Types of Simulations#
PyLith currently supports two types of problems:
Time dependent, and
Static Green’s functions.
Time-Dependent Problem (TimeDependent)#
This type of problem solves a time-dependent boundary value problem and applies to static, quasistatic, and dynamic simulations. We use the PETSc object to manage the time-stepping, including the selection of the time-stepping algorithm. By default PyLith uses the backward Euler time-stepping algorithm.
Pyre User Interface
See TimeDependent Component for Pyre properties and facilities and configuration examples.
Initial Conditions#
Note
New in v3.0.0.
The initial conditions for a simulation are specified via a combination of initial values for the solution and initial values for state variables. The initial values for state variables are specified via the spatial databases for the auxiliary field of each material. In this section we discuss how to set the initial values of the solution field.
InitialConditionDomain#
We use this object when we want to specify the initial values of solution subfields across the entire domain using a single spatial database.
Pyre User Interface
See InitialConditionDomain Component for Pyre properties and facilities and configuration examples.
InitialConditionPatch#
We use this object when we want to specify the initial values of solution subfields across patches of the domain defined by materials.
Important
Initial conditions over a patch currently only work for Gmsh input files. Exodus II files from Cubit do not contain the information needed by the current PyLith implementation.
In creating the physical group in Gmsh, you must include the cells and all lower dimension entities (faces, edges, and vertices).
The easiest way to do this is to use the VertexGroup provided in the pylith.meshio.gmsh_utils Python module.
By default, the lower dimension entities will be included in the physical group.
Pyre User Interface
See InitialConditionPatch Component for Pyre properties and facilities and configuration examples.
Numerical Damping in Explicit Time Stepping#
Danger
Not yet reimplemented in v3.x.
Green’s Functions Problem (GreensFns)#
This type of problem applies to computing static Green’s functions for elastic deformation.
The GreensFns problem loops over a suite of fault slip impulses and computes the static solution for each impulse using the linear solver.
In the output files, the deformation at each “time step” is the deformation for a different slip impulse.
The fault slip impulses are specified using FaultCohesiveImpulses for the fault.
See Fault Slip Impulses (FaultCohesiveImpulses) for more information.
Warning
The GreensFns problem generates slip impulses on a fault.
PyLith currently requires that impulses be applied to a single fault of type FaultCohesiveImpulses.
Pyre User Interface
See GreensFns Component for Pyre properties and facilities and configuration examples.