# Pressure Coefficient

The pressure coefficient is a dimensionless quantity of interest to aerodynamicists.

The pressure coefficient is defined as:

*p - p _{inf} = q_{inf} . C_{p}*

where:

** C_{p}** is the dimensionless pressure coefficient

**is the pressure due to the movement of the body through the fluid**

*p***is the free stream fluid pressure**

*p*_{inf}**is known as the gauge pressure**

*p - p*_{inf}**is the free stream fluid dynamic pressure from Bernoulli's equation:**

*q*_{inf}*q _{inf} = 1/2 rho_{inf} . V_{inf}^{2}*

where:

** rho_{inf}** is the free stream fluid density

**is the free stream fluid speed**

*V*_{inf}

**Pressure Coefficient Comparison Between Calculation (lines) and Experiment Around an Airfoil**

You will often see pressure coefficient plots of numerical calculations compared with wind tunnel experimental data as a means to judge the accuracy of the numerical technique used. This type of comparison is often referred to as a validation.