# Operation could not be created issue

**URL:** <https://www.simscale.com/forum/t/operation-could-not-be-created-issue/100804>\
**Category:** CAD Mode Support\
**Created:** [March 1, 2026, 4:04pm UTC](https://www.simscale.com/forum/t/operation-could-not-be-created-issue/100804 "2026-03-01T16:04:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Angusangus](https://www.simscale.com/forum/letter_avatar/angusangus/32/5_5575768a8748004e209b776fc1b2916d.png) [@Angusangus](https://www.simscale.com/forum/u/Angusangus)\
**Post date:** [March 1, 2026, 4:04pm UTC](https://www.simscale.com/forum/t/operation-could-not-be-created-issue/100804/1 "2026-03-01T16:04:58Z")

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Trying to create a subtraction of a car with an external flow volume. When making the target body the flow region and the tool, the car, I get this issue. (Error code: LgTnELKD) Url: [qweqwe | SimScale Workbench](https://www.simscale.com/workbench/?pid=8247213480685646787&dcs=2d0315c6-1d2a-4298-b6c9-1530c1be6229)

 ![image](https://www.simscale.com/forum/uploads/default/original/3X/2/9/293618cd5644eb3cde840f6559cff9107f9bc7cd.png)

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**Author:** ![igaviano](https://www.simscale.com/forum/user_avatar/www.simscale.com/igaviano/32/73967_2.png) [@igaviano](https://www.simscale.com/forum/u/igaviano)\
**Post date:** [March 2, 2026, 3:44pm UTC](https://www.simscale.com/forum/t/operation-could-not-be-created-issue/100804/2 "2026-03-02T15:44:10Z")

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Hi @Angusangus, thanks for posting!

The problem is that you’re trying to perform a Boolean Subtract operation on a hollow space. If you hide all solids but the flow region, you’ll notice that a cavity will be present in the same place as your car geometry:

 ![image](https://www.simscale.com/forum/uploads/default/original/3X/c/b/cb4205ec06441be4621dc8badb4e31caa92f276a.png)

This happens because the External Flow Volume operation already performs the Boolean subtract automatically as part of the process.

Now, the correct workflow to remove the solid parts to run the simulation is to use the “Delete body” feature instead:

 ![image](https://www.simscale.com/forum/uploads/default/original/3X/1/b/1b2d5e94b0a612ec4f7d471c908fbed5089cb0ee.png)

Cheers  
Igor