# Did I calculate the boundary layer thickness correctly?

1. Dec 8, 2013

### PhyIsOhSoHard

1. The problem statement, all variables and given/known data
A flat plate moves in water (20°C) in the direction of the plate at a speed of 1 m/s. What is the boundary layer thickness 0.1 meter downstream of the plate?

2. Relevant equations
Reynolds number:
$Re_x=\frac{xU_∞}{\nu}$

Boundary layer thickness for laminar flow:
$\frac{\delta}{x}=\frac{5.0}{\sqrt{Re_x}}$

3. The attempt at a solution
Reynolds number is:
$Re_x=\frac{xU_∞}{\nu}=\frac{1m/s\cdot 0.1m}{9\cdot 10^{-7}}=1.1\cdot10^5$

Boundary layer thickness:
$\frac{\delta}{x}=\frac{5.0}{\sqrt{Re_x}}=\frac{5.0}{\sqrt{1.1\cdot10^5}}=0.015$

$\frac{\delta}{x}=0.015⇔$

$\delta=0.015\cdot 0.1m=0.0015m=1.5mm$

2. Dec 9, 2013

Anyone?