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the difference profile in the empty domain

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Old   August 24, 2006, 06:07
Default the difference profile in the empty domain
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justin
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Hello,

My study is on neutral atmospheric boundary layer wind tunnel. the inlet boundary was well known as U(z)=u*ln(z/z0)/k, outlet as outflow,sides and top as symmetry. z0, k and eps were got from the previous wind tunnel test.

Realisable k-eps,two layer wall funciton,smooth wall, structured mesh and second order were used in the empty domain.

After convergence, there was a large difference between inlet profile and outlet profile. Then grid was refined, but the problem still existed.If I use the cyclic conditoin between inlet and outlet, the constant profile can be got, but it was not what I wanted.

How can I achieve the consant profile in the empty domain?

your comments will be appreciated

Justin

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Old   August 25, 2006, 06:32
Default Re: the difference profile in the empty domain
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justin
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Now I found the reason, which was related to the epsilon. the well known equation eps=u*/(kz)made this problem, but it is difficult to solve. If we use the equation eps=Cu^(3/4)*k^(3/2)/l, eps looks like a constant, but accturally it is a variable with the vertical. also l and Cu is a changeable constant with the condition.

How do you describe the eps? please give any comments.

Thanks

Justin
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