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Updated - April 13, 2021 -

Hobby (Music) => Click!

News !

April 8, 2021
I opened Lab. Website (tentative).
I also movies on my YouTube channel.

April 1, 2021
I have become a Full Professor of Tohoku University.

February 23, 2021
I opened my YouTube channel "Plasma Fluid Mechanics".
I would be happy if you subsribe it and click Like buttons.


I N D E X
 

Click the movie to play.

Three-dimensional flow dynamics of a DC-RF hybrid thermal plasma

A strong and useful plasma field is obtained by combining a radio-frequency (RF) inductively coupled thermal plasma and a non-transferred direct current (DC) thermal plasma jet. However, a thermal plasma is a unique fluid with intense light emission, high temperature (over 10,000 K), a complicated flow caused by electromagnetic forces and thermal expansion. This feature prevents direct measurements in experiments; therefore, the details of the thermofluid field are still poorly understood.

A time-dependent 3-D simulation based on magnetohydrodynamics (MHD) has been attempted to clarify the thermofluid field of the plasma, which is governed by the conservation equations of mass, momentum (Navier-Stokes) and energy coupled with the electromagnetic equations (Maxwell). Simultaneously, the simulation takes account of the temperature-dependent large variations of the thermodynamic and transport properties as a plasma "fluid".

The movies show the dynamic behaviors of the thermofluid field and the vortex structure interacting with the electromangeitc field. The colors indicate the temperatures. Such a complicated flow has been predicted from experimental studies; however, it has never been obtained by any axisymmetric 2-D simulations which have been carried out.

The present time-dependent 3-D simulation has first successfully obtained these realistic results and revealed the plasma flow dynamics.   (Note: Some careful treatments are required to capture vortex structures of thermal plasma flows by numerical simulation. See the next section.)

For more information, please see ...
  • Three-dimensional flow dynamics of an argon RF plasma with DC jet assistance: a numerical study,
    Journal of Physics D: Applied Physics, Vol. 46, No. 1, (January, 2013) 015401 (12 pages).
    Masaya Shigeta
  • Time-Dependent 3-D Simulation of an Argon RF Inductively Coupled Thermal Plasma,
    Plasma Sources Science and Technology, Vol. 21, No. 5, (October, 2012), pp. 055029 (14 pages).
    Masaya Shigeta
  • Turbulence modelling of thermal plasma flows,
    Journal of Physics D: Applied Physics, Vol. 49, No. 49, (November 9, 2016), pp. 493001 (18 pages).
    Masaya Shigeta


  •  

    Click the movie to play.

    Fundamental problem in numerical simulation of thermal plasmas

      

    As mentioned the above section, simulation of thermal plasma is generally difficult. The entire flow field, in which the plasma at a high temperature and a cold gas at room temperature co-exist, must be treated simultaneously. Widely varied temperatures of 300-12,000 K cause large variations of the transport properties and the density. Meanwhile, the Mach numbers are very small in and around the plasma. Consequently, when a numerical method for a compressible flow simulation is used, the computation takes an extremely long time to obtain a numerical solution for a practical time scale. Therefore, a thermal plasma is treated as an incompressible flow with the density as a temperatur-edependent variable. This condition, which is severe for numerical flow simulations, usually destabilizes the computation (= the computation easily breaks down). That is why thermal plasma simulations have often used differencing schemes which suppress numerical instability effectively. However, those schemes also suppress the actual physical instability simultaneously. In consequence, the numerical result does not simulate any realistic flow with vortices as shown in Left figure. On the other hand, schemes that are effective for vortex capturing often cause destabilization of computations. Although these two aspects mutually conflict, thermal plasma flows should also be calculated as "simulation" somehow using such schemes to obtain realistic results. As a result, the effort gives a more realistic flow as shown in Right figure.

    An experiment visualized that a thermal plasma jet entrained surrounding cold gas by Kelvin-Helmholtz instability about 30 years ago. Nevertheless, such a flow had never been simulated because of the numerically severe conditions. Overcoming the difficulties, the present effort broke through that problem and obtaiend a successful result.

    For more information, see ...
  • Turbulence modelling of thermal plasma flows,
      Journal of Physics D: Applied Physics, Vol. 49, No. 49, (November, 2016), pp. 493001 (18 pages).
      Masaya Shigeta
  • Modeling and Simulation of a Turbulent-like Thermal Plasma Jet for Nanopowder Production,
    IEEJ Transactions on Electrical and Electronic Engineering, Vol. 14, (January 1, 2019), pp. 16-28.
    Masaya Shigeta
  • Simulating Turbulent Thermal Plasma Flows for Nanopowder Fabrication,
    Plasma Chemistry and Plasma Processing, Vol. 40, Issue 3, (May 1, 2020), pp. 775-794.
    Masaya Shigeta


    [ New!! ] 3D simulation => Click!

