Getting started

CFD getting started The first step towards co-simulating an Simcenter Amesim model with an external CFD software package is to set up the interface within Simcenter Amesim itself.

In this section, you will be given a walkthrough of the basic workflow for setting up a co-simulation interface – here, the context will be that of a T-junction through which hydraulic fluid is driven. It is this T-junction which we would like to represent with the help of a different program, using the interface blocks of Simcenter Amesim.

Note

The interface set up in this section will be between Simcenter Amesim and another running GUI of Simcenter Amesim, not with a CFD code. This is done for the sake of simplicity, in order to give an explicit illustration of how the interface is made – you  will have to follow the exact same steps in order to create the interface with a CFD code, as illustrated in later sections.

Figure 9: The model intended for co-simulation

Users are strongly advised to carry out a preliminary study of their system in its purely uncoupled state. In the context of our model, this means leaving the T-junction submodel in place as a first step, and simulating the system as it is. This will make it possible to ensure that the model has been constructed properly, and that the results are as expected.

An added bonus of this first stage is the fact that this preliminary simulation will provide data for comparison with the results from the 1D/3D CFD co-simulation later on. Thus, you will be able to directly view the changes that arise in your results as a result of co-simulation.

Next, you must remove the submodel in question, and place sensor and actuator blocks in order to exchange the correct physical quantities with the third-party program. As will be detailed in the Motivations section, and since it provides the user with much more control over the interface’s implementation, the block you should use is a UserCosim interface block from the Generic Co-simulation library.

Figure 10: Creating a “UserCosim” interface block

While setting up the interface, as shown below, users must be aware that the input ports (into the interface) are numbered from top to bottom, whereas the output ports (from the interface) are numbered from bottom to top.

Figure 11: Assigning the interface block type and port names

All that remains now is to connect the newly created interface block to the sensors and actuators created earlier. In the case of this example, Simcenter Amesim will provide pressures, whereas the third-party software will provide flow rates.

Figure 12: The sketch after the interface block has been inserted – inputs and outputs of T-junction are added for illustration

When the user enters Simulation mode in Simcenter Amesim, the interface block will be detected. Since it is of the UserCosim type, a DLL (or shared library for Unix users) is created automatically when the model is compiled.

Note

Please refer to the Limitations section for more information about cross-platform and cross-architecture compatibility.

The next step of the process is to link the external program to Simcenter Amesim using the specific interface code, the complexity of which varies with the intricacy of the co-simulation use-case – see Simple examples for more information.   The user can now start a simulation. This will allow him to view the results either in the Simcenter Amesim GUI or in the companion software. This includes the variables exchanged between the two software packages as well as the variables available on each side.