Suppression of oscillatory fluid forces in cylinder wake: Optimal jet control position designed through resolvent analysis

The flow around a circular cylinder is a typical case of unstable separated flow, and controlling its stability has long been a focus of flow control research. This study proposes an optimal control parameter design method based on resolvent analysis, which provides precise design criteria for jet position through effective gain. First, resolvent analysis of cylinder wake flow is conducted. The effective gain is obtained by formulating the velocity excitation corresponding to the local tangential jet, imposing it on the forcing mode, and subsequently multiplying it by the resolvent gain. Subsequently, a steady tangential jet is applied to the optimal control position guided by the effective gain, achieving complete suppression of oscillatory loads. Concurrently, the sensitivity of jet effective control position parameters is validated by computational fluid dynamics. Finally, the effective gain accurately identified the optimal jet control position for different Reynolds numbers ( R e ≤ 120 ). It is observed that the optimal control position shifts upstream with increasing Reynolds number. This study demonstrates that resolvent analysis can accurately capture the critical sensitivity characteristics of flows, providing precise and direct guidance for optimal control position parameter design.