You are here: Physics Modules > Cavitation > Output Variables

5.4.4 Output Variables

This section explains the outputs available in the Cavitation module. They are categorized as follows:

• Primary Variables
• Property Variables
• Derived Variables
• Integrated Quantities
• Avg/Max Vapor Volume Fraction Distribution
• Avg/Max Gas Volume Fraction Distribution
• Avg/Max Vapor Rate Distribution
• Avg/Max Gas Rate Distribution
• Avg/Max Vapor Damage Power Distribution
• Avg/Max Gas Damage Power Distribution
• Gas Volume Fraction Distribution
• Gas Damage Power Distribution

 

Note: In order to display the contours and X-Y plots, or to write the outputs into an ascii file, the outputs on each Geometric entity (such as Boundary, Volume, Interface or Points) need to be activated in the Model Tab of the Properties Panel.

 

Primary Variables

Primary Variables are the fundamental variables that characterize the physical process in the module. They are usually obtained by directly solving transport equations or through physical constitutions. The primary variables can be displayed in the GUI Viewing Window for selected Geometric Entities as well as written to the ascii file Filename_points.txt. They can also be viewed as X-Y Plots for Point Probes.

For the Cavitation module, a list of Primary Variables is shown in the table below:

Cavitation Module Primary Variables
Label in Results Panel Variables List	Label in GUI X-Y Plot Menu	Label in points.txt	Definition	Units	Display/Output Options	Relevant Cavitation Models
Gas Mass Fraction	Gas Mass Fraction	Fgas_	NCG mass fraction (over fluid mass)	-	At a Point and in the GUI Display Window	All
Vapor Mass Fraction	Vapor Mass Fraction	Fvap_	Vapor mass fraction (over fluid mass)	-	At a Point and in the GUI Display Window	All
Dissolved Gas Mass Fraction	Dissolved Gas Mass Fraction	Dgas_	Dissolved NCG mass fraction (over fluid mass)	-	At a Point and in the GUI Display Window	Equilibrium Dissolved Gas, Dissolved Gas, Full Gas

Table 5.22 - Cavitation module primary variables

Primary Variables are automatically activated for output on selected Geometric Entities, including Boundaries, Derived Surfaces, Interfaces, Streamline, Particles and/or Volumes, depending on the modules selected.

 

Property Variables

Property Variables are the physical properties for the fluid(s) and solid(s) in the domain. They are required as a part of the solution. They may be displayed in the GUI Viewing Window for selected Geometric Entities as well as written to the ascii file Filename_points.txt (when activated). They can also be viewed as X-Y Plots for Point Probes.

For the Cavitation module, a list of Property Variables is shown in the table below:

As shown in Figure 5.78, Property Variables are automatically activated for output on selected Geometric Entities, including Boundaries, Derived Surfaces, Interfaces, Streamline, Particles and/or Volumes, depending on the modules selected. For Point Probes, however, explicit activation is required.

 

 

 

 

Figure 5.78 - Output activation for points-Property variables

 

Derived Variables

Derived Variables are engineering data computed from the Primary Variables. While not required as a part of the solution, they provide valuable information for analysis of the results. They can be displayed in the GUI Viewing Window for selected Geometric Entities as well as written to the ascii file Filename_points.txt (when activated). They can also be viewed as X-Y Plots for Point Probes.

A list of the Derived Variables for the Cavitation module is shown below:

As shown in Figure 5.79, Derived Variables are automatically activated for output on selected Geometric Entities, including Boundaries, Derived Surfaces, Interfaces and/or Volumes, depending on the modules selected. For Point Probes, however, explicit activation is required.

 

 

 

 

Figure 5.79 - Output activation for points-Derived variables

 

Integrated Quantities

An Integrated Output is the averaged or total value of a variable over a Boundary, Interface or Volume. When available and activated, the integrated quantities can be stored in the ascii file Filename_integrals.txt as well as be displayed in the GUI using X-Y Plots.

To access the variables listed below using expressions, the syntax given under Expressions column in Table 5.25 is used with a suffix “@boundary or volume name” such as allgasvol_pipe = cavitation.gas.v_t@pipe.

A table of the Integrated Quantities for the Cavitation module is shown below:

For a selected Geometric entity, the integrated outputs must be explicitly activated as shown in Figure 5.80.

 

 

 

 

Figure 5.80 - Output activation-Integrated quantities

 

Avg/Max Vapor Volume Fraction Distribution

The Avg/Max Vapor Volume Fraction Distribution outputs are spatial distributions of "Time Average" or "Time Maximum" values of vapor volume fraction in boundaries:

• "Time Average" is the average values during a "Period" of time.
• "Time Maximum" is the maximum values encountered during a "Period" of time.

