These Simulink blocks contain transfer functions that model the pressure and flow transients for axisymmetric 2D viscous flow of a compressible fluid in a straight rigid circular cross section pipelines. Three models are available: (1) pressures at the ends (2) flow rates at the ends (3) pressure at one end and flow rate at the other Filtering is incorporated to reduce numerical oscillation (Gibbs phenomenon). See J. Dyn. Systems, Meas. & Control vol 122 (2000) pp. 153-162.