  •  


    Simple equations to describe aerosol growth

     
              often-used equations of moments                      our new equations

    Both sets of equations give almost the same results for the time evolutions of the particle number density and mean size of aerosol.

    Aerosol growth through nucleation, condensation/evaporation and coagulation has usually been described by the simultaneous equations of the moments of the particle size distribution function (PSDF) with its profile assumption (Left) in numerical calculations. This method solves the four complex ordinary differential equations.

    For this problem, we derived a set of two ordinary differential equations and one algebraic equation (Right) without any profile assumption for the PSDF. In spite of its much simpler formulation and lower computational costs, it gives reasonable a numerical result which is almost the same as that obtained with a more complex set of equations (Left).

    This mathematical model can be expected to be applied to numerical predictions for not only plasma-aided nanopowder syntheses but also water-droplet generation in a steam turbine (causing erosion), meteorological problems with cloud/fog generation, space design requiring humidity control, etc.

    Note that the paper below presents the sets of equations applicable to the continuum size regime as well as the free molecular size regime shown above.

    For more information, see ...
  • Simple equations to describe aerosol growth,
      Modelling and Simulation in Materials Science and Engineering, Vol. 20, No. 4, (May, 2012), pp. 045017 (11 pages).
      Valerian A. Nemchinsky and Masaya Shigeta
  • Modeling and Simulation of a Turbulent-like Thermal Plasma Jet for Nanopowder Production,
    IEEJ Transactions on Electrical and Electronic Engineering, Vol. 14, (January 1, 2019), pp. 16-28.
    Masaya Shigeta
  • Simulating Turbulent Thermal Plasma Flows for Nanopowder Fabrication,
    Plasma Chemistry and Plasma Processing, Vol. 40, Issue 3, (May 1, 2020), pp. 775-794.
    Masaya Shigeta


    [ New!! ] 3D simulation => Click!

  •  

    Click the movie to play.

    Collective growth of silicide nanoparticles (nanopowder) in thermal plasma synthesis

    These movies show the time evolutions of the particle size-composition distributions of the silicide (metal-silicon intermetallic compound) nanoparticles (nanopowder) synthesized in thermal plasma processing.

    We have successfully clarified the formation mechanisms including binary nucleation and binary co-condensation of two components (Mo&Si, Co&Si, etc.) by our original mathematical model and solution algorithm "Two-Directional Nodal Method".

    In Mo-Si system (Initial vapor ratio Mo:Si = 1:1), the molybdenum-rich nanoparticles first grow up and subsequently silicon condenses on the nanoparticles, which results in the significant growth of the nanopowder.
    On the other hand, in Co-Si system (Initial vapor ratio Co:Si = 1:1), silicon-rich nuclei are first generated and immediately make a rapid growth into nanoparticles due to simultaneous co-condensation of cobalt and silicon.

    These results show that the nanopowders synthesized in thermal plasma processing have widely ranging sizes and compositions inevitably even under a simple condition (Initial vapor ratio Metal:Si = 1:1).

    These numerical results agree with the experiment results, which endorses the validity of our model.

    In addition to molybdenum-silicide (Mo-Si) and cobalt-silicide (Co-Si), the nanoparitcles' formation mechanisms are being studied for titanium-silicide (Ti-Si), iron-silicide (Fe-Si), borides (boron-based intermetallic compound), and magnetic alloys (Fe-Co, Fe-Nd etc.).

    For more information, see ...
  • Growth model of binary alloy nanopowders for thermal plasma synthesis,
      Journal of Applied Physics, Vol. 108, Issue 4, (August, 2010), pp. 043306 (15 pages).
      Masaya Shigeta and Takayuki Watanabe
  • Effect of precursor fraction on silicide nanopowder growth under thermal plasma conditions: a computational study,
      Powder Technology, Vol. 288, (January 1, 2016), pp. 191-201.
      Masaya Shigeta, Takayuki Watanabe
  • Effect of Saturation Pressure Difference on Metal-Silicide Nanopowder Formation in Thermal Plasma Fabrication,
      Nanomaterials, Vol. 6, (March 7, 2016), pp. 43 (10 pages). (Impact factor = 3.553, 5-year impact factor = 4.100)
      Masaya Shigeta, Takayuki Watanabe


  •  

    Click the movie to play.

