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Homework Help: Constants definition - turbulent vel. profile

  1. May 13, 2012 #1

    jkr

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    1. The problem statement, all variables and given/known data

    Hello!

    I need some help with a problem:

    Problem: Turbulent flow beteween parallel flat plates.

    It is defined:

    [ tex ] \tau = \mu \frac{d\bar{u}}{dy}-\rho\bar{u'v'} [ \tex ]

    The exercise gives that [ tex ] \tau = a y [ \tex ] and [ tex ] \rho\bar{u'v'} = \frac{by}{c+dy^2} [ \tex ], where [ tex ] a,b,c,d[ \tex ] are constants.

    I need to know: How can I choose these constants? I'm looking for an aproximate solution.

    Until now, I used just the no-slip condition at [ tex ] \pm H [ \tex ] and [ tex ] \frac{du(y=0)}{dy}=0 [ \tex ]

    Tks for the help!

    2. Relevant equations
    [ tex ] \tau = \mu \frac{d\bar{u}}{dy}-\rho\bar{u'v'} [ \tex ]
    [ tex ] \tau = a y [ \tex ]
    [ tex ] \rho\bar{u'v'} = \frac{by}{c+dy^2} [ \tex ]

    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 14, 2012 #2

    NascentOxygen

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    Staff: Mentor

    Hi jkr! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    I'm astonished that you posted your question with its non-functioning itex formatting instructions. I have fixed them for you. Don't include unnecessary spaces inside the [...] instruction. And its [/tex] NOT [\tex].

    I can't help you with a fluidics question, but now maybe someone else can. :smile:
     
    Last edited by a moderator: May 6, 2017
  4. May 14, 2012 #3

    jkr

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    Tks a lot for this! =D
     
  5. May 14, 2012 #4

    jkr

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    Hi again,

    If [tex] \rho \bar{u'v'} =0 [/tex] at [tex] y = \pm H [/tex] then the model [tex] \rho \bar{u'v'}=\frac{by}{c+dy^2} [/tex] doesn't work because [tex] b=0.[/tex]
    However, for the case
    [tex] \rho \bar{u'v'} =\frac{by+ey^3}{c+dy^2},[/tex] How does it work?

    []s
     
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