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convergence check:grid and time-step size

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Old   August 15, 2012, 06:53
Default convergence check:grid and time-step size
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Dear all,

I want to do a convergence check for the spatial resolution (grid) and the temporal resolution (time-step-size) of my simulations. I want to do some simulations using pulsatile flow and compare them with simulations using the average velocity of this pulsatile profile. Furthermore I want to do some simulations with the profile upscaled about 2 times.
Do I have to do the convergence checks for all of this situations or is it enough to do them with the (let's say) most dramatic situation: pulsatile, upscaled (large velocity and velocity-gradients)?
And is there kind of a rule how to proceed with these 2 convergence checks: how many grids, how many time-steps, how to combine them?
I am really thankful for any idea and help!
Lilly
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Old   August 15, 2012, 07:57
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Filippo Maria Denaro
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Quote:
Originally Posted by Lilly View Post
Dear all,

I want to do a convergence check for the spatial resolution (grid) and the temporal resolution (time-step-size) of my simulations. I want to do some simulations using pulsatile flow and compare them with simulations using the average velocity of this pulsatile profile. Furthermore I want to do some simulations with the profile upscaled about 2 times.
Do I have to do the convergence checks for all of this situations or is it enough to do them with the (let's say) most dramatic situation: pulsatile, upscaled (large velocity and velocity-gradients)?
And is there kind of a rule how to proceed with these 2 convergence checks: how many grids, how many time-steps, how to combine them?
I am really thankful for any idea and help!
Lilly

be careful in taking convergence check by fixing h or dt... the monotone convergence study should be performed fo vanishing ratio dt/h, when you fix one parameter you must be sure that the value is very very small otherwise your convergence will be altered when the error reaches that magnitude order
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