The "Period" is defined as number of time steps of a transient simulation. This “Period” is specified by the Cycle Computation Interval. The Avg/Max Vapor Volume Fraction Distribution output is activated for a selected boundary as follows:

• Click Common in the Model Panel.
• In Properties Panel > Model Tab, set Cycle Computation Interval, which is the number of time steps for the "Period" user wants to calculate time average, or find minimum and maximum values.
• Select Geometric Entities Panel > Boundaries > [Desired Boundary]
• Select Properties Panel > Model Tab > Cavitation > Output > User Select > Avg/Max Vapor Volume Fraction Distribution > Yes

The added outputs are shown in the Results Panel under Variable > Boundary Variables as shown in Figure 5.82. They are plotted as contours on the selected boundary.

Figure 5.81 - Avg/Max Vapor Volume Fraction Distribution BC

Figure 5.82 - Results Display

The Average and Maximum Vapor Volume Fraction Distributions on the boundary are stored in the files: Filename_boundary_ average_vapor_volume_fraction.txt and Filename_boundary_ max_vapor_volume_fraction.txt respectively. They are written at the same frequency as the result files are saved.

 

Avg/Max Gas Volume Fraction Distribution

The Avg/Max Gas Volume Fraction Distribution outputs are spatial distributions of "Time Average" or "Time Maximum" values of gas volume fraction in boundaries:

• "Time Average" is the average values during a "Period" of time.
• "Time Maximum" is the maximum values encountered during a "Period" of time.

The "Period" is defined as number of time steps of a transient simulation. This “Period” is specified by the Cycle Computation Interval. The Avg/Max Gas Volume Fraction Distribution output is activated for a selected boundary as follows:

• Click Common in the Model Panel.
• In Properties Panel > Model Tab, set Cycle Computation Interval, which is the number of time steps for the "Period" user wants to calculate time average, or find minimum and maximum values.
• Select Geometric Entities Panel > Boundaries > [Desired Boundary]
• Select Properties Panel > Model Tab > Cavitation > Output > User Select > Avg/Max Gas Volume Fraction Distribution > Yes

The added outputs are shown in the Results Panel under Variable > Boundary Variables as shown in Figure 5.84. They are plotted as contours on the selected boundary.

 

Figure 5.83 - Avg/Max Gas Volume Fraction Distribution BC

Figure 5.84 - Results Display

The Average and Maximum Gas Volume Fraction Distributions on the boundary are stored in the files: Filename_boundary_ average_gas_volume_fraction.txt and Filename_boundary_ max_gas_volume_fraction.txt respectively. They are written at the same frequency as the result files are saved.

 

Avg/Max Vapor Rate Distribution

The Avg/Max Vapor rate Distribution outputs are spatial distributions of "Time Average" or "Time Maximum" values of vapor volume rate in boundaries:

• "Time Average" is the average values during a "Period" of time.
• "Time Maximum" is the maximum values encountered during a "Period" of time.

The "Period" is defined as number of time steps of a transient simulation. This “Period” is specified by the Cycle Computation Interval. The Avg/Max Vapor rate Distribution output is activated for a selected boundary as follows:

• Click Common in the Model Panel.
• In Properties Panel > Model Tab, set Cycle Computation Interval, which is the number of time steps for the "Period" user wants to calculate time average, or find minimum and maximum values.
• Select Geometric Entities Panel > Boundaries > [Desired Boundary]
• Select Properties Panel > Model Tab > Cavitation > Output > User Select > Avg/Max Vapor rate Distribution > Yes

The added outputs are shown in the Results Panel under Variable > Boundary Variables as shown in Figure 5.86. They are plotted as contours on the selected boundary.

 

Figure 5.85 - Avg/Max Vapor rate Distribution BC

Figure 5.86 - Results Display

The Average and Maximum Vapor Volume rate Distributions on the boundary are stored in the files: Filename_boundary_ average_vapor_volume_rate.txt and Filename_boundary_ max_vapor_volume_rate.txt respectively. They are written at the same frequency as the result files are saved.

 

Avg/Max Gas Rate Distribution

The Avg/Max Gas rate Distribution outputs are spatial distributions of "Time Average" or "Time Maximum" values of gas volume rate in boundaries:

• "Time Average" is the average values during a "Period" of time.
• "Time Maximum" is the maximum values encountered during a "Period" of time.

The "Period" is defined as number of time steps of a transient simulation. This “Period” is specified by the Cycle Computation Interval. The Avg/Max Gas rate Distribution output is activated for a selected boundary as follows:

• Click Common in the Model Panel.
• In Properties Panel > Model Tab, set Cycle Computation Interval, which is the number of time steps for the "Period" user wants to calculate time average, or find minimum and maximum values.
• Select Geometric Entities Panel > Boundaries > [Desired Boundary]
• Select Properties Panel > Model Tab > Cavitation > Output > User Select > Avg/Max Gas rate Distribution > Yes

The added outputs are shown in the Results Panel under Variable > Boundary Variables as shown in Figure 5.88. They are plotted as contours on the selected boundary.

