# Creating a time variant velocity formula for a inlet

**URL:** <https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798>\
**Category:** Project Support\
**Created:** [March 2, 2018, 2:36pm UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798 "2018-03-02T14:36:43Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![damiduz](https://www.simscale.com/forum/letter_avatar/damiduz/32/5_5575768a8748004e209b776fc1b2916d.png) [@damiduz](https://www.simscale.com/forum/u/damiduz)\
**Post date:** [March 2, 2018, 2:36pm UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/1 "2018-03-02T14:36:43Z")

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> **[dummy new ren by damiduz | SimScale](https://www.simscale.com/projects/damiduz/dummy_new_ren/)**
>
> half section run | Simulation project by damiduz

for this, i need to add a variant velocity like starting from 0 and gradually increase up to 100 kmh-1 within 5 minutes time. can someone help me with the setting up the settings?

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**Author:** ![Kai\_himself](https://www.simscale.com/forum/letter_avatar/kai_himself/32/5_5575768a8748004e209b776fc1b2916d.png) [@Kai\_himself](https://www.simscale.com/forum/u/Kai_himself)\
**Post date:** [March 2, 2018, 6:41pm UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/2 "2018-03-02T18:41:00Z")

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Hey @damiduz,  
i think you need a csv file like this, or you use a linear funktion ?

 ![tesz](https://www.simscale.com/forum/uploads/default/original/3X/f/8/f837f41d6288cb1c22aaa63cdb51824a10a2d1f1.jpg)

Greetz Kai

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**Author:** ![jousefm](https://www.simscale.com/forum/user_avatar/www.simscale.com/jousefm/32/34908_2.png) [@jousefm](https://www.simscale.com/forum/u/jousefm)\
**Post date:** [March 2, 2018, 8:23pm UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/3 "2018-03-02T20:23:04Z")

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Thanks for your input @Kai_himself!! 🙂

He is right @damiduz, you can either use a CSV table upload or define a function (f(t,x,…)) to prescribe time dependent BC. Let us know if you have any further questions!

Enjoy your weekend!

Jousef

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**Author:** ![damiduz](https://www.simscale.com/forum/letter_avatar/damiduz/32/5_5575768a8748004e209b776fc1b2916d.png) [@damiduz](https://www.simscale.com/forum/u/damiduz)\
**Post date:** [March 3, 2018, 1:31am UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/4 "2018-03-03T01:31:06Z")

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how can i create a CSV file ?

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**Author:** ![Get\_Barried](https://www.simscale.com/forum/user_avatar/www.simscale.com/get_barried/32/20599_2.png) [@Get\_Barried](https://www.simscale.com/forum/u/Get_Barried)\
**Post date:** [March 3, 2018, 9:11am UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/5 "2018-03-03T09:11:26Z")

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Hi @damiduz,

You can do so in Microsoft Excel. Make sure to save the file as CSV.

Cheers.

Regards,  
Barry

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**Author:** ![damiduz](https://www.simscale.com/forum/letter_avatar/damiduz/32/5_5575768a8748004e209b776fc1b2916d.png) [@damiduz](https://www.simscale.com/forum/u/damiduz)\
**Post date:** [March 4, 2018, 1:38am UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/6 "2018-03-04T01:38:15Z")

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i am going to run this for 4000 itterations. do i have to define all 4000 one by one.

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**Author:** ![Get\_Barried](https://www.simscale.com/forum/user_avatar/www.simscale.com/get_barried/32/20599_2.png) [@Get\_Barried](https://www.simscale.com/forum/u/Get_Barried)\
**Post date:** [March 5, 2018, 5:47am UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/7 "2018-03-05T05:47:00Z")

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Hi @damiduz,

According to what I see in @Kai_himself’s post, yes it does seem like so. Excel has functions which will help with making this job easy so it shouldn’t be too much of a hassle.

Cheers.

Regards,  
Barry

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**Author:** ![damiduz](https://www.simscale.com/forum/letter_avatar/damiduz/32/5_5575768a8748004e209b776fc1b2916d.png) [@damiduz](https://www.simscale.com/forum/u/damiduz)\
**Post date:** [March 5, 2018, 7:59am UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/8 "2018-03-05T07:59:19Z")

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what it the function ?

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**Author:** ![Kai\_himself](https://www.simscale.com/forum/letter_avatar/kai_himself/32/5_5575768a8748004e209b776fc1b2916d.png) [@Kai\_himself](https://www.simscale.com/forum/u/Kai_himself)\
**Post date:** [March 5, 2018, 9:29am UTC](https://www.simscale.com/forum/t/creating-a-time-variant-velocity-formula-for-a-inlet/81798/9 "2018-03-05T09:29:39Z")

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I think a linear funktion y=m_x+b, (1/3)_(x\*t),x=1 so you got a linear funktion from 0 to 100kmh in 300 seconds (5 min)

Greetz Kai