Frequently Asked Questions
If you want to develop your own simulation workflow or develop new code we also suggest to have a look at the code examples provided in the runScripts directory.
Can the spatial resolution of simulations performed with com1DFA (dense flow) be changed?
The default setup of
com1DFA is calibrated for medium to large dense flow snow avalanches in regards to hazard
mapping. To provide calibrated results, new simulations with DEM cell sizes other than 5 meters are being
remeshed by com1DFA to 5 meters for computation.
It is possible to change the cell size, but keep in mind there are no tested/calibrated setups available. We want to list a few things that we strongly suggest to take into account when changing the mesh cell size:
Start by changing the meshCellSize in the configuration file of
com1DFACfg.inior rather your local copy of it), and consider changing the sphKernelRadius to match the new mesh cell size.
For the SPH gradient, required to compute the lateral forces, the number of particles per cell has to be adjusted. If the sphKernelRadius (see first point) is decreased, the number of particles should increase to ensure a reasonable estimate of the gradient. There are three options for setting the number of particles which is computing from the mass per particle (massPerParticleDeterminationMethod; see Initialize particles):
With the default setup MPPDH (mass per particle through release thickness), the number of particles per cell is independent of the mesh cell size. So no adjustment is necessary.
If MPPKR (mass per particles through number of particles per kernel radius) is chosen, the size of particles is adjusted to get a constant number of particles within an sphKernelRadius. This ensures a reasonable amount of particles for the gradient computation.
If MPPDIR (mass per particle set directly) is chosen, the number of particles per cell depends on the release snow mass within a cell. The number of particles is computed using the cell area and the release thickness. To ensure a reasonable amount of particles for decreased mesh size and sphKernelRadius, the massPerParticle value should be decreased accordingly. This ensures a reasonable amount of particles for the gradient computation.
Regarding DEM cell sizes: - if a cell size XX different than the default 5 meters is chosen - and the provided DEM in Inputs is of different mesh cell size than XX - the folder DEMremeshed will be checked for a matching DEM. - if no matching DEM is found -> remeshing takes place
Using the default settings, the subdirectory ‘DEMremeshed’ is cleaned when starting simulations, to ensure remeshing. This can be changed in the configuration file (further details are provided in DEM input data).