Question

Can you determine the critical distance along a flat surface?

Answer 1

Explanation:

Consider a fluid of density, ρ moving with a velocity, U over a flat plate of length, L.

Let the Kinematic viscosity of the fluid be ν.

Let the flow over the fluid be laminar for a distance x from the leading edge.

Now this distance is called the critical distance.

Therefore, for a laminar flow, the critical distance can be defined as the distance from the leading edge of the plate where the Reynolds number is equal to 5 x $10^{5}$

And Reynolds number is a dimensionless number which determines whether a flow is laminar or turbulent.  

Mathematically, we can write,

    Re = $\frac{\rho .U.x}{\mu }$

or 5 x $10^{5}$ =  $\frac{\rho .U.x}{\mu }$ ( for a laminar flow )

Therefore, critical distance

$x=\frac{5\times 10^{5}\times \mu }{\rho \times U}$

So x is defined as the critical distance upto which the flow is laminar.