    Radio-frequency inductively coupled thermal plasma flow
    & nanoparticle formation with counterflow cooling

    It is possible to mass-produce nanoparticles by quenching a thermal plasma flow including material vapor (here, platinum vapor) with counterflow cooling promoting nucleation. These numerical results can be obtained by solving the mathematical models coupling the sequential physics of a plasma flow dynamics, material vaporization, and nanopowder growth.

    Nanoparticles are created through homogeneous nucleation and subsequent heterogeneous condensation growth. The nanoparticles simultaneously grow up by Brownian coagulation between themselves. However, it is still impossible to calculate this collective growth of many nanoparticles for a practical time scale by the "Molecular dynamics" approach even with powerful computers. Meanwhile, an "Aerosol dynamics" equation effectively expresses the growth. Although the equation cannot be solved even numerically yet, it can be calculated by combining with a statistical method. In addition, the calculation also takes into account diffusion, thermophoresis, and convection of nanoparticles as well as transport of material vapor.

    Many nuclei are generated at the interface between the plasma flow and the counterflow. Being transported downstream, the nuclei grow up into nanoparticles gaining the material vapor. The nanoparticles also increase their sizes by coagulation with each other, and consequently the number of nanoparticles decreases.

    For more information, see ...
  • Numerical investigation of cooling effect on platinum nanoparticle formation in inductively coupled thermal plasmas,
    Journal of Applied Physics, Vol. 103, Issue 7, (April, 2008), pp. 074903 (15 pages).
    Masaya Shigeta and Takayuki Watanabe
  • Two-dimensional analysis of nanoparticle formation in induction thermal plasmas with counterflow cooling,
    Thin Solid Films, Vol. 516. (May, 2008), pp. 4415-4422.
    Masaya Shigeta and Takayuki Watanabe
  • Model Integration for Metal Nanoparticle Synthesis by an RF Thermal Plasma Flow with Counterflow Cooling,
    Transactions of the Japan Society of Mechanical Engineers, Vol. 75, No. 758, (October, 2009), pp. 2019-2028. (in Japanese)
    Masaya Shigeta and Takayuki Watanabe



  • @

    Click the movie to play.

    Arc plasma dynamics in a TIG welding condition

    This movie shows a simulation result of arc plasma in a TIG welding condition.

    The arc plasma has Max. temperature ~18000 K and Max. speed ~200 m/s beneath the electrode tip.
    However, their positions do not coincide. It is also interesting that the sizes of the high-temperature region and the high-speed region are different.

    The shielding gas supplied from the top is entrained partially into arc plasma, ionized, and then becomes arc plasma. The high-temperature region is almost stationary whereas the low-to-middle-temperature region fluctuates by fluid dynamic instability.

    For more information, see ...
  • Numerical analysis of correlation between arc plasma fluctuation and nanoparticle growth-transport under atmospheric pressure,
    @Nanomaterials, Vol. 9, No. 12, (December 6, 2019), pp. 1736 (13 pages). (OPEN ACCESS)
    @Masaya Shigeta, Manabu Tanaka, Emanuele Ghedini



  • @

    Click the movie to play.

    Dynamics of two non-neutral plasma rings in a uniform magnetic field

    A dynamic motion of two non-neutral plasma rings in a uniform magnetic field was simulated using a discrete vortex method with a symplectic integrator. Finite Larmor radius effect and Transient electric field effect were taken into account as well. Here, electron plasma or positron plasma was supposed as a non-neutral plasma. Colors indicate the speeds in each system. (Movie loops 3 times.)




    News !

    April 1, 2021
    I have become a Full Professor of Tohoku University.

    April 1, 2021
    I have become a Committee member on Plasma Science for Materials, Japan Society for the Promotion of Science (JSPS) 153 Committee.

    April 1, 2021
    I have become a Delegated member of the Japan Society of Fluid Mechanics.

    March 16, 2021
    I had an Invited talk at the 68th JSAP Spring Meeting 2021, Division of Plasma Electronics 30th Anniversary Special Session.

    February 23, 2021
    I opened my YouTube channel "Plasma Fluid Mechanics".
    I would be happy if you subsribe it and click Like buttons.

    November 3, 2020
    I had an Invited talk at 7th Plasma Science & Entrepreneurship workshop.

    August 6, 2020
    Lecture on Photron Web Seminar "Leading Edge of Welding Visualization by JWRI Osaka University!
    - Hybrid Lecture of Welding Visualization by Hi-Speed Video and Numerical Simulation -
    " was finished successfully.
    I thank the staffs and 540 attendees!!

