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Old   April 14, 2009, 12:02
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Hi All, I am observing some disturbances in my simulation, and I would like to test the discretization scheme. The problem is that I don't know how to change the tolerances of the method or some other parameter. Can I only change between First order or Second Order BKW Euler? Or can I change the tolerances for each case?
I am trying to observe the wave propagation and its reflection using as input a displacement as a step function. when I apply such input as mesh displacement, some disturbances are generated and those run fast then the sound velocity.
I am using air as ideal gas in the domain, and as input I am using a step function with 10nm of amplitude.
Can anybody help me? Tips are also welcome...

Thanks
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Old   April 14, 2009, 20:40
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Glenn Horrocks
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Hi,

More discretisation options are available in CFX than are shown on the GUI. You will need to use the command file to access them. To see everything available look in the RULES file, in (CFX ROOT)/etc, under the advection scheme heading.

Glenn Horrocks
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Old   April 16, 2009, 03:03
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Hi Mr. Horrock,
I looked in that file but I couldn't see information about tolerances. Is it dependent of some other parameter? My doubt is about the tolerance settings for the transient scheme.

Thanks for helping.
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Old   April 16, 2009, 08:10
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Glenn Horrocks
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Hi,

There is no "tolerance" specifically for the temporal discretisation. The numerical tolerance of relevance is the equation residuals and for some cases the imbalances. You should always test the effects of different convergence levels to ensure you have adequate convergence anyway.

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