Open Access. © 2022 F. O. Hamdoon et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 License Curved and Layer. Struct. 2022; 9:396ś402 Research Article Farouk Omar Hamdoon, Alaa Abdulhady Jaber*, and Enass H. Flaieh An overset mesh approach for a vibrating cylinder in uniform flow https://doi.org/10.1515/cls-2022-0178 Received May 01, 2022; accepted Aug 18, 2022 Abstract: This paper has numerically investigated two- dimensional laminar fow over a vibrating circular cylinder. Numerical simulation is performed using the dynamic over- set mesh method available in commercial software ANSYS FLUENT 19.0. A simple harmonic motion is applied to simu- late the cylinder vibration using the user-defned function (UDF) tool in FLUENT. To examine the accuracy and the capability of the present overset mesh approach, two test types of cylinder vibration are simulated: crossfow and in- line vibrations. All simulations are performed at a constant Reynolds number (Re = 100) to predict the occurrence of synchronization or lock-in phenomenon. For the case of crossfow vibration, it is observed that lock-in occurs with cylinder oscillation frequency near the Strouhal frequency of the fxed cylinder. However, for the inline vibration, lock- in occurs near twice the Strouhal frequency of the fxed cylinder. Furthermore, in the case of crossfow oscillation, the frequency content in the lift coefcients’ time history is successfully linked to the phase portraits’ shape and the vorticity feld. The simulation results are consistent with the available published data in the literature. This indicates that the present numerical technique is valid and capable of modeling fows with moving structural systems. Keywords: Cylinder vibration, laminar fow, overset mesh, Fast Fourier transform, crossfow, inline vibration 1 Introduction The fow problem around oscillating bodies has numerous appeals, both in terms of fow feld physics and actual engi- *Corresponding Author: Alaa Abdulhady Jaber: Mechanical Engineering Department, University of Technology- Iraq, Baghdad, Iraq; Email: alaa.a.jaber@uotechnology.edu.iq Farouk Omar Hamdoon: College of Engineering, University of Wasit , Wasit, Iraq Enass H. Flaieh: Mechanical Engineering Department, University of Technology- Iraq, Baghdad, Iraq neering applications. The nonlinear interplay between the body motion and the incident fow produces a variety of intriguing phenomena, including vortex lock-in, hysteresis and bifurcation, modifcation of vortex shedding patterns, and chaotic wake behavior. From an engineering stand- point, this subject is particularly pertinent to wind engineer- ing, ofshore exploration, maritime structures, and nuclear and conventional power plants. One of the main interesting fow phenomena around a vibrating structure is lock-in or synchronization between the vortex shedding and struc- tural vibration frequencies. Even though the cylinder is in a stable condition throughout a given range of Reynolds numbers, a cylinder in a uniform fow causes unsteady fow. For a stationary circular cylinder, unsteady fow is detected as periodic vortex shedding, referred to as the von Kármán vortex street, and the Reynolds number determines the Strouhal frequency of vortex shedding. The cylinder oscil- lates due to the vortex-induced force acting on it as a result of this periodic vortex shedding. Inherently, a forced os- cillating circular cylinder has two frequency components: the applied driving frequency and the Strouhal frequency corresponding to the fow across the circular cylinder. At a particular oscillation state, these two frequency compo- nents can cause synchronization . During lock-in, the vortex shedding frequency deviates from the Strouhal shedding frequency of a fxed structure and becomes identical to the frequency of the vibrating structure. Lock-in can amplify the response of the vibrating structure resulting in fatigue failure. Hence, cylindrical structures such as cooling tow- ers, heat exchanger tubes, chimney stacks, nuclear reactor fuel rods, ofshore structures, etc., may collapse due to the lock-in phenomenon. Consequently, several strategies have been implimented to control and suppress the efect of vor- tex induced vibration [1ś4]. Numerous experimental and computational studies have been conducted to investigate the fow over a circular cylinder undergoing forced vibrations. Bishop and Has- san [5] conducted experimental work to study how the fuid forces are infuenced by forcing a circular cylinder to vibrate in a crossfow (transverse) direction. Under the infuence of lock-in, the lift force frequency synchronizes with the vi- brating cylinder frequency. Koopmann [6] investigated the fow over a circular cylinder undergoing forced crossfow