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Cap (G)

Gas port terminator with zero flow

  • Library:
  • Simscape / Foundation Library / Gas / Elements

  • Cap (G) block


The Cap (G) block represents a perfectly insulated terminus for a gas network branch. There is no mass or energy flow through the cap.

You can use this block to terminate gas ports on other blocks that you want to cap. This is not necessary because if you leave a conserving port unconnected, the physical network sets all the Through variables at that port to 0. However, terminator blocks improve diagram readability.

You can also use this block to set the initial pressure and temperature at a node.


To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables and Initial Conditions for Blocks with Finite Gas Volume.



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Gas conserving port where the mass flow rate and energy flow rate are both equal to zero.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2016b

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Behavior changed in R2019b