Rayleigh Dissipation function for aerodynamic Drag

Hi

I'm trying to model the drag effects in using Lagrange Mechanics and trying to include the effects of aerodynamic drag.

I've read up on the Rayleigh Dissipation functions in Greenwood's "Advanced Dynamics" and a few other books but they always provide the Rayleigh function for drag forces proportional to velocity.

However, I am looking for the function describing a force proportional to the square of velocity.

Can anyone point me to any books or papers on this?

Thanks in advance,
Amir