Simcenter STAR-CCM+ How to extract from 3D CFD simulation component behavioral model to feed system simulation
2019-10-15T07:10:13.000-0400
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Summary
Details
Purpose
Although the 3D CFD software packages focus mainly on simulating free-stream flow of fluids, and the interaction of fluids with surfaces, they are not usually set up for system simulation purposes. Incorporating 3D CFD assumptions within Simcenter Amesim by using co-simulation methods leads to high fidelity solutions but faces CPU times drawbacks.To decrease design time scale while maintaining accuracy from 3D CFD technology, there is an opportunity to use 3D CFD as a virtual test-bench to derive characterized components for use in Simcenter Amesim system simulations. It is convenient when considering complex geometries, specific operating ranges that are beyond available components from the thermo-fluid components.
The Simulation Based Characterization tool (SBC) makes it possible for the power of 3D CFD technology to be brought to Simcenter Amesim system simulation. It entails the use of Simcenter STAR-CCM+ to perform multiple 3D CFD simulations on dedicated conditions to cover the range of use. The resulting behavioral model is represented by look-up tables which can be imported as parameters in dedicated Simcenter Amesim components.
Description
To illustrate the workflow, the characterization of a simple orifice is performed. From this characterization, the flow vs. pressure drop characteristic is extracted.A prerequisite is to set-up the 3D CFD model so that Simcenter STAR-CCM+ solves the fluid flow through the orifice on static points for the defined operating range.
Figure 1: 3D geometry of the orifice
Simcenter STAR-CCM+ model
The simulation file contains predefined objects:
- mesh operations
- physics models
- initial conditions (in the physics continuum and at the inlet boundary)
- regions and boundaries
- parameters and reports
Visualizing the volume mesh
The generated mesh is the following. A refinement is done close to the orifice.Figure 2: Volume mesh (cut-off plane)
Figure 3: Volume mesh
Inspecting study inputs
There are two kinds of study input: design parameters and global parameters.Two parameters related to the geometry of the orifice can be modified: the radius of the orifice and the radius of the main pipe.
Figure 4: Design parameters
Two parameters allow you to set up the conditions in the Region and the Boundaries: the initial pressure and the initial temperature.
Figure 5: Global parameters
Inspecting study outputs
Study outputs are related to the Reports.The following variables are computed from the physics values on the surface of boundaries:
- Density Volume Average: returns the average density in the region.
- Mass Flow Inlet: returns the average mass flow rate on the boundary Inlet.
- Mass Flow Outlet: returns the average mass flow rate on the boundary Outlet.
- Error: returns the difference between Mass Flow Outlet and Mass Flow Inlet.
- Mean Mass Flow: returns the mean value between Mass Flow Outlet and Mass Flow Inlet.
- Mean Flow: returns the mean value of the volumetric flow rate.
- Pressure Drop: returns the pressure difference between the pressure at boundary Inlet and the pressure at boundary Outlet.
Figure 6: Reports
Design study
When loading the simulation file within Simulation Based Characterization tool, the inputs and the outputs defined as parameters and reports in the simulation file are listed. None of them are selected and the design matrix is empty.Figure 7: List of inputs/outputs
The goal is to create the flow characteristic as a function of the pressure drop and fluid temperature at the inlet of the orifice.
Then a sweep study is performed on the inlet pressure and inlet temperature to cover the operating range.
The variations are the following:
- Inlet pressure takes the values 5, 10, 15, 20, 25, and 30 in bar.
- Inlet temperature takes the values 20, 40, 60, and 90 in degC.
For the outputs, Pressure Drop, Mean Mass Flow, and Mean Flow are selected.
Figure 8: Design matrix
Once the study is set-up, the simulation can be run.
Results
At the end of simulation, you have all the results of the study in the Results matrixFigure 9: Result matrix
Depending on your needs or the components you use in your Simcenter Amesim model, you can create a flow characteristic as a function of the pressure drop for one temperature or a flow characteristic map that considers both the pressure drop and the temperature.
Creating a cluster of 2D map flow characteristic
From the Graphical User Interface, we just need to select the table format in agreement with Simcenter Amesim and the variables that are used for the axes.
- Select M1D Table as Table Format.
- Select Pressure Drop as X1 axis.
- Select InletTemperature as X2 axis.
- Select Mean Flow as Y values.
Figure 10: Flow map
Once created the table can be saved in your current project folder.
Conclusion
This simple example shows how to extract from 3D CFD results the characteristics of a component. These characteristics are saved in a table format used by Simcenter Amesim. They can be set as parameters of standard physics libraries or read within signal components table type of.For more information, you can consult the user’s manual related to Simulation Based Characterization within Simcenter Amesim.
Check also the demo of the usage of Simulation Based Characterization to get the characteristics of a flapper valve that is integrated within a transmission model.
About the author:
Jerome Guillemin is senior product manager for all pre- and post-processing features in Simcenter Amesim at Siemens Digital Industries Software.