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The ultimate website for understanding granular flows

Welcome to &

[Mt. Pinatubo coignimbrite ash cloud on the morning of June 15, 1991. Courtesy of Robert LaPointe.]

You may ask why two Domain Names for the same website … Well, it has been agreed between (Chuo University, Japan) and  to share the use of "" and its webmaster solely develops the website, while "" guarantees that the Domain Name "" remains a granular-aimed project and a non-commercial, scientific, educational website opened to anyone. I, the webmaster, fully agree with these objectives of developing an always better and more opened granular-website for the geophysical and granular scientific communities, students, and any curious amateur.

Granular-Volcano-Group has been on the web since December 2000, and has now reached the critical mass of being a truly comprehensive website on granular-matter, granular-flows and fluid dynamics. Its goals are: 

1- To present some of the state-of-art and most recent research currently developed in the fields of granular-matter and granular-flows in physics, geophysics, and volcanology. This includes: (i) computer modeling of granular gravity current flows, (ii) rheology of the granular-matter, (iii) grain-size analysis of pyroclastic flows commonly seen in volcanology (can we relate grain-size properties of a set of grains to the physical processes that have formed, moved and settled them), (iv) explain fluid-dynamic concepts in simple but accurate ways;

2- Volcanology and granular-sciences must be fun and for everyone, no matter what your scientific background is! So, theoretical research should not rhymed with "secret and highly-classified research" as it should be accessed by whomever is interested in granular-flows in geophysics and volcanology. Hence, we’d like to promote a permanent interaction between the general public and scientists.

The least you know the more you are welcomed here !

If you wanna join this "granular web team", if you have the least idea you want to share, or if you have any suggestion, please feel free to email the webmaster.

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You will find here many useful theoretical information. It took me months of hard labor to write those equations, figures, understandings many challenging theoretical concepts, and many other months of programming efforts. Please, have some respects for my own work, sweat and hard labor: if you want to copy from here, just email me.

If you need an official reference for the content of this website, please, use:
Dartevelle, S., Numerical and granulometric approaches to geophysical granular flows, Ph.D. thesis, Michigan Technological University, Department of Geological and Mining Engineering, Houghton, Michigan, July 2003.

I would truly appreciate to hear from you. This website is here because of you and your visit. Why should I bother to spend so much time to develop this website and to pay more than $200/year if people just come, help themselves and silently leave it? This website is not here by an act of God. It is here because I want it to be and because I want the Web and Science based on openness, freedom, and sharing principles. Don’t be a silent visitor, let me know what you think of this place, let me know how I can build an even better website, where I failed and where I succeeded. In other words *share* your ideas, knowledge and opinions. This is not for me but for *all* of us and our Web community’s sake. The least you can do is to sign the Granular-Volcano Guestbook, share your ideas in the Granular-Volcano Discussion Forum, and/or email me.

Thanks and enjoy the visit!

The WebMaster,
Sébastien Dartevelle

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September 15, 2003: I have update the whole website and corrected of a few minor typos within the text and the equations. Supplementary explanations have been added in the All I wanna know about viscous stress! webpage in order to highlight and clarify the concept of viscosity within the plasticity theory (for frictional granular flows).

March 15, 2003: New computer simulation movies of plinian clouds have been added in our numerical results page. In addition, I have created a Power Point slide show of plinian cloud simulations, with supplementary explanations, simulations, movies, and validation studies (see the plinian cloud simulation page).

July 26, 2002: We are very honored that the American Association for the Advancement of Science (AAAS) and the prestigious magazine SCIENCE have elected our website as the best Granular Resource of the web:

"Totally Granular"

"Much of what spews from the maw of a volcano, such as clouds of ash or streams of sizzling muck, qualifies as a granular flow, a mixture of fine particles swept along by a fluid such as water or air. The Web site Granular Volcano Group provides an introduction to the physics of these mixtures written by Sébastien Dartevelle, a Ph.D. student at Michigan Technological University in Houghton. The details of granular flow get hairy because the fluid and the particles are in different phases, so the equation-laden site is not for the math-phobic or physics-averse. Sections cover topics such as viscosity within a stream of particles, friction between grains, and models of granular flows. You can also watch movies of supercomputer simulations of various kinds of gas clouds and debris flows."

Science, vol. 297, 26 July 2002, pg. 483. [Click Here for the PDF version of this article].

[Mt. Pinatubo plinian cloud. June 1991, Philippines. Courtesy of USGS.]

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For now, please, feel free to visit the computational and theoretical pages throughout this website:

Main Granular Volcano Group Webpages:

- What is a Granular Medium?

A complete review of Plastic-Frictional theories:

   - Part 1. Introduction: Mohr-Coulomb and von Mises Stresses, a warm-up

   - Part 2. Plastic Potential Theory, a review

   - Part 3. Critical State Theory, a review

   - Part 4. Constitutive Equations for frictional granular flow

- All I wanna know about viscous stress!

- Granular Theory: an Overview

- Compute Your Own Atmospheric Profile

Numerical Results:

   - Go to the Numerical Results Page (Introduction and all Results)

   - Go to the Plinian Cloud Simulations Page

Home Page

You may also enjoy those pages:

| Guestbook | Discussion Forum | Chatroom | Volcano Links | Granular Links | Awards | Logos | Who is the Webmaster? | Ph.D. |

[Pyroclastic flow flowing downslope. Montserrat Island, Caraibes. Courtesy of Dr. Marco Fulle]

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I, the webmaster of "" and "", wish to thank Prof. Y-h. Taguchi for allowing me to use the Domain Name "". & are copyrighted Domain Names. The contents of this website are copyrighted.

I also wish to thank the National Energy Technology Laboratory (NETL), division of the U.S. Department of Energy (DOE) for allowing me to use their multiphase flow supercomputer codes (MFIX). I am particularly grateful to Dr. Thomas O’Brien, Dr. Madhava Syamlal, and Dr. Sreekanth Pannala for their continuous supports, helps and advice. The existence of this whole project would not have been possible without them. Please, visit the MFIX page for further details regarding the supercomputer codes used in this project.

The National Science Foundation (NSF), the Michigan Technological University (MTU), and McGill University are acknowledged for their financial, administrative, and scientific supports. I am grateful to Prof. W.I.Rose (MTU) and Prof. J.Stix (McGill) for their trust and support in my PhD project.

Please, before you continue your visit throughout this website, you must be aware that it uses Java Scripts, DHTML, Applets Java, Cascading Style Sheet (css) features, and Movie animations in format AVI (compression Indeo and Cinepak).

Some pages have a lot of equations and mathematical symbols, they make take a few seconds to upload depending on your browser version, your connection to the internet, your modem, so forth. Please, be patient. It may be useful from time to time to reload your page.

This website work fine as long as you use the latest Browser version. Please, make sure to use Ms. Internet Explorer 6.0, Netscape Navigator 6.22, or Mozilla 1.0 (or any later version of those browsers).

Opera Browser cannot operate through this website as it cannot handle Dynamic-HTML.

If you have received an "alert message" regarding the version of the Browser you are currently using, please, download for free the latest Browser version: Ms. Internet Explorer, Netscape Navigator, and/or Mozilla Browser.

If you aren’t sure of what your current browser settings are, GO to the computer scan page.

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Any problems or comments with this web site can be reported to the Volcano Web Master.