Presentation by Sylvain Charbonnier during the lunch & learn sessions on Day 2, June 25 at the EarthCube All-Hands Meeting

1. The flow simulation tools on
Vhub
Sylvain Charbonnier
Earthcube All-Hands Meeting
24-26 June 2014
VHub cyberinfrastructure for volcanology : Modeling, data sharing, and collaboration

2. The Energy Line Concept
• Energy Line concept (Hsu, 1975): A density flow initiated at some elevation will move as
potential energy is converted to kinetic energy minus friction.
• The energy line is the slope along which the frictional loss is balanced by conversion of
potential to kinetic energy.
• If the topographic slope is greater than the energy line, the flow will decelerate. The flow
comes to rest where the energy line intersects the topographic surface.

3. • The slope of the energy line (α) is calculated as the arc tan of the loss in height (H) divided
by run-out distance (L).” (Sheridan, 1979):
The Energy Line Concept
H/L = μ = tan α
Driving acceleration = g sin α;
Retardation = μ g cos α
Δv/ Δt = a = g sin α - g μ cos α = g (sin α - μ cos α )

4. The Energy Cone Model
• By using digital topographic models of volcanoes, the energy-line model was expanded
into a three dimensional representation called the “energy-cone” model by sweeping
the energy line through a 360° arc (Malin and Sheridan, 1982; Sheridan and Malin,
1983).
• These friction models are equivalent to sliding-block models, and are thought to
potentially apply to virtually all types of pyroclastic density currents (Sheridan, 1979).
• They assume straight-line flow
trajectories that pass through
topographic obstacles, encompass
the entire cone and ignore
confining topography.
• The energy cone model is the only
model that can reasonably be used
to simulate dilute pyroclastic
density currents such as surges…

6. There are five input parameters:
1. DEM (in .txt format)
2. H/L
3. Source Altitude (always higher than
the highest point)
4. Longitude (in degrees if a kmz is
desire, UTM can be used as well but
only a jpg will be created)
5. Latitude (in degrees if a kmz is
desire, UTM can be used as well but
only a jpg will be created)

7. What is Titan2D?
 Titan2D is a freely available computer program developed by the GMFG group at SUNY
Buffalo (USA) for the purpose of simulating dry granular avalanches over digital elevation
models of natural terrain.
 The program is designed for simulating geological mass flows such as debris avalanches,
landslides and some dense volcanic flows.
 Titan2D can be run on laptops to supercomputers as a standalone version on any linux
platforms and/or directly online at https://vhub.org/tools/titan2d.
2002 Pink Mountain landslide,
British Columbia, Canada
2006 Merapi
Block-And-Ash flow, Java,
Indonesia
1997 Mt Adams debris
avalanche, Washington,
USA

8. Inside Titan2D…
• New class of geophysical mass flow models (Savage and Hutter, 1989)
→ depth-averaged granular-flow model on 3D terrain (Iverson and Denlinger, 2001)
• conservation equations for mass (3) and momentum (4 and 5) → « shallow-
water » model with a Mohr-Coulomb frictional resistance term
• The flowing mass → incompressible continuum with constant density
Patra, A.K., Bauer, A.C., Nichita, C.C., Pitman, E.B., Sheridan, M.F., Bursik, M.I., Rupp, B., Webber, A., Stinton, A.J.,
Namikawa, L.M., Renschler, C.S., 2005. Parallel adaptive simulation of dry avalanches over natural terrain. J. Volcanol.
Geotherm. Res. 139, 1-22.

9. Model Applications
• Hazard assessment:
 If a mass flow were to be initiated at a particular location, what areas are
most at risk from that flow?
 What is the probability that flow depth at a particular location will exceed
a given threshold value?
Model Verification and Validation:
 Verification is a process of identifying “to what degree” a given
mathematical model is numerically solved correctly.
 Validation attempts to check computational results against reality
(experiments and/or actual events) → back analyses
variability and frequent disparity between data sets of modeled flows
and field observations.

10. Titan2D on VHub
 Titan2D toolkit already installed and ready to use at https://vhub.org/tools/titan2d
 New Java based Graphical User Interface as of June 6th 2011 including all latest stand-
alone additional features (flux sources, material map, volume calc., etc…)
 New adaptive visualization platform for displaying the different results over a 3D shaded
relief Digital Elevation Model + Google Earth!!!

11. Titan2D tutorial on VHub
 Titan2D tutorial available to download at https://vhub.org/resources/761
 During this tutorial, we will go through a stock example and:
(1) learn how to enter the different input parameters for running a Titan2D simulation;
(2) run the simulation and;
(3) visualize the results using the Titan2D Vhub viewer.
 We will run a second simulation by changing only one parameter and investigate the
effects on the simulated flow through a direct comparison of the results.

12. Load/Save Tab

13. Geographic Information System Tab

14. General Tab

15. Material Map Tab
 The internal friction angle ϕint, is the steepest angle that the upper surface of a conical pile
of dry sand can make with respect to the horizontal plane it is resting on.
 The bed (also known as basal) friction angle, ϕbed, is the angle that a plane needs to be
inclined so that a block of material will slide downslope at a constant speed.

16. Piles Tab
Minor extent
Major extent
Orientation angle
0°
0°
Initial direction
Titan2D Pile geometry in map view:

17. Job submission Tab

18. Job monitor Tab 1

19. Job monitor Tab 2

20. Google Earth Outputs

21. Google Earth Outputs

22. Google Earth Outputs

23. PARAVIEW
• Using the Vhub workspace
tool, download the entire
Titan2d simulation folder
from your Vhub storage
into your computer
• Open Paraview and open
the xdmf0000000000.xmf
file from your Titan2d
simulation folder and play
with the options…
• Download and install on your computer the last version of Paraview software at
http://www.paraview.org/paraview/resources/software.php

24. ArcGIS
• Using the Vhub workspace tool, download
the ‘pileheightrecord’ file from the Titan2d
simulation folder into your computer
• Open the file using a text editor and replace
the file header to match the ArcInfo header
format (ncols, nrows, xllcorner, yllcorner,
cellsize, nodata_value). Save it with a new
name and .asc file extension.
• Open ArcGIS, convert the ascii file into a
raster, flip it and georeferenced it using the
X and Y boundary coordinates from the
original ‘pileheightrecord’ file header...

25. Titan2D Viewer

26. Titan2D Viewer

27. Titan2D Viewer

28. Titan2D Viewer

29. Titan2D Viewer

30. Questions?