This study numerically investigates the wake control of a circularcylinder by dual splitter plates symmetrically attached at the rear surface,parallel to the flow. The effect of these plates on the wake transition tothree-dimensional structures was examined via a Floquet stabilityanalysis. Simulations for attachment angles of 20 and 40 degrees with aconstant splitter plate length were carried out with the Reynolds numberin the range of 150 to 350. The results show that the splitter plates havea crucial effect on the onset of secondary instabilities. In comparison toan isolated cylinder, two new modes are found, which are referred to asmode A' and mode B'. Mode A' is similar to mode A, but with a quitelong critical wavelength. Mode B' shares the same spatiotemporalsymmetries with mode B but has a distinct spatial structure. Furthermore,the ordering of occurrence of the unstable modes can be modified fordifferent geometric configurations. The onset characteristics of thetransition modes are analyzed and discussed in detail.
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