Comparison of Experimental and Operational Modal Analysis on a Flexible Silicone Tube Conveying Fluid

Abstract

AbstractThe flexible tubes are light in weight, corrosion-resistant and chemically inert to fluids. Also, as it offers low bending stiffness compared to the axial tensile stiffness, it can be rolled into a single tube and can be fabricated without any joints for making long pipes. The above properties make flexible tubes a good replacement for metal tubes in many fluid conveyance applications. A very minute disturbance in the fluid conveying flexible tubes can lead to a severe to and fro energy interaction among the fluid and structure which may lead to cause intense tube vibrations. But compared to the metal tubes, flexible tubes need only very minimal energy to get excited. Hence small undulations in fluid flow through the flexible tube can generate severe small internal fluid pulsations which look similar to some disturbances or excitation. These disturbances sometimes lead to the flow-induced vibrations in flexible tubes. If the flow induced vibrations frequency matches with any of the natural frequencies of the pipes conveying fluid, resonance will occur. Hence the design of flexible tubes and its supports rely on the accurate identification of the fundamental frequencies as well as on the understanding of the influence of flow induced vibration on the fundamental frequencies of the flexible tubes conveying fluid. This paper deals with a comparative study on the various experimental methods used in the dynamic analysis of flexible tubes.KeywordsExperimental modal analysisOperational modal analysisFlexible structuresBeat frequencyPre-stretch