Pressure/flow relationships in collapsible tubes; effects of upstream pressure fluctuations

An experimental investigation has been made on the pressure/flow behaviour of a collapsible tube. Of particular interest are the effects of upstream pressure fluctuations on the mean pressure/flow relationships. These mean pressure/flow relationships were found to exhibit features generally similar to the steady-flow situation, including flow limitation where the flow rate becomes independent of the driving pressure during the tube-collapsed phase. However, the tube collapsed under a higher downstream pressure and the maximum flow rate was reduced, when either the frequency or amplitude of the upstream pressure fluctuations was increased.