 

Figure 5.87 - Avg/Max Gas rate Distribution BC

Figure 5.88 - Results Display

The Average and Maximum Gas Volume rate Distributions on the boundary are stored in the files: Filename_boundary_ average_gas_volume_rate.txt and Filename_boundary_ max_gas_volume_rate.txt respectively. They are written at the same frequency as the result files are saved.

 

Avg/Max Vapor Damage Power Distribution

The Avg/Max Vapor Damage Power Distribution outputs are spatial distributions of "Time Average" or "Time Maximum" values of Vapor damage power in boundaries:

• "Time Average" is the average values during a "Period" of time.
• "Time Maximum" is the maximum values encountered during a "Period" of time.

The "Period" is defined as number of time steps of a transient simulation. This “Period” is specified by the Cycle Computation Interval. The Avg/Max Vapor Damage Power Distribution output is activated for a selected boundary as follows:

• Click Common in the Model Panel.
• In Properties Panel > Model Tab, set Cycle Computation Interval, which is the number of time steps for the "Period" user wants to calculate time average, or find minimum and maximum values.
• Select Geometric Entities Panel > Boundaries > [Desired Boundary]
• Select Properties Panel > Model Tab > Cavitation > Output > User Select > Avg/Max Vapor Damage Power Distribution > Yes

The added outputs are shown in the Results Panel under Variable > Boundary Variables as shown in Figure 5.90. They are plotted as contours on the selected boundary.

 

Figure 5.89 - Avg/Max Vapor Damage Power Distribution BC

Figure 5.90 - Results Display

The Average and Maximum Vapor Damage power Distributions on the boundary are stored in the files: Filename_boundary_ average_vapor_damage_power.txt and Filename_boundary_ max_vapor_damage_power.txt respectively. They are written at the same frequency as the result files are saved.

 

Avg/Max Gas Damage Power Distribution

The Avg/Max Gas Damage Power Distribution outputs are spatial distributions of "Time Average" or "Time Maximum" values of Gas damage power in boundaries:

• "Time Average" is the average values during a "Period" of time.
• "Time Maximum" is the maximum values encountered during a "Period" of time.

The "Period" is defined as number of time steps of a transient simulation. This “Period” is specified by the Cycle Computation Interval. The Avg/Max Gas Damage Power Distribution output is activated for a selected boundary as follows:

• Click Common in the Model Panel.
• In Properties Panel > Model Tab, set Cycle Computation Interval, which is the number of time steps for the "Period" user wants to calculate time average, or find minimum and maximum values.
• Select Geometric Entities Panel > Boundaries > [Desired Boundary]
• Select Properties Panel > Model Tab > Cavitation > Output > User Select > Avg/Max Gas Damage Power Distribution > Yes

The added outputs are shown in the Results Panel under Variable > Boundary Variables as shown in Figure 5.92. They are plotted as contours on the selected boundary.

 

Figure 5.91 - Avg/Max Gas Damage Power Distribution BC

Figure 5.92 - Results Display

The Average and Maximum Gas Damage power Distributions on the boundary are stored in the files: Filename_boundary_ average_gas_damage_power.txt and Filename_boundary_ max_gas_damage_power.txt respectively. They are written at the same frequency as the result files are saved.

 

Show All Distributions

The Show All Distributions switches all the following outputs to Yes:

• Avg/Max Vapor Volume Fraction Distribution
• Avg/Max Gas Volume Fraction Distribution
• Avg/Max Vapor Rate Distribution
• Avg/Max Gas Rate Distribution
• Avg/Max Vapor Damage Power Distribution
• Avg/Max Gas Damage Power Distribution



 

 

 

 

Figure 5.93 - Show All Distributions

 

Gas Volume Fraction Distribution

The total Gas Volume Fraction Distribution output is activated for a selected boundary under the Cavitation module as follows:

• Geometric Entities Panel > Boundaries > [Desired Boundary]
• Properties Panel > Model Tab > Cavitation > Output > User Select > Gas Volume Fraction Distribution > Yes

The Gas Volume Fraction Distribution for selected boundaries is output in a separate file: Filename_boundary_total_gas_volume_fraction.txt. The Total Gas Volume Fraction Distribution is output at the same frequency as the result files are saved.

 

Gas Damage Power Distribution

The total Gas Damage Power Distribution output is activated for a selected boundary under the Cavitation module as follows:

• Geometric Entities Panel > Boundaries > [Desired Boundary]
• Properties Panel > Model Tab > Cavitation > Output > User Select > Gas Damage Power Distribution > Yes

The Gas Damage Power Distribution for selected boundaries is output in a separate file: Filename_boundary_damage_power.txt. The Gas Damage Power Distribution is output at the same frequency as the result files are saved.

 

Note: All the Cavitation module distributions are available as output for Wall and Rotating Wall and other solid boundaries (such as as Conjugate Wall Interfaces). Users are recommended to turn on the time average/maximum/minimum output at the very beginning of simulation for all the variables of interest, and use the physical period (i.e. time step for one Pump pocket rotation or a complete revolution) as the “Period” whenever possible.