.. index:: connections preprocessing
.. _connections_preprocessing:
Preprocessing
-------------
Right before the actual run is solved, the model the user uploaded is
preprocessed (cf. :numref:`model_initflow`). This has a particular meaning for connections and can be
described by two different phases:
1. Initialisation of the ``*_i_to_j`` columns.
2. Symmetrization of the ``*_j_to_i`` columns.
.. index:: initialisation
Step 1: Initialisation
""""""""""""""""""""""
:term:`Initialisation <initialisation>` deals with the ``*_i_to_j`` columns.
**This phase does not directly affect the** ``*_j_to_i`` **ones**.
For each row of the model, any **empty or blank** cell within the ``*_i_to_j``
columns will be set to ``0.0``.
.. index:: symmetrization
Step 2: Symmetrization
""""""""""""""""""""""
:term:`Symmetrization <symmetrization>` deals with the ``*_j_to_i`` columns. **This phase never
affects the** ``*_i_to_j`` **ones**.
This "symmetrisation" process means that connections are assumed
symmetric by default.
The user shall fill the ``*_i_to_j`` columns. ``*_j_to_i`` is not
mandatory. The empty ``*_j_to_i`` columns will be automatically copied
from ``*_i_to_j``.
A connection may be partially symmetric. For example, a connection may
have the same discharge coefficient (`cp`) for both ways, but different
venting area. In this case, only the asymmetric values need to be
filled.
.. _connections_examples:
Common examples
---------------
The following examples show the most common connections and propose the
best way to idealize them.
.. index::
double: decompression feature; passive venting (symmetric)
Passive vent
""""""""""""
Passive vents are the most simple connections. Passive vents are always
symmetrical (although you may define unsymmetrical venting area).
.. _passive_vent:
.. figure:: fig/sketch_passive_vent.png
:width: 400pt
:align: center
:alt: Create a project
:figclass: align-center
:class: screenshot
Passive vent (defined as a grid) between volumes 2 and 7
Example: A connection (ID19) is a passive vent (symmetric) between volumes
2 and 7. The total vent area is 0.3m^2, with a discharge coefficients of 0.4.
Such a feature is shown at :numref:`passive_vent`.
The ESonix pre-process phase would prepare the full connection as described
below (in bold the default values determined by ESonix). Pay attention to the
*symmetrization* process to fill the ``_j_to_i`` columns.
.. table:: Passive vent parameters Example
+-----------------------------+------------+----------------------------------------+--------------+
| Column | User input | Preprocess | Actual input |
+=============================+============+========================================+==============+
| ``id`` | 19 | .. | *19* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_i`` | 2 | .. | *2* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_j`` | 7 | .. | *7* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``door`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_latency`` | .. | Default to zero | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_i_to_j`` | 0.3 | .. | *0.3* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_i_to_j`` | 0.4 | .. | *0.4* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_j_to_i`` | .. | Default to ``vent_area_i_to_j`` | **0.3** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_j_to_i`` | .. | Default to ``opening_pressure_i_to_j`` | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_j_to_i`` | .. | Default to ``opening_time_i_to_j`` | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_j_to_i`` | .. | Default to ``cp_i_to_j`` | **0.4** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``comments`` | .. | Default to null string | **""** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``ovar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``exvar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
.. index::
double: decompression feature; decompression panel (symmetric)
Standard decompression panel (Bi-directionnel)
""""""""""""""""""""""""""""""""""""""""""""""
Decompression panels are activated once the delta pressure pushing on it reach a target value.
It is most of the time *fully symmetric*: the same delta pressure threshold
triggers the mechanism and the same vent area is cleared.
.. _simple_decomp_panel:
.. figure:: fig/sketch_decomp_panel_01.png
:width: 400pt
:align: center
:alt: Create a project
:figclass: align-center
:class: screenshot
Standard Decompression panel between volumes 2 and 7 (designed with
ball-catch for this particular example)
Example: A decompression panel defines the connection ID19. The total released area is 0.5m^2. The panel opens
for a pressure of 1.5bar, and is assumed to open instantaneously (``opening_time`` = 0).
Such a feature is shown at :numref:`simple_decomp_panel`.
The ESonix pre-process phase would prepare the full connection as described
below (in bold the default values determined by ESonix). Pay attention to the
*symmetrization* process to fill the ``_j_to_i`` columns.
