An Experimental Study of Fluid-Structure Interaction in Basic in-line Arrangements of Cylinders
Résumé
Heat exchangers are very common equipment used innumerous industrial facilities all around the world. Throughoutthe years, engineers have learned how to build them, how tomake them more robust and efficient and how to develop andadapt them for a wide variety of applications. Yet the factremains that the dynamic motion of a flexible cylindersubmitted to a cross flow inside a tube bundle responds tophysical principles that are still to be fully understood [1]. Morespecifically, the prediction of whether or not a tube will exhibitdamping-controlled instability (flutter) cannot be achievedbetter than with an acceptable margin of safety, let alonedealing with unknown geometries or conditions of operation.We offer here to go back to the start and to observe thisinstability experimentally in even simpler geometries underlow-turbulent monophasic flow. For this work, we had a smallhydraulic loop at our disposal. It lets water flow at Reynoldsnumbers from 3000 to 10000 through a working sectioncomprising one to three tubes (or a full 4x5 array), amongwhich only one is flexible. A lot of different patterns have beentested, notably cylinders side-to-side along the flow ortransverse to it and cylinders in tandem, vibrating either in thelift or in the drag direction. This experimental setup allowed usto plot the tube frequency, its apparent damping and itsamplitude according to the reduced velocity. In the end, we aimto provide the community with some supplementaryexperimental data and hopefully shed some light on thebehavior of these oscillating tubes.