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successive ratio type in Gambit

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Old   March 13, 2008, 16:03
Default successive ratio type in Gambit
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Em
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Dear CFD staff Please how working or mathematical formula for successive ratio type in Gambit mesh. if bar length 1m and i need 10 nodes and successive ratio type 1.2 How working this???? thank you for help me emad
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Old   March 13, 2008, 18:11
Default Re: successive ratio type in Gambit
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Carlos
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At the bottom of the edge mesh window, right click on edge spacing and change to cell count. Put 10 as your value for the number of nodes and select ratio of 1.2.

Carlos.
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Old   March 13, 2008, 23:19
Default Re: successive ratio type in Gambit
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Em
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thanks Carlos I know to work this steps, But I need mathatical formula for sucessive ratio type. emad
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Old   March 14, 2008, 04:00
Default Re: successive ratio type in Gambit
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Carlos
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Mathematically its just a series expression. If the ratio is 1.2 then the distance between the 2nd and 3rd node is 1.2 multiplied by the distance between 1st and second node.

So, if your distance is say 1m, the first distance is x and you want to use 5 nodes then the formula would be:

1 = x + x(1.2) + x(1.2^2) + x(1.2^3) + x(1.2^4)

So you just need to find x and you have your first distance. You'll need a maths book to figure this out, its been too long since I did this sort of thing!

Carlos.
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Old   March 14, 2008, 07:55
Default Re: successive ratio type in Gambit
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Em
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Thank you very much Dear Carlos Please If using double successive ratio can be using this formula for half lenght and second ratio in other side. Please help me to calculate the value x if you have some time to help me. With best regards emad
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Old   March 14, 2008, 14:50
Default Re: successive ratio type in Gambit
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Carlos
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Emad,

If using the double successive ratio then I think its the same formula on the other side. To find x you just need to find a mathematician to help! I don't know how but it is straightforward for a maths guy.

I don't understand why you need to find x though, surely you can just play with the controls and change the spacing and expansion ratio until you get the correct number of elements in your space. This is how mesh people do it...

Carlos.
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