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 surfaces andphase changes in order to develop next-generation technologies on thegreen energy
7. Overview of the Results of the Collaborative Research:
Development of athermal Lattice Boltzmann method for two-phase flow withlarge density difference in complex boundary structure
The heat pipe is one of the interesting thermal devices nowadays. 	 If we want toimprove the performance of the heat pipe, the wick structure and knowledge ofvapour-liquid two-phase flow in the wick are important, because these significantly
affect the performance of the heat pipe. Since the wick structure and the two-phaseflow in the wick are 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 the mass transfer of two-phase flow having large density difference in thecomplex boundary by a lattice Boltzmann method (LBM) proposed by Inamuro et
al in 2004 and Yan et al in 2010. We introduced following two points to thissimulation method. One of our aims is to simulate the two-phase flow in a sinteredwick. So we want to adapt the numerical method to the complex boundary. We
added an extra layer to the boundary and calculated the values on these lattices byextrapolation method. Moreover, the interpolation function of the viscosity
coefficient was modified to satisfy the continuity of the viscosity flux across thephase interface. Since the values of viscosity are quite different between the liquid
and the gas phase, the viscosity in the transition region affects the results. Figures 1and 2 show the aggregation behaviour of large density phase from random density
distribution, and the behaviour of bubbles between spheres arranged in a facecentred cubic lattice, respectively. We have succeeded in simulating two-phaseflow 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 plantstem by means of MRI in order to improve the water transport and structure of thewick in the heat pipe. The tall trees can deliver the water up to more than tens ofmetre height. We intend to get the hints to improve the performance of thermal
devices from nature. Figure 3 shows a sample small plant, named ‘Salix Flamingo’,in which we had measured water distribution as a pilot study. Figure 4 shows aresult of measurement visualised by MATLAB. We can see that the water iscircumferentially 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 researchof the lattice Boltzmann method for two-phase flow with the large density
difference. We intend to extend our simulation program of LBM to the thermalmodel.
Since we want to continue the MRI measurement of the water delivery in plant’s
stem in order to improve the performance of heat pipe, we are going to advance ourresearch at each institute. Prof Yan can use MRI facilities at MR center in theUniversity 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 ofliquid-gas two-phase flow with large density difference in multi-layered sinteredwick 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 insintered copper wick by lattice Boltzmann method, Proceedings of the ASME 2013
11th International 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 ofliquid-gas two-phase flow with large density difference in multi-layered sinteredwick 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 withlarge density difference in complex boundary, Keynote speech in the InternationalHeat Transfer Symposium 2014 (IHTS2014), 2014.5, Beijing, China, IHTS14K0043) Yamaguchi, T. and Yan, Y.Y., Numerical simulation of liquid-gas two-phase flowin sintered wick with face-centred structure by the athermal Lattice Boltzmann
Method, 9th UK–Japan Seminar on Multi-Phase Flows 2013, London, UK, 2013.94) Yamaguchi, T., Wan, Q. and Yan, Y.Y., Numerical simulation of liquid-gas twophase-flow in sintered wick with face-centred structure by the athermal Lattice
Boltzmann Method, 13th UK Heat Transfer Confernece 2013, London, UK, 2013.9,UKHTC2013-1855) Yamaguchi, T., Wan, Q. and Yan, Y.Y., Numerical analysis of two-phase flow insintered copper wick by lattice Boltzmann method, The ASME 2013 11th
International Conference on Nanochannels, Microchannels, and Minichannels,
Sapporo, Japan, 2013.6, ICNMM2013-73205
6) Yamaguchi, T., Numerical Analysis of Bubbles Flow in 3D Sintered Wick byLattice Boltzmann Method, Invited presentation at International workshop on“Numerical heat and mass transfer from a view point of multiscale analysis”,
Nottingham, UK, 2013.5