# the difference profile in the empty domain

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 August 24, 2006, 06:07 the difference profile in the empty domain #1 justin Guest   Posts: n/a 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

 August 25, 2006, 06:32 Re: the difference profile in the empty domain #2 justin Guest   Posts: n/a 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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