Bernhard Manhartsgruber, Rudolf Scheidl,
"On 3D Viscid Periodic Wave Propagation in Hydraulic Systems"
, in D N Johnston, K A Edge: Power Transmission and Motion Control - PTMC 2006, Seite(n) 109-120, 9-2006, ISBN: 08-6197-135-3
On 3D Viscid Periodic Wave Propagation in Hydraulic Systems
Sprache des Titels:
Power Transmission and Motion Control - PTMC 2006
It is well known that periodic waves in a straight pipe exhibit small dynamic boundary layers.
A nice explanation of the characteristics of this boundary layer has been given by Gittler, Kluwick, and Brummayer using singular perturbation techniques and asymptotic expansions. They split the whole flow into a compressible bulk flow without any friction (omitting viscosity) which characterises the flow in nearly the whole cross section and a dynamic boundary layer which is strongly effected by viscosity. Their results tell that the effect of the
boundary layer on the bulk flow in the centre is given by radial velocity components which work similarly to flexible walls which hinder the flow of an inviscid fluid in its interior if their tangent plane is not parallel to the main flow direction. On the other hand, the usual derivation of the transmission line equations does neglect any radial velocity component but uses the shear stresses at the boundary layer. Yet, the results of both approaches are nearly identical. This raises the question of the true physical background of the effect of the boundary layer.