The beam impedance of monopole modes in a pipe with periodic, smooth and shallow corrugation has been calculated. The approach uses an orthogonal TM field expansion with Bessel functions and an impedance boundary condition, which takes into account resistive wall effects. The approach is valid for corrugations with period lengths larger, smaller and of the same order as the free space wavelengt...

In this paper a previously developed theoretical model of the measurement process performed by a transittime ultrasonic anemometer is applied to a fluid flowing through a circular section pipe. This model considers the influence of the shift of the acoustic pulse trajectory from straight propagation due to the flow on the measured speed. The aim of this work is to estimate the errors induced in...

The recent theoretical discovery of families of travelling wave solutions in pipe flow (Faisst & Eckhardt 2003; Wedin & Kerswell 2004; Hof et al. 2004) at Reynolds numbers lower than the transitional range naturally raises the question of their relevance to the turbulent transition process. Here a series of numerical experiments are conducted in which we look for the spatial signature of these ...