Abstract In this work, the influence coefficient method together with a sliding plane method was used for an efficient analysis of fan acoustic flutter. The method requires the computational domain to be split to two zones: the rotating fan zone and the stationary intake zone. The subdomain interface is connected using the sliding plane method. The split of the domain is necessary for a stable solution. The time-accurate dual-time stepping method was applied for solving the blade vibration-induced unsteady flow. To demonstrate this method, a wide chord fan with two bell mouths of different duct lengths was chosen as the test case. The effects of acoustic reflection from the bell mouth on the fan aerodynamic damping were investigated by varying fan blade vibration frequency at 80% speed. The acoustic reflection has a noticeable influence on the fan aerodynamic damping only when the blade vibration frequency is close to the duct resonance frequency. The results also indicate that the slightly cut-on scattered modes impact the fan aerodynamic damping as well. The proposed method is validated by comparing with traveling wave method solutions.
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