.. table:: Standard decompression panel parameters Example
+-----------------------------+------------+----------------------------------------+--------------+
| Column | User input | Preprocess | Actual input |
+=============================+============+========================================+==============+
| ``id`` | 19 | .. | *19* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_i`` | 2 | .. | *2* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_j`` | 7 | .. | *7* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``door`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_latency`` | .. | Default to zero | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_i_to_j`` | 0.3 | .. | *0.3* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_i_to_j`` | 1.5 | .. | *1.5* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_i_to_j`` | 0.6 | .. | *0.6* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_j_to_i`` | .. | Default to ``vent_area_i_to_j`` | **0.3** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_j_to_i`` | .. | Default to ``opening_pressure_i_to_j`` | **1.5** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_j_to_i`` | .. | Default to ``opening_time_i_to_j`` | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_j_to_i`` | .. | Default to ``cp_i_to_j`` | **0.6** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``comments`` | .. | Default to null string | **""** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``ovar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``exvar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
.. index::
double: decompression feature; decompression panel (non-symmetric)
Unidirectional decompression panel
""""""""""""""""""""""""""""""""""
Unidirectional decompression panels are activated only for one direction
.. _blind_decomp_panel:
.. figure:: fig/sketch_decomp_panel_02.png
:width: 400pt
:align: center
:alt: Create a project
:figclass: align-center
:class: screenshot
Unidirectional decompression panel between volumes 2 and 7
Example: Same example as above, but the panel can only open from 7 to 2.
Such a feature is shown at :numref:`blind_decomp_panel`.
One way to achieve this is to reduce ``vent_area_i_to_j`` to 0 (no vent area
from 2 to 7), and to set ``vent_area_j_to_i`` to 0.3.
.. table:: Unidirectional decompression panel parameters Example
+-----------------------------+------------+----------------------------------------+--------------+
| Column | User input | Preprocess | Actual input |
+=============================+============+========================================+==============+
| ``id`` | 19 | .. | *19* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_i`` | 2 | .. | *2* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_j`` | 7 | .. | *7* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``door`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_latency`` | .. | Default to zero | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_i_to_j`` | 0.6 | .. | **0.6** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_j_to_i`` | 0.3 | | *0.3* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_j_to_i`` | 1.5 | .. | **1.5** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_j_to_i`` | .. | Default to ``opening_time_i_to_j`` | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_j_to_i`` | 0.6 | | **0.6** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``comments`` | .. | Default to null string | **""** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``ovar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``exvar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
.. warning:: once the panel is open the air can freely flow in both direction. If the differential pressure inverts the air flow from "i_to_j" will be based on the actual calculated opened area with the discharge coefficient "cp_i_to_j". Therefore this discharge coefficient should be always specified.
.. note:: another way of achieving a unidirectional decompression panel opening would be to set an artificially high opening pressure in the opposite direction.
.. index::
double: decompression feature; decompression panel (non-symmetric)
Nested differential decompression panel
""""""""""""""""""""""""""""""""""""""""
This particular design is sometimes useful to optimize a decompression layout.
.. _nested_panel:
.. figure:: fig/sketch_decomp_panel_03.png
:width: 400pt
:align: center
:alt: Create a project
:figclass: align-center
:class: screenshot
Nested differential Decompression panel between volumes 2 and 7
Example. As shown in :numref:`nested_panel`, a decompression feature (let say
with ID 23) can open in both directions with the same triggering pressure, but
with different area. This would be achieved this way:
.. table:: Nested decompression panel parameters Example
+-----------------------------+------------+----------------------------------------+--------------+
| Column | User input | Preprocess | Actual input |
+=============================+============+========================================+==============+
| ``id`` | 23 | .. | *23* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_i`` | 2 | .. | *2* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_j`` | 7 | .. | *7* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``door`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_latency`` | .. | Default to zero | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_i_to_j`` | 0.3 | .. | *0.3* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_i_to_j`` | 1.5 | .. | *1.5* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_i_to_j`` | 0.6 | .. | *0.6* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_j_to_i`` | 0.8 | | *0.8* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_j_to_i`` | .. | Default to ``opening_pressure_i_to_j`` | **1.5** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_j_to_i`` | .. | Default to ``opening_time_i_to_j`` | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_j_to_i`` | .. | Default to ``cp_i_to_j`` | **0.6** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``comments`` | .. | Default to null string | **""** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``ovar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``exvar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
.. index::
double: decompression feature; door (symmetric)
Simple non-decompressing door
"""""""""""""""""""""""""""""""""""""
A non-decompressing :term:`door` is considered as a *passive* vent when the *opened-doors* configuration
is ran. No more data except ``door`` and ``cp_i_to_j`` are required (beside
``id``, ``vol_j`` and ``vol_j``!)
.. _non_decompressing_door:
.. figure:: fig/sketch_simple_non_decomp_door.png
:width: 400pt
:align: center
:alt: Create a project
:figclass: align-center
:class: screenshot
Simple non-decompressing door between volumes 2 and 7
Example: A simple 2.2m² door (let say ID9) connects
compartments 2 and 7 (cf. :numref:`non_decompressing_door`).
Usually, such a big clean vent is assumed to have a
discharge coefficient of 0.8. When the decompression analysis is ran with the
*closed-doors* initial conditions, this venting is ignored (the door is closed
and will remain closed) whereas for the *opened-doors* initial conditions, the
full door is opened and will remain opened as a 2.2m² passive vent.
