Defining Fluids in SolidWorks Flow Simulation

Flow Simulation allows you to analyze the flow of up to ten fluids of different types (Liquids, Gases/Steam, Non-Newtonian Liquids and Compressible Liquids) in the same project. Fluids mixing can be analyzed as well, but mixing fluids must be of the same type (All gases, for example). In the Default Fluid dialog box, you can specify the default fluids and default fluid type to be assigned for all fluid regions. After the project is created, you can specify different fluid types for specific fluid regions using the Fluid Subdomain feature. Fluid regions with different types of fluids must be separated from each other by solid region(s).  If there is no appropriate fluid listed in the Fluids list, you can define a new substance in the Engineering Database.

To specify fluids required for an analysis:

1.     In the Fluids list, click ‘+’ at the left of the fluid type name to display the list of fluids of this type available in the Engineering Database. The fluid types are: Gases, Liquids (Newtonian viscous incompressible liquids), Non-Newtonian liquids, Compressible liquids, Real Gases and Steam.  If you discover that the required fluid is not available, click New and add the new fluid to the Engineering Database.

2.     Double-click the desired fluid in the Fluids list.
- OR -
Select a fluid from the Fluids list and click Add.

·        If you have added fluids of DIFFERENT types to the Project fluids list, you must select the Default Fluid Type. Only fluids of this type will be available to be assigned as default project fluids. The selected fluid type is assigned by default for all fluid regions in the analysis. After the project is created, you can then specify another fluid type for a specific fluid region using the Fluid Subdomain feature.

·        If you have added more than one fluid of the SAME type to the Project fluids list, you again can select which of them will be assigned as the default fluid for all fluid regions. After the project is created, you then have two options: You can assign other fluids for a specific fluid region using the Fluid Subdomain feature OR you can define the fluids' different Substance Concentrations (For when you have a gas that is 78% Nitrogen, 21% Oxygen, and 1% Argon for example).  For these multiple fluids, the relative concentrations can be specified either by Mass fractions or Volume fractions of the different fluids.

·        Default fluids’ concentrations are specified in the Initial Conditions section of the Wizard, or the Boundary Condition Property Manager near the bottom.

3.     Specify which Flow Characteristics are required for the analysis.

·       By default, the flow can be either laminar or turbulent or with transition (depending on the flow characteristics). Under Flow type, you can consider the flow as laminar only in the entire Computational Domain by selecting Laminar Only.  You can also consider the Flow as Turbulent Only. If you have specified Non-Newtonian liquids or Compressible liquids as the project's fluid type, the Laminar Only flow type will be selected automatically to consider the flow in all fluid regions as laminar. After the project is created, you can specify another fluid type and, therefore, another flow type for a specific fluid region using the Fluid Subdomain feature.

·       Select the High Mach number flow check box if you want to analyze high-velocity gas flows (flow Mach number is greater than about 3 for steady-state and 1 for transient analyses). The High mach number option is applied for the entire computational domain and cannot be changed for an individual fluid region. You cannot select the High Mach number flow option if some Real Gas is selected as one of the Project fluids or the calculation of relative Humidity is enabled.

·       Select the Humidity check box if you want to analyze a flow of gas, or mixture of gases, taking into account its relative humidity.

·       If you want to consider cavitation in your analysis, select the Cavitation check box. Two cavitation models are available in Flow Simulation: engineering model for pre-defined water and simplified isothermal cavitation model for user-defined liquids with the Cavitation effects enabled in the Engineering Database. Both cavitation models consider fluids with a single liquid component only, so Cavitation is unavailable if more than one liquid is selected as Default fluid. If you select Cavitation for a user-defined liquid, the flow will be considered as isothermal and all thermal conditions specified in the project will be ignored. You cannot select Cavitation for a user-defined liquid when Heat conduction in solids is enabled.

4.     Click Next or click a button on the Navigator pane to switch to the corresponding dialog box of the Wizard.

After the project is created, you can change the default project fluids as well as the default fluid type and flow characteristics under Fluids in the General Settings dialogue box.  Simply right click on the Input Data folder in the Flow tree.