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Merging, Diverging, and Routing Flow
Merging and diverging flow
Proportional mode
With the Proportional mode, you define in a table what the proportion of flow through each branch will be. The proportion for each branch is defined in the table relative to each of the other branches. For instance, a value of 2 for the top outflow branch and 4 for the bottom out- flow branch would indicate that the bottom branch should have twice the amount of flow as the top branch. If a particular branch's proportion has been defined to be blank or <= 0, the effec- tive rate for that branch is set to 0 and the flow is stopped for that branch.
☞ See “Merge blocks in Proportional mode” on page 439 for options when a Merge block is part of an empty loop.
This mode uses a fixed flow rule where the effective rate at each branch is required to meet the proportion defined by the table. Consequently, if the flow through one or more of the branches is blocked or starved, the effective rates for all branches will be set to zero and all flow through the block is halted.
Proportional Mode Diverge model
In this example, flow coming from the Infinite Source is evenly distributed between the Diverge block’s three outflow branches. This occurs because the proportions in the table in the Diverge block’s dialog have been set to 1:1:1. With this proportion, the effective rate across all three branches is required to be the same – an identical amount of flow must pass through each branch.
The initial constraining rate for the three
Valve blocks is set to 100. However, the Shut-
down block forces Valve 1's constraining rate
to alternate between 0 and 100 as the model
runs. This has an impact on the effective rate
for all three branches. When the constraining
rate for Valve 1 switches to 0, the outflow from all three branches goes to 0 even though the constraining rate for Valves 2 and 3 is still equal to 100. This is because the Diverge block must enforce its ratio, which is 1:1:1 in this example.
Proportional Mode Merge model
This model is the mirror image of the Proportional Mode Diverge model discussed above. While all three Valve blocks limit the supply of flow from the source tanks at an initial con- straining rate of 100, the Shutdown block forces the constraining rate in Valve 1 to alternate between 0 and 100. As in the previous model, when the constraining rate in Valve 1 switches to 0, the effective rates for all three branches become 0 because the Merge block is in Propor- tional mode and must enforce the 1:1:1 equality it is set to.
Priority mode
The Priority mode allows you to attach priorities to the inflow branches of the Merge block and the outflow branches of the Diverge block. These priorities only impact the effective rates assigned to the branches when discrepancies arise between the upstream flow supply and the downstream flow demand; otherwise they are ignored.
Proportional Mode Diverge model
Discrete Rate

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