Restarting with a new resolution

[ColumnarPhD]

Hi everyone, I have been getting to grips with Micress for the past few months, mostly successfully but hit an issue that seems to need some outside help.

I am running 2D simulations from the surface chill zone through the columnar region, my starting grains are very small so I need a relatively high resolution early on, but after competition has eliminated many I am trying to switch to a coarser resolution in order to complete the simulation in a reasonable timeframe.

The manual gave me the impression that restarting with the structure only command will allow me to take the microstructure in the _rest file and change anything else including the resolution. However when I do this the file restarts from the filler grain data in the input file that Micress requires but then supposedly disregards, completely ignoring the structure in the _rest file.

Here is the restart code

# Restart options
# ===============
# Restart using old results?
# Options: new restart [reset_time | structure_only]
restart structure_only
# How many restart files shall be read?
1
# For each restart file a grain number and (optionally) a
# shift in all dimensions (in grid cells) and a character for
# rotation options must be specified:
# grain number [shift X (int) shift Y (int) shift Z (int) rot(string)] ?
# Rotation options: "xz+90" "xz-90" "xz180" "xy+90" ... "yz180"
159
# Name of restart file?
Results_ResTest/150_Start
#
#
# Name of output files
# ====================
# Name of result files?
Results_ResTest2/150_Cont
# Overwrite files with the same name?
# Options: overwrite write_protected append
# [zipped|not_zipped|vtk]
# [unix|windows|non_native]
overwrite

Does anyone have any advice? Either correcting a mistake or a completely different approach.

[Bernd]

Dear ColumnarPhD,

Welcome to the MICRESS Forum!

I guess the problem why nothing happens is that there is no grain number 159 present in your initial microstructure. The idea of the "structure_only" option is that you can define a frame for the initial microstructure which you want to read from the .rest file. By this way, several microstructures can be read and combined in a new RVE by definition of the corresponding frames (see here).
You defined grain number 159 as frame for the structure from .rest. If it does not exist (according to your 'grain input' in the driving file) nothing happens. I guess that you want to read the .rest file and fill the whole domain, and your 'Grain Input' is empty. Then you should rather specify grain number 0 as frame which is present by default.

Nevertheless, I am not sure whether restart does really what you want. The new zoom functionality of MICRESS 6.4 allows for increasing resolution by a factor of 2 or 3, but this is the opposite of what you need.

Alternatively, you could read the initial microstructure "from file", which in this case would be the normal MICRESS output files .korn and .conc* which can be converted to VTK or ASCII format by use of DP_Micress (look here or here).

Bernd

[ColumnarPhD]

Hi Bernd,

Thanks for the insight, I had assumed that the grain number input was for some reason the number of grains that were in the file being read. But it sounds like both of those approaches should work so thanks for the help.