.. _Chap:InputsInitialization:

Initialization
==============

The following inputs must be preceded by ``mfix`` and determine how we initialize a calculation:

+----------------------+-----------------------------------------------------------------------+-------------+--------------+
|                      | Description                                                           |   Type      | Default      |
+======================+=======================================================================+=============+==============+
| do_initial_proj      | Perform an initial projection                                         |    Bool     |  True        |
+----------------------+-----------------------------------------------------------------------+-------------+--------------+
| initial_iterations   | Number of pressure iterations to execute before time-marching         |  Int        |    3         |
+----------------------+-----------------------------------------------------------------------+-------------+--------------+
| scale_init_dt        | Factor by which ``dt`` is scaled in the initial iterations and step.  |    Real     |  1.0         |
|                      | Must be a value <= 1.0                                                |             |              |
+----------------------+-----------------------------------------------------------------------+-------------+--------------+

.. note::
   ``scale_init_dt`` is applied *before* ``dt_max`` when using adaptive time
   steps, i.e. the timestep is computed as ``min(max_dt, scale_init_dt * dt0)``
   where ``dt0`` is the step before scaling and bracketing, *not*
   ``scale_init_dt * min(max_dt, dt0)``. As a result, if ``max_dt`` is already
   smaller than the allowed adaptive timestep, changing ``scale_init_dt`` will
   have no effect.


+----------------------+-----------------------------------------------------------------------+-------------+--------------+
|                      | Description                                                           |   Type      | Default      |
+======================+=======================================================================+=============+==============+
| restart              | If set, then restart from this file rather than from scratch          |  String     |   None       |
+----------------------+-----------------------------------------------------------------------+-------------+--------------+



+----------------------+-----------------------------------------------------------------------+-------------+--------------+
|                      | Description                                                           |   Type      | Default      |
+======================+=======================================================================+=============+==============+
| repl_x               | Replicate initial data by this factor in the x-direction              |   Int       |    1         |
+----------------------+-----------------------------------------------------------------------+-------------+--------------+
| repl_y               | Replicate initial data by this factor in the y-direction              |   Int       |    1         |
+----------------------+-----------------------------------------------------------------------+-------------+--------------+
| repl_z               | Replicate initial data by this factor in the z-direction              |   Int       |    1         |
+----------------------+-----------------------------------------------------------------------+-------------+--------------+
