Effect of various structures on the shell-side flow over coil tube bundles

•A detailed investigation of the shell-side flow over coil tube bundles with various structural parameters was conducted using the DES method, which was verified by previous studies.•The evolution of the flow structures over time and the influence of the parameters on the flow structures were analyzed.•The time–frequency information of the flow was discussed using PSD, CWT, and MGDA methods.•The vortex shedding frequency bands and St were revealed, and it was found that the flow on the shell side is a combination of multiple flow modes.