Rayleigh dissipation function
In physics, the Rayleigh dissipation function, named for Lord Rayleigh, is a function used to handle the effects of velocity-proportional frictional forces in Lagrangian mechanics. It is defined for a system of particles as
The force of friction is negative the velocity gradient of the dissipation function,. The function is half the rate at which energy is being dissipated by the system through friction.
As friction is not conservative, it is included in the Qj term of Lagrange's equations.
