[cig-commits] [commit] maint, williams/add-examples-grav2d: Modified the README to reflect the new layout of the examples. (3236f95)

[cig_noreply at geodynamics.org]

Repository : https://github.com/geodynamics/pylith

On branches: maint,williams/add-examples-grav2d
Link       : https://github.com/geodynamics/pylith/compare/f33c75b19fd60eedb2a3405db76a1fee333bb1d7...5b6d812b1612809fea3bd331c4e5af98c25a536a

>---------------------------------------------------------------

commit 3236f9513f27240455775ae850e7c3324660d012
Author: Charles Williams <C.Williams at gns.cri.nz>
Date:   Thu Jun 26 05:15:38 2014 +1200

    Modified the README to reflect the new layout of the examples.


>---------------------------------------------------------------

3236f9513f27240455775ae850e7c3324660d012
 examples/2d/gravity/README | 42 ++++++++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/examples/2d/gravity/README b/examples/2d/gravity/README
index 5f09daa..333edf3 100644
--- a/examples/2d/gravity/README
+++ b/examples/2d/gravity/README
@@ -1,9 +1,9 @@
-This set of example is meant to demonstrate the use of body forces and
+This set of examples is meant to demonstrate the use of body forces and
 initial stresses for a 2D problem. The example simply consists of an
 elastic block contained within a viscoelastic material of higher density.
 The surface of the block is coincident with the surface of the viscoelastic
 material initially. Depending on how we set up the problem, the elastic
-block will 'float' upwards due to the density contrast. There are 4
+block will 'float' upwards due to the density contrast. There are 7
 different simulations, which should generally be performed in order:
 
 1.  pylith grav_stress.cfg
@@ -15,29 +15,51 @@ different simulations, which should generally be performed in order:
     ./stress2spatialdb.py
 
 2.  pylith grav_stress_infin_is1.cfg
-    This will run a time-dependent simulation (200 years) that uses the
+    This will run a time-dependent simulation (100 years) that uses the
     initial stresses computed in step 1 to exactly balance the imposed
     gravitational body forces. Since the stresses are in equilibrium, no
     deformation should occur. This simulation uses the default infinitesimal
     strain formulation.
 
 3.  pylith grav_stress_infin_is2.cfg
-    This will run a time-dependent simulation (200 years) that uses initial
+    This will run a time-dependent simulation (100 years) that uses initial
     stresses computed assuming a constant density equivalent to the density
     of the viscoelastic material. The resulting stress state will reflect
     the density contrast between the block and the surrounding material.
     This simulation uses the default infinitesimal strain formulation.
 
-4.  pylith grav_stress_finite_is2.cfg
-    This will run a time-dependent simulation (200 years) that uses initial
+4.  pylith grav_stress_infin_is3.cfg
+    This simulation is identical to simulation #3, except that it uses a
+    smaller time step size and runs for a shorter period of time. For the
+    infinitesimal strain solution used here, this has no real effect on
+    the solution.
+
+5.  pylith grav_stress_finite_is1.cfg
+    This will run a time-dependent simulation (100 years) that uses the
+    initial stresses computed in step 1 to exactly balance the imposed
+    gravitational body forces. Since the stresses are in equilibrium, no
+    deformation should occur. This simulation uses a finite strain
+    formulation.
+
+6.  pylith grav_stress_finite_is2.cfg
+    This will run a time-dependent simulation (100 years) that uses initial
     stresses computed assuming a constant density equivalent to the density
     of the viscoelastic material. The resulting stress state will reflect
     the density contrast between the block and the surrounding material.
-    This simulation uses a finite strain formulation, and should thus
-    produce less vertical deformation that the infinitesimal strain version.
+    This simulation uses a finite strain formulation, but the solution is
+    unstable because the time step size is too large. The solution is
+    affected by the 'drunken sailor' instability. According to the Courant
+    condition described by Kaus et al. (PEPI, 2010), the time step size of
+    1.0 years is much too large.
+
+7.  pylith grav_stress_finite_is3.cfg
+    This simulation is identical to simulation #6, except that it uses a
+    time step size of 0.025 years rather than 1.0 years.  According to the
+    Courant condition described by Kaus et al. (PEPI, 2010), this time step
+    size is smaller than the stable time step size.
 
 The results of all the different simulations may be viewed using
 ParaView. We provide a ParaView state file (output/deform_view.pvsm),
 which you can load in ParaView to view the solution over the
-domain. The visualization is intended for steps 3 and 4 in which there
-is deformation.
+domain. The visualization is intended primarily for steps 3, 4, 6, and 7,
+in which there is significant deformation.