# How to calculate Reynolds number?

How do I calculate the Reynolds number of a wing with wing chord,1.2m and speed of 60km/h

One way is to see what the following NASA links have to say about it and possibly using the calculator they have at the bottom of either page.

https://www.grc.nasa.gov/WWW/K-12/airplane/viscosity.html

The similarity parameter for viscosity is the Reynolds number. The Reynolds number expresses the ratio of inertial forces to viscous forces. From a detailed analysis of the momentum conservation equation, the inertial forces are characterized by the product of the density $\rho$ times the velocity $V$ times the gradient of the velocity $dV/dx$. The viscous forces are characterized by the viscosity coefficient $\mu$ times the second gradient of the velocity $d^2V/dx^2$. The Reynolds number $Re$ then becomes:

$$Re = (\rho \cdot V \cdot dV/dx) / (\mu \cdot d^2V/dx^2)$$

$$Re = (\rho \cdot V \cdot L) / \mu$$

where $L$ is some characteristic length of the problem.

and

The dynamic viscosity coefficient divided by the density is called the kinematic viscosity and given the Greek symbol $\nu$

$$\nu = \mu / \rho$$

$$Re = V \cdot L / \nu$$

The units of $\nu$ are length^2/sec.

https://www.grc.nasa.gov/WWW/K-12/airplane/reynolds.html

The Reynolds number expresses the ratio of inertial (resistant to change or motion) forces to viscous (heavy and gluey) forces.

• I've edited the post for you, but please consider revising my edit and adding any extra information you think should be added. – Federico Aug 2 '18 at 8:02