f 500[Hz] Incident wave frequency
T 1/f Incident wave period
omega 2*pi*f Angular frequency
lambda_min c0/f Minimum wave length
c0 343[m/s] Speed of sound
k 2*pi/lambda_min Wave number
D0 2*dr+2*dw Total pipe diameter
kD0 k*D0 Wave number times tube diameter
dvisc 0.22[mm]*sqrt(100[Hz]/f) Viscous boundary layer size