    Juanuary 14, 2020
    Web Manga (Catoon) "What is usage of welding process simulation?" has been released. (Free Access)

    Juanuary 11, 2020
    My 5th Invited Review Paper has been published in Plasma Chemistry and Plasma Processing.

    Juanuary 1, 2020
    I was assigned to be a member of Board of Directors on International Plasma Chemistry Society.

    Juanuary 1, 2020
    My 4th Invited Review Paper has been published in Japanese Journal of Applied Physics.

    December 17, 2019
    We have received Power Academy Grant.

    December 12, 2019
    My article has been released from NIKKAN KOGYO SHINBUN.

    December 6, 2019
    Our paper has been published in Nanomaterials (IF = 4.034). (OPEN ACCESS)

    August 6, 2019
    We received Awards for Encouragement of Welding Physics and Technology for two different studies.

    June 13, 2019
    I was elected as a member of Board of Directors (Jan. 2020 -) on International Plasma Chemistry Society.

    June 11, 2019
    I had an Invited talk at ISPC24.

    May 10-11, 2019
    I had an intensive seminar at Department of Chemical Engineering, Graduate School of Kyushu University as a part-time professor.

    March 21, 2019
    I had an Invited talk at ISPlasma2019/IC-PLANTS2019.

    January 17, 2019
    I received Award of Plasma Science for Materials.

    December 27, 2018
    My 3rd Invited Review Paper has been published in IEEJ.

    August 3, 2018
    We received Award of Welding Arc Physics.

    June 6, 2018
    I had an Invited talk at ICPP2018 held in Vancouver, Canada.

    June 5, 2018
    We received Award for Excellent Treatise, Japan Light Metal Welding Association.

    November 21, 2017
    I received OSAKA UNIVERSITY AWARD (Young Professor Section).

    June 30, 2017
    I had an Invited talk at Int. Symp. of IIW2017 held in Shanghai, China.

    May 13, 2017
    I had an Invited talk at EMN2017 on nanoparticles held in San Sebastian, Spain.

    November 9, 2016
    My Topical Review (Invited) has been published on Journal of Physics D: Applied Physics.

    August 10, 2016
    We received Best Paper Award for Thermal Engineering.

    August 2, 2016
    We received Award for Encouragement of Welding Physics and Technology.

    July 4, 2016
    I had an Invited talk at HTPP 14 held in Munich, Germany.

    April 13, 2016
    We received Best Paper Award of Japan Welding Society.

    March 28, 2016
    I attended the M6 meeting of "Nanodome" in EU's international project "Horizon 2020" as a member of External Advisory Board.

    January 19, 2016
    I had an Invited talk at ISN2A 2016 held in Caparica, Portugal.

    December 10, 2015
    I had an Invited talk at International Symposium C5 in MRS-J 2015.

    October 14, 2015
    I had an Invited talk at ICRP-9/GEC-68/SPP-33 sponsored by The Japan Society of Applied Physics & American Physical Society.

    August 4, 2015
    We received Award of Welding Arc Physics.

    July 22-23, 2015
    I had a lecture at Kyushu University.
    Title: Fundamentals and Applications of Computational Plasma Fluid Mechanics

    July 14, 2015
    I received Osaka University Presidential Award for Encouragement.

    May 29, 2015
    I had a Special lecture at Directors Meeting of Kansai Branch, Japan Welding Society.

    November 1, 2014
    I had a Plenary lecture at Japan Society of Mechanical Engineers, Kansai Branch, 15th Autumn Forum.

    October 10, 2014
    I had an invited talk at 81st Meeting for Japan Welding Society, Tokai Branch & Japan Thermal Spray Society, Chubu Branch.

    September 9, 2014
    I received Award for Encouragement of Research in The IUMRS International Conference in Asia 2014 (IUMRS-ICA 2014).

    July 29, 2014
    I had an invited talk at Gordon Research Conference (GRC), Plasma Processing Science, Smithfield (RI), USA.

    June 11, 2014
    I had an invited talk at International Conference on Microelectronics and Plasma Technology 2014 (ICMAP2014), Gunsan, Korea.

    June 4, 2014
    I had an invited talk at JWRI-KMUTT Workshop, Bangkok, Thailand.

    May 14, 2014
    I had an invited talk at Japan-Indonesia Welding Seminar 2014, Jakarta, Indonesia.

    April 15, 2014
    I received The Young Scientists' Prize, the Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology.

