Numerical Analysis of a Coaxial Counter-Rotating Rotor Blade System

Calculates the Thrust and Power characteristics for a ducted and un-ducted coaxial rotor system

This is an extension of my single rotor analysis code.

The function is based on the mathematical treatment of rotating rotors in "Principles of Helicopter Aerodynamics" by Dr. J.Gordon Leishman

The numerical method does this by using Blade Element Momentum Theory (BEMT) to calculate the inflow along the length of the blade, then using that inflow and Lifting Line theory to calculate the local lift and drag on the blade.

It then knows the outflow of the upper rotor and uses that as the inflow for the lower rotor after modelling the correct wake contraction characteristics.

The thrust and power are then calculated from the local values and summed along the length of the blades to give the totals.

This numerical method works for multiple blade configurations through the input parameter BChar, which is detailed in the header of the m-file, although at this stage it requires that both the upper and lower rotors have the same characteristics.

This function has been used to form the basis of a multidisciplinary optimisation used on a coaxial rotor UAV that was designed and built in 2008.