Creating a simple master and slave system

Two important features of hydraulic Discrete Partitioning are:

• it is based on wave dynamics in hydraulic pipes, modeled using Lax- Wendroff submodels,

• it can lead to great speedups when running simulations of large systems.

We will consider a very simple model already shown in the Hydraulic library manual.

Figure 5: A very simple hydraulic system

This is certainly not a large system and there are no wave dynamics in the model. With simple, steady state models of the pump and motor it would be inappropriate modeling to include wave dynamics. However, to allow you to see how discrete partitioning systems work we will put wave dynamics into this small system.

It makes little sense as a hydraulic model and you will certainly not get any speedups, but you should be able to construct and run the example in 10-15 minutes.

When we use discrete partitioning, we must divide the complete system up into a master and one or more slaves. To do this, we do not use discrete hydraulic line submodels HLLW0, HLLW1 and HLLW2. Instead, a combination of component submodels HLLWPIPE0 with HLLWCNXFLOW0 and/or HLLWCNXEFFORT0 are to be used. The corresponding icons are found in the first hydraulic category:

Figure 6: HLLWPIPE0 and HLLWCNXFLOW0/HLLWVNXEFFORT0 icons

The larger of these two icons is associated solely with the submodel HLLWPIPE0. This is known as the discrete hydraulic line center section submodel.

The smaller icon is associated with both HLLWCNXFLOW0 and HLLWCNXEFFORT0. They are known as discrete hydraulic line end-piece submodels. They differ only in causality. Normally you select submodels for the rest of the system and allow Simcenter Amesim to decide if HLLWCNXFLOW0 or HLLWCNXEFFORT0 should be used. In the current system, the submodels used are as follows:

Figure 7: Submodels used

Procedure

1. Construct the example below.

Figure 8: Conventional Simcenter Amesim system

As indicated by the rectangular outlines, we can think of this system as being composed of three sub-systems.Save the system as SimpleHydr.ame.

Use Premier submodel and default parameters for all submodels.

To see the wave dynamics, use a final time of 0.1 seconds, and an appropriate print interval.

This is a conventional Simcenter Amesim system, and you are now going to convert it to a master and slave system.Make sure you save the system in its final form.

In the next part of this exercise, you are going to remove one of these sub-systems (labeled Sub-system 1 in the example) and convert it to the following slave system: Figure 9: Simple Hydraulic system slave

The discrete hydraulic line end-piece submodels (HLLWCNXFLOW0 or HLLWCNXEFFORT0) must be included in the slave.

The slave system does not contain a fluid properties icon. It inherits its properties from the master system.

The remaining part of the original system becomes the master and still includes sub-systems 2 and 3: Figure 10: Simple Hydraulic system master

2. Create the master and slave system.

Cut and paste the pump sub-system (slave) into a new system and save it as SimplePumpSlave.ame.

Add a master block to the slave system.

Add a slave block to the master system and save it as SimpleMaster.ame.

It is a good idea to keep the original so that you can compare results.

Make sure the slave system is complete with all components connected and associated with submodels. Save it as SimplePumpSlave.ame.

We could also go to Parameter mode and change parameters if needed.

Close the slave system, but keep the master open.

3. Define the slave in the master.

We now have a master system and a slave system.

To associate the slave with its master, we switch to Parameter mode and use the menu Configure > Slave system settings.

The following dialog box opens: Figure 11: Setting the slave system path

Click in the Original slave system path field and then click the browse button to locate the slave system .ame file.

Select the slave system file SimplePumpSlave.ame, and click Open in the browser dialog box.

Note that the Slave name field will be set to SimplePumpSlave. If necessary, you can change this by editing the field.

Click again somewhere in the Slave Systems dialog box to confirm the path.

Highlight the single entry in the list.

Note how the corresponding submodel has a green label attached.

Click Load to associate the slave with the master.

Click Ok.

Simcenter Amesim opens the slave system alongside the master system. The slave system is now dependent on the master system. When the slave system window is selected in Simulation mode, the run buttons are not available. This is because the runs must be initiated by the master system. Figure 12: Slave run buttons

Note The system SimplePumpSlave.ame is still closed. What we see is a local copy of this system.

4. Make the master the active system and run the simulation.

5. Compare plots from the discrete partitioning system with those from the conventional simulation.

Figure 13: Conventional versus master/slave system

The plot shows the pressure at the junction next to the relief valve. You need to zoom in a lot to separate the curves. What happened during the run?

Two Simcenter Amesim systems were running in parallel.

They were communicating with each other at intervals during the simulation.

These intervals are defined by the ends of the Lax-Wendroff steps.

If you have a 2-core (processor) machine, it is possible that both cores/processors were used.