Webster's equation with curvature and dissipation
  Wave propagation in curved tubular domains is considered. A general version of Webster's equation is derived from the scattering passive wave equation. More precisely, it is shown that planar averages of a sufficiently smooth solution of the wave equation satisfy the corresponding Webster's equation when the latter includes additional control signals determined by the solution. 
Teemu Lukkari and Jarmo Malinen
math.AP math.DS