[CIG-MC] Questions about CitcomS input parameters

[ELISA FIERRO]

Hi All,
I'm an italian PhD student in Geodynamics and the topic of my PhD is
modelling the rifting and rift to drift transition phase of the Red Sea by
CitcomS 3.3.1. I'm new of this software (and of the geodynamic modelling in
general) so I'm writing to you because I'm reading the manual but I'm not
able to understand the meaning of a lot of input parameters and I would
need a help.

I'm sorry in advance for the large number of the questions!!!!



   - side_sbcs=off/on  Do I have to set it on for a mantle convection
   modelling? and after having set it on, do I need to set or change other
   conditions related to it?



   - the* mgunit* parameters gathered in the mesh grid information (*mgunitx,
   mgunity, mgunitz *and* levels*). What are they for?


   - I'm not able to understand how I have to set the *lith_age_files*
(*lith.dat).
   *I know that the format of these files has to be *'n age'*, but *n *is
   for node? and if so, do I have to set an age for every node of the initial
   input mesh (like for the vx and vy inside the bvel.dat)?


   - When lith_age parameter is on I have to add the followed additional
   parameters for temperature boundary conditions:

              temperature_bound_adj=off
              depth_bound_adj=0.157
              width_bound_adj=0.08727
              lith_age_depth=0.0314

           What is their meaning? When do I have to set the
temperature_bound_adj off and on? Are the parameters depth_bound_adj and
width_bound_adj
           dimensionless like lith_age_depth? and if so, which equations do
I have to use to give them a dimension?

   - A lot of Momentum Equation Solver Parameters:

              node_assemble=on
              mg_cycle=1
              down_heavy=3
              up_heavy=3
              vlowstep=1000
              vhighstep=3
              max_mg_cycles=50
              uzawa=cg
              compress_iter_maxstep=100
              precond=on
              aug_lagr=on
              aug_number=2.0e3

            I didn't understand their meaning on the manual; What are V
cycle and W cycle?; What is the downward/upward smoothing?; what is the
preconditer? what is
            the meaning of the abbreviations *cg* and *bicg* related to the
uzawa algorithm?


   - Energy Equation Solver Parameters

              fixed_timestep=0.0         If it is equal to 0, the time step
is variable and it is determined dynamically. What does it mean?

              finetunedt=0.9                What is this parameter for? I
didn't understand the explanation on the manual

              filter_temp=off/on           I didn't understand what the
overshoots and undershoots of the temperature field are

              monitor_max_T=on/off    I didn't understand when I have to
set it on/off. The manual says that if it set on the maximum value of the
current and previous
                                                   temperature fields are
compared but I don't understand the meaning of this sentence.

              inputdiffusivity=1            diffusivity is for thermal
diffusivity? In my case will do I have to change this parameter since my
problem is integrated backward in
                                                   time? and how can I do
it?

   -  Dimensional information

             density=3340
             density_above=1030.0
             density_below=6600.0
             thermexp=3.0e-5
             refvisc=1.0e+21

            What do these parameters refer to exactly?


THANKS A LOT!!!

Elisa Fierro
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