.. _flow_cond_td_sec:

FLOW_CONDITION for time-dependent pressure, temperature and saturation
=============================================================================

FLOW_CONDITION can be used to assign a set of time-dependent pressure, temperature
and saturations constant in space. Such a flow condition, can be applied to the reservoir
with BOUNDARY_CONDITION to emulate a transient well or boundary conditions. ::

  FLOW_CONDITION <flow_condition_name>
    TYPE
      OIL_PRESSURE dirichlet
      OIL_SATURATION dirichlet
      GAS_SATURATION dirichlet
      BUBBLE_POINT dirichlet
      SOLVENT_SATURATION dirichlet
      TEMPERATURE dirichlet
    /
    OIL_PRESSURE <oil_pressure_data>
    OIL_SATURATION <oil_saturation_data>
    GAS_SATURATION <gas_saturation_data>
    BUBBLE_POINT <bubble_point_data>
    SOLVENT_SATURATION <solvent_saturation_data>
    TEMPERATURE <temp_data>
    INTERPOLATION <interpolation_type>
  /

where:

* <flow_condition_name>: name to be used in the :ref:`BOUNDARY_CONDITION<bc_ref_sec>` coupler blocks, to associate the flow condition with a surface region.
* <oil_pressure_data>: specify the pressure values for the whole region or at the datum. This can be either be a constant value or a list in case of a time-dependent data (see :ref:`transient data block<transient_data_block_sec>`)
* <oil_saturation_data>: specify the oil saturation values for the whole region. This can be either a constant value or a list in case of time-dependent data (see :ref:`transient data block<transient_data_block_sec>`).
* <gas_saturation_data>: specify the gas saturation values for the whole region. This can be either a constant value or a list in case of time-dependent data (see :ref:`transient data block<transient_data_block_sec>`).
* <bubble_point_data>: specify the bubble point values for the whole region. This can be either a constant value or a list in case of time-dependent data (see :ref:`transient data block<transient_data_block_sec>`).
* <temp_data> specify the temperature values for the whole region. This can be either a constant value or a list in case of time-dependent data (see :ref:`transient data block<transient_data_block_sec>`)
* <interpolation_type>: specifies the type of interpolation when a time-series for transient data are specified. It can be either “step” (the default), or “linear”. See :ref:`transient data block<transient_data_block_sec>` for mode details.


.. _transient_data_block_sec:

Transient data block to define time-dependent values within a flow condition
----------------------------------------------------------------------------------

When the value to be associated with a variable (e.g. pressure, saturation, temperature) is
time dependent, a time-series must be specified to define variable changes with time. This
can be done directly in the in input deck using the ``LIST`` sub-block, when the data to be
provided in the input deck is not too large. For a time series requiring n entries, ``LIST`` can be
used as follows: ::

  <VAR_NAME> LIST
    TIME_UNITS <time_units>
    DATA_UNITS <var_data_units>
    <t_1> <var_value_t_1>
    .....................
    <t_i> <var_value_t_i>
    ......................
    <t_n> <var_value_t_n>
  END

During the simulation, the value of the variable at time t is updated using the value
specified at the previous time if ``INTERPOLATION``, in :ref:`FLOW_CONDITION<flow_cond_sec>` is set to “step”, i.e.:

.. math::
  \mbox{for } t_i < t < t_{(i+1)} => \mbox{var_t} = \mbox{var_value_t_i}

Or with a linear interpolation between the two values corresponding to t_i and t_(i+1), if
INTERPOLATION is set to “linear”.

See example below: ::

  FLOW_CONDITION source
    TYPE
      RATE mass_rate
      TEMPERATURE dirichlet
    END
    RATE LIST
      TIME_UNITS d
      DATA_UNITS kg/s
      0.     1.0   0.0
      10.    1.0   0.0
      10.001 0.    0.0
      1d22   0.0   0.0
    /
    TEMPERATURE 80.0 C
  END

In the example above, ``RATE LIST`` is used to impose a transient rate. ``TIME_UNITS`` and
``DATA_UNITS`` specify the units of the data entered. Each transient rate entry, under ``RATE LIST`` specifies: the time for which the rate entries are given, the water rate, the oil rate, the
energy rate. In this specific case, the water rate is equal to 1.0 kg/s between 0 and 10 days, it then changes to 0 for the remainder of the simulation.

When the amount of data required to describe the time series becomes too large, this can
be provided by an external file, using a ``FILE`` keyword followed by the file name, as described in the example below: ::

  FLOW_CONDITION source
    TYPE
      RATE mass_rate
      TEMPERATURE dirichlet
    END
    RATE FILE injection_rate.dat
    TEMPERATURE 80.0 C
  END

where the file injection_rate.dat contains the time series, with the same format used by ``LIST``, see example below: ::

  DATA_UNITS kg/s
  0.   0.3 0.0
  1.   0.5 0.0
  2.   0.8 0.0
  3.   1.0 0.0
  4.   1.1 0.0
  5.   1.2 0.0
  6.   0.0 0.0
  1d22 0.0 0.0