    March 3, 2014
    I had a Review talk at 4th International Round Table on Thermal Plasmas for Industrial Applications: Challenges and Opportunities.

    December 10, 2013
    I had an invited talk at 23rd Annual Meeting of MRS-Japan.

    November 27, 2013
    I had an invited talk at 3rd China-Japan Workshop on Welding Thermo-Physics.

    August 1, 2013
    I have moved to Osaka University as an Associate Professor.

    July 17, 2013
    I had an invited talk at 31st International Conference on Phenomena in Ionized Gases (ICPIG-31).

    March 6, 2013
    I had an invited talk at Hokuriku Branch Symposium 2013 of The Institute of Electrical Engineers of Japan.

    February 21, 2013
    Demonstration of dynamics of two non-neutral plasma rings in a unifrom magnetic field was added.

    January 6, 2013
    The explanation of simple equations to describe aerosol growth was added.

    January 3, 2013
    The explanations and animations of thermal plasma simulation were added.

    January 1, 2013
    The figure of vortex structure in my paper was adopted as the cover image of Journal of Physics D: Applied Physics, Vol.46, No.1.

    December 1, 2012
    I have come back from USA.

    November 30, 2012
    My paper "Three-dimensional flow dynamics of an argon RF plasma with DC jet assistance: a numerical study" has been published
    in Journal of Physics D: Applied Physics.

    October 3, 2012
    My paper "Time-Dependent 3-D Simulation of an Argon RF Inductively Coupled Thermal Plasma" has been published
    in Plasma Sources Science and Technology.

    September 30, 2012
    I have come to USA.

    June 29, 2012
    I had an invited talk at the 12th European Plasma Conference, High-Tech Plasma Processes (HTPP-12) which was held in Bologna, Italy.

    June 14, 2012
    I was invited to Celebratory reception to mark the 10th anniversary of the IOP Publishing Editorial Office in Japan at British Embassy Tokyo.
    because our collaborative review article with Dr. Murphy of CSIRO (Australia) is included in a collection of the most frequently downloaded papers published in 2011.
    (See also the section of "Journal of Physics D: Applied Physics" on this page.)

    May 28, 2012
    Our collaborative paper with Prof. Nemchinsky of Keiser University (USA) has been published in Modelling and Simulation in Materials Science and Engineering (IOP publishing).

    March 1, 2012
    Our collaborative paper with Prof. Colombo, Prof. Ghedini, Dr. Sanibondi and Mr. Gherardi of University of Bologna (Italy) has been published in Plasma Sources Science and Technology (IOP publishing).

    February 15, 2012
    Our collaborative paper with Prof. Watanabe, Dr. Choi and Ms. Cheng of Tokyo Institute of Technology has been published in Chemical Engineering Journal (Elsevier).

    November 21, 2011
    Web page of Plasma Research Group at University of Bologna is added on links.

    October 5, 7, 2011
    I gave two lectures at University of Bologna, Italy.

    August 17, 2011
    Our review article "Thermal plasmas for nanofabrication" (Invited paper) has been downloaded
    500 times for 4 months! = 3% of articles across all IOP journals!

    April 15, 2011
    Our review article "Thermal plasmas for nanofabrication" (Invited paper) has been published
    in Journal of Physics D: Applied Physics (Special issue on perspectives in plasma nanoscience).
    ( to see the quick review on IOP science -> Click! )

    March 11, 2011
    An incredible earthquake hit us.

    December 13, 2010
    I gave an invited talk at Second International Symposium on Plasma Nanoscience (iPlasmaNano-II) in Australia.

    November 11, 2010
    We won Best Paper Award at the International Symposium on Visualization
    in Joining & Welding Science through Advanced Measurements and Simulation.

    October 27, 2010
    I gave an invited talk at 2010 Workshop for Preparation of Nanoparticles by Thermal Plasmas in Korea.

    September 1, 2010
    An edited book "Nanomaterials: Properties, Preparation and Processes"
    has been published by NOVA Science Publishers, Inc. (New York).
    We wrote Chapter 3: Nanoparticle Synthesis by Thermal Plasmas.

    August 23, 2010
    Our original paper "Growth model of binary alloy nanopowders for thermal plasma synthesis"
    has been published in Journal of Applied Physics.

    July 23, 2010
    I gave an invited talk at the 97th Meeting of the 153rd Committee on Plasma Materials Science,
    the Japan Society of Applied Physics.

    April 13, 2010
    I gave an invited talk at WORKSHOP ON INDUSTRIAL APPLICATIONS OF THERMAL PLASMAS in Italy.


    © 2004- Masaya SHIGETA