Receptance-based natural frequency assignment of a real fluid-conveying pipeline system with interval uncertainty

The resonance problem of an industrial fluid-conveying pipeline system can be mitigated by shifting or assigning its natural frequencies. However, the desired natural frequencies are difficult to realize using typical numerical model-based parameter optimization technologies because of the modelling errors. Herein, the first theoretical and experimental study is reported on achieving desired natural frequencies of an industrial pipeline system by using measured receptances. This research involves the one-way fluid-structure interaction of the steady flow. On this basis, this paper considers the changeability of working conditions of the pipeline system and characterizes the uncertain flow speed as an interval uncertainty. The primary framework of the classic receptance method is employed, and a novel interval-based frequency assignment method is proposed. This method inherits the advantage of the receptance methodology, in which the determination of the optimal structural modifications entirely relies on the measured frequency response functions. More especially, the obtained stiffness modifications by using the proposed method can improve the robustness of the assignment results to uncertain flow speeds, and then actually achieved values of the assigned natural frequencies have a smaller perturbation. Several numerical examples demonstrate that the proposed method provides effective results. The application of the method to the modification of a real U-shaped fluid-conveying pipeline system gives experimental evidence of its effectiveness. The effective experimental results give the confidence to use the receptance-based structural modification method to improve the dynamical behaviour of real structures.