# Model is structurally singular

**URL:** <https://community.wolfram.com/t/model-is-structurally-singular/20678>\
**Category:** Questions\
**Tags:** engineering, system-modeler\
**Created:** [September 7, 2022, 11:48am UTC](https://community.wolfram.com/t/model-is-structurally-singular/20678 "2022-09-07T11:48:54Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![mikaeelshaikh](https://avatars.discourse-cdn.com/v4/letter/m/ecc23a/32.png) [@mikaeelshaikh](https://community.wolfram.com/u/mikaeelshaikh)\
**Post date:** [September 7, 2022, 11:48am UTC](https://community.wolfram.com/t/model-is-structurally-singular/20678/1 "2022-09-07T11:48:54Z")

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I was trying to simulate the below given problem albeit it was globally balanced but it displayed an error when I tried simulating the model.  
The error that came is

```
** Error: Model is structurally singular, the following equations do not allow to solve for required variables:
    pipe.flowModel.m_flows[1] = pump.m_flow_nominal /* Solvable for: pipe.flowModel.m_flows[1] 
    volume.m = 995.586 * volume.V /* Solvable for: volume.m 
    der(volume.m) = -pipe.flowModel.m_flows[1]  
    Solvable for: volume.m, pipe.flowModel.m_flows[1] 

```

Validation of model water\_mod completed with 1 error.  
I tried changing the mass flow rate values but still couldn’t solve this error.  
Any help will be appreciated.  
Model is given below:

 ![error.PNG](https://global.discourse-cdn.com/wolfram/original/3X/b/1/b1a4aad4a3cd5a25550bdfb35e82dca4dfbb5242.png)

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**Author:** ![ankitn](https://yyz1.discourse-cdn.com/wolfram/user_avatar/community.wolfram.com/ankitn/32/25931_2.png) [@ankitn](https://community.wolfram.com/u/ankitn)\
**Post date:** [September 8, 2022, 7:38am UTC](https://community.wolfram.com/t/model-is-structurally-singular/20678/2 "2022-09-08T07:38:28Z")

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Can you attach the model?

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<div class="post-metadata">

**Author:** ![mikaeelshaikh](https://avatars.discourse-cdn.com/v4/letter/m/ecc23a/32.png) [@mikaeelshaikh](https://community.wolfram.com/u/mikaeelshaikh)\
**Post date:** [September 8, 2022, 8:51am UTC](https://community.wolfram.com/t/model-is-structurally-singular/20678/3 "2022-09-08T08:51:07Z")

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[@Ankit Naik](https://community.wolfram.com/web/ankitn) You can go through this model which I created for transfer of Water.

[water\_test.mo](https://community.wolfram.com/uploads/short-url/eod2vWuIqWNb0FaLCzygyzvrryW.mo) (6.89 KB)

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<div class="post-metadata">

**Author:** ![mikaeelshaikh](https://avatars.discourse-cdn.com/v4/letter/m/ecc23a/32.png) [@mikaeelshaikh](https://community.wolfram.com/u/mikaeelshaikh)\
**Post date:** [September 12, 2022, 11:34am UTC](https://community.wolfram.com/t/model-is-structurally-singular/20678/4 "2022-09-12T11:34:00Z")

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[@Ankit Naik](https://community.wolfram.com/web/ankitn) Hi, Any Update?

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<div class="post-metadata">

**Author:** ![ankitn](https://yyz1.discourse-cdn.com/wolfram/user_avatar/community.wolfram.com/ankitn/32/25931_2.png) [@ankitn](https://community.wolfram.com/u/ankitn)\
**Post date:** [September 13, 2022, 9:53am UTC](https://community.wolfram.com/t/model-is-structurally-singular/20678/5 "2022-09-13T09:53:57Z")

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I am not sure what is triggering the error.

I guess it might be due to the absence of a source component and improper initial values. I have attached a working model here: [https://amoeba.wolfram.com/index.php/s/FraFRbYNy2NAXYQ](https://amoeba.wolfram.com/index.php/s/FraFRbYNy2NAXYQ)