### 21.2.2. Working with Monitors

#### 21.2.2.1. Setting up Monitors

To add basic monitors:

1. Click Output Control or select Insert > Solver > Output Control from the main menu.

   The Output Control dialog box will appear.

2. Click the Monitor tab.

3. Select Monitor Objects.

4. Select which variables to monitor (Balances, Forces, Residuals, Totals, Particles).

   By default, all of the listed quantities are monitored.

To add monitors for points and expressions:

1. In the Monitor Points and Expressions frame, click Add new item .

   The Insert Monitor Point dialog box appears, asking for the name of a new monitor.

2. Enter a name, or accept the default name, and then click OK.

   The [Monitor Name] frame expands to show a set of input fields.

3. Specify the settings for the monitor object. For details, see Monitor Points And Expressions List Box.

4. Add more monitor objects as desired.

To add monitors for aerodynamic damping (for transient blade row runs that involve boundaries that move periodically):

1. In the Aerodynamic Damping frame, click Add new item .

   The Insert Aerodynamic Damping dialog box appears, asking for the name of a new monitor.

2. Enter a name, or accept the default name, and then click OK.

   The [Aerodynamic Damping] frame expands to show a set of input fields.

3. Specify the settings for the monitor object. For details, see Aerodynamic Damping: Frame Overview.

4. Add more monitor objects as desired.

Click OK or Apply to set the definitions of all of the monitor objects. All monitor points will be displayed in the viewer.

#### 21.2.2.2. Transient/ Mesh Deformation Runs

For a transient run or run with a moving mesh, the monitor point location can either update with the mesh or it can remain based off of the initial mesh. For details, see [Monitor Name]: Monitor Location Control.

#### 21.2.2.3. Output Information

Information on the variables to be monitored is given near the start of the .out file. In the following example the variables Velocity and Pressure were requested for the Output Variables List in the .ccl file.

    +-----------------------------------------------------------------------+
    |                       User Defined Monitor Points                     |
    +-----------------------------------------------------------------------+
    Monitor Point: my monitor point
    Domain: rotor
    Monitor vertex location (x,y,z):     4.101E-01,  5.703E-02,  5.263E-02
    User specified location (x,y,z):     4.100E-01,  5.618E-02,  4.951E-02
    Distance to user specified location:                         3.231E-03
    Valid variables from output variable list:
                   Air Ideal Gas.Velocity u
                   Air Ideal Gas.Velocity v
                   Air Ideal Gas.Velocity w
                   Pressure
    +-----------------------------------------------------------------------+

The “Monitor vertex location” shows the actual location that is being monitored (the closest vertex to the “User specified location”). The “Distance to user specified location” shows the difference between the specified and actual monitoring location.

The “Output variable list” shows the full name of all variables that will be monitored.

#### 21.2.2.4. Expression

When using the `Expression` option for a monitor, the results of the evaluated expression are output at each iteration. Enter an expression that evaluates to a single value at each timestep. The following are examples of expressions that could be monitored:

- `force()@MainWall / (0.5*areaAve(density)@Inlet * areaAve(vel)@Inlet * area()@MainWall)`

- `volumeAve(CO2.mf)@Domain 1`

The variable names should be preceded with the fluid name when applicable. You can view a list of variable names in the Expression details view by right-clicking in the Definition window when editing an expression.

#### 21.2.2.5. Viewing Monitor Values during a Run

You can view a plot of monitor point values during a solver run. For details, see Monitors Tab in the CFX-Solver Manager User's Guide.

#### 21.2.2.6. Viewing Monitor Point Values after a Run

You can view monitor point values easily in the CFX-Solver Manager after a run. For details, see Exporting Plot Variables and Coordinates in the CFX-Solver Manager User's Guide.

You can also extract monitor point values from a .res file using the `cfx5dfile` command. The following syntax is used:

    cfx5dfile <file> -read-monitor

where `<file>` is a CFX-Solver input or results file containing monitor point information. The output is sent to standard output (you may want to add a redirect to write the output to a text file, for example:

    cfx5dfile <file> -read-monitor > out.txt

The output is produced as a list of variable names, followed by a comma-delimited list of values that correspond to the order of variable names. One line of these values is produced for every iteration that has been carried out.

You can enter:

    cfx5dfile -help

to obtain more information.

#### 21.2.2.7. Using Monitors in CEL

Within CEL expressions, you can use the `probe` function to refer to monitors and monitor statistics. For example:

- If `Monitor Point 1` is an expression-based monitor (a monitor point with Option set to `Expression`), with `Standard Deviation` in the specified statistics list:

  - You can obtain the value of (the expression being monitored by) `Monitor Point 1` at the current time step with:

    `probe(Expression Value)@Monitor Point 1`

    (Here, “`Expression Value`” is not an example; it is part of the syntax.)

  - You can obtain the standard deviation of the value of `Monitor Point 1` over the current interval (the size of which is specified in the definition of `Monitor Point 1`) with:

    `probe(Expression Value.Standard Deviation)@Monitor Point 1`

- If `Monitor Point 2` is a location-based monitor (a monitor with Option set to `Cartesian Coordinates` or `Cylindrical Coordinates`):

  - You can obtain the value of variable `Pressure` at `Monitor Point 2` at the current time step with:

    `probe(Pressure)@Monitor Point 2`

Note: You cannot directly obtain statistics from a location-based monitor. As a workaround, you can obtain statistics from an expression-based monitor, with the expression including a probe of a variable at the location-based monitor.

Note: The `probe` function does not calculate a value for a statistic until the defined interval is complete. As a result, a “probe” function that retrieves a statistic from an expression-based monitor:

- Should not be used in a CEL expression for a quantity that is required at all times, for example, a boundary condition.

- Causes any interrupt control condition in which it is used to be invalid (and ignored) until the required interval is complete.

For details on setting up monitor statistics, see [Monitor Name]: Monitor Statistics.

For an example of using a monitor statistic as part of interrupt control, see Using Interrupt Control in Cases with Transient Convergence Behavior in the CFX-Solver Modeling Guide.

Release 18.2 - © ANSYS, Inc. All rights reserved.