Abstract
Effects of a flexible wall on the flow disturbance are studied experimentally using thin-walled rubber tubes of different lengths conveying steady inflow of water. Experiments are performed for the tubes surrounded by air, water and glycerol. Fluctuations of the flow velocity and displacements of the outer tube wall are measured by a hot-film anemometer and a gap senser around the laminar-turbulent transition. The results show that when the tube length and surrounding media are varied, the critical Reynolds number for rubber tubes are higher than that for rigid tubes in each case, and suggest that the wall flexibility can suppress the occurrence of turbulence in the flow. Negative correlations between the maximum frequency of flow velocity and wall displacement are observed from the spectrum analysis. The results also suggest that there is likely an optimum condition of frequency of wall vibrations which produce maximum reduction of flow disturbance. Then, it can be inferred that the wall vibration plays an important role to govern the occurrence and growth of disturbance of flow.
