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July 29, 2004, 15:52 
Problem with momentum equation

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July 29, 2004, 16:56 
Re: Problem with momentum equation

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To neglect the stress, you may need to do some dimensional analysis. For example, if the Reynolds number is very small, you may be get rid of the inertia terms(the stress tensor), then you have to keep the viscosity term. Suggest to use the viscosity of Argon, length scale and velocity for the dimensional analysis. I am not sure this will help. But usually that is the way people use to simplify the equations.


August 2, 2004, 16:55 
Re: Problem with momentum equation

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Are you even in the continuum limit? At P = 1 mTorr, your meanfreepath should be on the order of 10 cm at room temperature.


August 2, 2004, 18:09 
Re: Problem with momentum equation

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Im interested in pressures above 5 mTorr(magnetron sputtering normally takes place from 5 to 40 mTorr). A rough stimation gives a free path of 1.5 cm. The typical distaces considered are 5 to 10 cm, which in turn validates the use of a continuum approach. I am using a MC model for the energetic particles which are impossible to model in a continuum model. Right now I just want to simplify the momentum equation so it is not that complicated to couple with a diffusionconvection equation.


August 5, 2004, 20:04 
Re: Problem with momentum equation

#5 
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You should calculate a Knudsen number to check the limit.


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