.. table:: Simple Non-decompressing door
+-----------------------------+------------+----------------------------------------+--------------+
| Column | User input | Preprocess | Actual input |
+=============================+============+========================================+==============+
| ``id`` | 9 | .. | *9* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_i`` | 2 | .. | *2* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_j`` | 7 | .. | *7* |
+-----------------------------+------------+----------------------------------------+--------------+
| ``door`` | 2.2 | | *2.20* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_latency`` | .. | Default to zero | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_i_to_j`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_i_to_j`` | 0.8 | .. | *0.8* |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_j_to_i`` | .. | | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_j_to_i`` | .. | Default to ``opening_pressure_i_to_j`` | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_j_to_i`` | .. | Default to ``opening_time_i_to_j`` | **0** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_j_to_i`` | .. | Default to ``cp_i_to_j`` | **0.8** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``comments`` | .. | Default to null string | **""** |
+-----------------------------+------------+----------------------------------------+--------------+
| ``ovar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``exvar`` | .. | Default to zero | **0** |
| | | | |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
.. index::
double: decompression feature; door (non-symmetric)
.. _simple_decompression_door_example:
Simple decompressing door
"""""""""""""""""""""""""""""
A decompressing :term:`door` is considered to clear its full frame area when the
:math:`\Delta_P` reach the triggering pressure. For an *opened-door* initial
condition run, the decompressing feature will not be active, since the door
itself is already opened.
This kind of decompression item is usually **not symmetric**: the static door frame allows the
door to rotate only in one direction.
.. _decompressing_door:
.. figure:: fig/sketch_simple_decomp_door.png
:width: 400pt
:align: center
:alt: Create a project
:figclass: align-center
:class: screenshot
Simple decompressing door between volumes 2 and 7
Example: The same example as above is used, except that the door is able
to open from 7 to 2 when :math:`\Delta_P` reaches 1.5bar. Additionnally, an
opening time of 0.3 seconds will be used. Will still need to set the discharge
coefficient for ``i_to_j`` since the door will be opened for the *opened-door*
initial conditions.
.. table:: Simple decompressing door
+-----------------------------+------------+----------------------------------------+--------------+
| Column | User input | Preprocess | Actual input |
+=============================+============+========================================+==============+
| ``id`` | 9 | .. | *9* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_i`` | 2 | .. | *2* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_j`` | 7 | .. | *7* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``door`` | 2.2 | | *2.20* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_latency`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_i_to_j`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_i_to_j`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_i_to_j`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_i_to_j`` | 0.8 | .. | *0.8* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_j_to_i`` | 2.2 | | *2.2* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_j_to_i`` | 1.5 | | *1.5* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_j_to_i`` | 0.3 | | *0.3* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_j_to_i`` | .. | Default to ``cp_i_to_j`` | **0.8** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``comments`` | .. | Default to null string | **""** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``ovar`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``exvar`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
Door nesting a decompression panel
""""""""""""""""""""""""""""""""""
Contrary to the example above (:ref:`simple_decompression_door_example`), the door has no
decompression mechanism, but hosts a nested decompression panel (cf.
:numref:`door_with_nested_panel`).
For illustration purposes, and to keep a certain level of complexity,
the nested panel is considered blind --opening only from volume 2 to volume 7--
which is not common.
The door itself will not be triggered with maximum Δp. However its 1.05m²
nested panel will, only from volume 2 to volume 7.
Values for ``i_to_j`` data has to be filled, and values for ``j_to_i`` as well,
but set to 0 to avoid :term:`symmetrization` (at least for the ``vent_area``),
as shown in :numref:`door_with_nested_panel_table`).
.. _door_with_nested_panel:
.. figure:: fig/sketch_door_with_panel.png
:width: 400pt
:align: center
:alt: Create a project
:figclass: align-center
:class: screenshot
Door nesting a decompression panel opening from 2 to 7
.. warning:: It is often a bad idea to define the panel as another item
(another row) as the door. Indeed, in the latter case,
during an opened-door load case, the panel will still be active and may
be triggered, adding a new vent area that shouldn't be!
.. _door_with_nested_panel_table:
.. table:: Door with nested decompression Panel
+-----------------------------+------------+----------------------------------------+--------------+
| Column | User input | Preprocess | Actual input |
+=============================+============+========================================+==============+
| ``id`` | 9 | .. | *9* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_i`` | 2 | .. | *2* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vol_j`` | 7 | .. | *7* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``door`` | 2.2 | | *2.20* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_latency`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_i_to_j`` | 1.05 | | *1.05* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_i_to_j`` | 1.5 | | *1.5* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_i_to_j`` | 0.3 | | *0.3* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_i_to_j`` | 0.8 | .. | *0.8* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``vent_area_j_to_i`` | 0 | | *0* |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_pressure_j_to_i`` | .. | Default to ``opening_pressure_i_to_j`` | **1.5** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``opening_time_j_to_i`` | .. | Default to ``opening_time_i_to_j`` | **0.3** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``cp_j_to_i`` | .. | Default to ``cp_i_to_j`` | **0.8** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``comments`` | .. | Default to null string | **""** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``ovar`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+
| ``exvar`` | .. | Default to zero | **0** |
| | | | |
+-----------------------------+------------+----------------------------------------+--------------+