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Homework Help: How do you I calculate the Laminar Boundary Layer Y in meters

  1. Jul 20, 2011 #1
    1. The problem statement, all variables and given/known data

    How do you I calculate the Laminar Boundary Layer Y in meters with Blasius Equation?
    I have an expression for U (m/s) and u/U and u(m/s) and also eta=0.1, 0.2....5.2. I am wondering how one could calculate the y laminar boundary layer (m), the y buffer boundary layer (m), the ln y and the y turbulent boundary layer (m)... I know that I need different expression to calculate these...can someone tell me what expressions and how I get the y laminar/buffer/ln y/y turbulent?

    This is an example of the sheet I have:
    U (m/s) u/U u (m/s) Eta y lam (m) y buff (m) ln y y turb (m)
    252.7 0 0 0 ? ? ? ?
    252.7 0.047 11.8 0.1 ? ? ?
    252.7 0.0939 23.728 0.2 ? ? ? ?
    etc....

    2. Relevant equations

    I do think I can use the equation

    Eta= y*sqrt(U/nu*x)
    for ylaminar...but I have already found the tabulated data for Eta from Rosenhead's book in Laminar Boundary Layers...and I have the following X values:
    X=...
    25.91
    27.27
    28.94
    30.08
    32.64
    34.62
    36.19
    39.13
    41.99
    43.44
    44.57
    45
    44.57
    43.44
    41.99
    39.13
    36.19
    34.62
    32.64
    30.88
    28.94
    27.27
    25.91

    The following Eta values
    h
    0
    0.1
    0.2
    0.3
    0.4
    0.5
    0.6
    0.7
    0.8
    0.9
    1
    1.1
    1.2
    1.3
    1.4
    1.5
    1.6
    1.7
    1.8
    1.9
    2
    2.2
    2.4
    2.6
    2.8
    3
    3.2
    3.4
    3.6
    3.8
    4
    4.2
    4.4
    4.6
    4.8
    5
    5.2

    and U=252.7 m/s and u/U accordingly.

    3. The attempt at a solution
    For ylaminar do I only solve for y in the equation Eta= y*sqrt(U/nu*x)?
    If so, how what are the expressions for ybuffer, ln y (meaning which y should I take the log function on, the laminar, buffer or turbulent) and yturbulent? Can anyone pls help me? I am unsure about how to see when the transition starts so I can go from ylaminar to ybuffer/ turbulent based on my y values...I am grateful if anyone can help me. Thanks
     
  2. jcsd
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