Page 45 - Continuous Process Modeling Quick Start Guide
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Concepts & Terminology 41
Mixing block types
all the left-most blocks first. If you use this order, be sure that blocks that calculate values are to the left of the blocks which need those values. Otherwise, there will be a one step delay in calculating the values.
Custom order
‘Use caution when changing from Flow order.
In continuous modeling, there are some situations with multiple feedback loops that do not automatically settle into the desired flow order solution. This occurs because there are multiple solutions that solve the DAG (Directed Acyclic Graph) ordering problem, and it is possible for the less desired solution to be picked.
To solve this ordering problem, start with the model set to Flow order and then change the order for a few selected blocks using the Model > Set Simulation Order command.
☞ To use the Custom order option effectively, the Model > Show Simulation Order command should be checked so that the user can see which blocks need a changed order.
The Set Simulation Order command is not enabled unless Custom order is selected in the Simu- lation Setup dialog and a block is selected on the model worksheet.
In the Set Simulation Order dialog, you can enter a new order number for the selected block and it will be moved into that position in the simulation order.
Note that any custom order is lost if either Flow order or Left to right order is selected again.
Mixing block types
You can use continuous blocks, such as
those from the Value library, in discrete event and discrete rate models. You cannot, however, use discrete event or discrete rate blocks in continuous models. All blocks in the discrete event and discrete rate libraries require an Executive block that changes the timing of the model to event timing.
Connections to multiple inputs
In a continuous model, you can connect from one output connector to as many input connectors as you want. Multiple inputs from one output is useful when many blocks need the results of a preceding block. For instance, if you have one output connector connected to four input connectors, the model might look like the image at right.
One value output connected to four inputs in a continuous model

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