansee that the water is circumferentially deflected in the stem.

Fig. 3 Picture of the 3-tesla MRI and a plantFig.4 Water concentration profile in a plantstem

8. Deployment Plans for Future Collaborative Research:
Prof Yan and I have an agreement to continue our collaboration on the research of thelattice Boltzmann method for two-phase flow with the large density difference. We intend
to extend our simulation program of LBM to the thermal model.
Since we want to continue the MRI measurement of the water delivery in plant’s stemin order to improve the performance of heat pipe, we are going to advance our research ateach institute. Prof Yan can use MRI facilities at MR center in the University of
Nottingham and I will be able to use MRI facilities at Nagasaki University Hospital.
Moreover, we are applying for some research funds.

9. List of Collaborative Research Progress:Publication(s)1) Yamaguchi, T., Wan, Q., Yan, Y.Y. and Hong, J., Numerical simulation of liquid-gas
two-phase flow with large density difference in multi-layered sintered wick by the lattice
Boltzmann method, Proceedings of 15th International Heat Transfer Conference, Kyoto,
Japan, 2014.8, (under review)2) Yamaguchi, T., Wan, Q. and Yan, Y.Y., Numerical analysis of two-phase flow in sinteredcopper wick by lattice Boltzmann method, Proceedings of the ASME 2013 11thInternational Conference on Nanochannels, Microchannels, and Minichannels (CD-ROM),
Sapporo, Japan, 2013.6, ICNMM2013-73205

Conference Presentations

1) Yamaguchi, T., Wan, Q., Yan, Y.Y. and Hong, J., Numerical simulation of liquid-gas
two-phase flow with large density difference in multi-layered sintered wick by the lattice
Boltzmann method, 15th International Heat Transfer Conference, Kyoto, Japan, 2014.8,(under review)2) Yamaguchi, T., Lattice Boltzmann simulation of liquid-gas two-phase flow with large
density difference in complex boundary, Keynote speech in the International Heat Transfer
Symposium 2014 (IHTS2014), 2014.5, Beijing, China, IHTS14K0043) Yamaguchi, T. and Yan, Y.Y., Numerical simulation of liquid-gas two-phase flow insintered wick with face-centred structure by the athermal Lattice Boltzmann Method, 9thUK–Japan Seminar on Multi-Phase Flows 2013, London, UK, 2013.94) Yamaguchi, T., Wan, Q. and Yan, Y.Y., Numerical simulation of liquid-gas two phase-flow
in sintered wick with face-centred structure by the athermal Lattice Boltzmann Method,
13th UK Heat Transfer Confernece 2013, London, UK, 2013.9, UKHTC2013-185
5) Yamaguchi, T., Wan, Q. and Yan, Y.Y., Numerical analysis of two-phase flow in sinteredcopper wick by lattice Boltzmann method, The ASME 2013 11th International Conferenceon

Nanochannels,Microchannels,andMinichannels,

Sapporo,Japan,2013.6,

ICNMM2013-73205
6) Yamaguchi, T., Numerical Analysis of Bubbles Flow in 3D Sintered Wick by Lattice
Boltzmann Method, Invited presentation at International workshop on “Numerical heat andmass transfer from a view point of multiscale analysis”, Nottingham, UK, 2013.5