I am using Coreform Cubit version: 2023.4 on Ubuntu 22.04 LTS.
I have a mesh with x and y coordinates in latitude and longitude degrees and depth in km. I want to create a brick element, mesh it, and export the coordinates in the same input format.
Hi,
Cubit is dimensionless by default. If you use a consistent set of dimensions for all values, you will create a valid mesh in that space. All materials units in the analysis code must also be in the same set of units. That means that if you specify the model size in kilometers you would also have to adjust your materials and loads to match.
The pylith (Geodynamics - Resources: PyLith: About) examples use the Algebraic Preprocessor (APREPRO) units function to be explicit about the units. All APREPRO variables must be surrounded in braces.
Here is a simplified version of the box-3d example from pylith that uses units.
# Set units to SI.
# ----------------------------------------------------------------------
${Units('si')}
# ----------------------------------------------------------------------
# Reset geometry.
# ----------------------------------------------------------------------
reset
# ----------------------------------------------------------------------
# Create block
# ----------------------------------------------------------------------
# Block is 12km x 12km x 9km
# -6 km <= x <= 6 km
# -6 km <= y <= 6 km
# -9 km <= z <= 0 km
brick x {12.0*km} y {12.0*km} z {9.0*km}
# Center of block will be at (0,0,0), so move it down half the height
# to align the top at z=0.
volume 1 move x 0 y 0 z {-4.5*km}
This allows you to specify the units in kilometers in the journal file and it converts the values to standard SI meter units. The actual size of the box in Cubit is 12 000 by 12 000 by 9 000. You would use SI units for material properties and loads in your analysis code.
Is this helpful?
Karl