Aerodynamic damping of an oscillating fan blade

An investigation is performed to determine the dynamic flow phenomena that dampen a fan blade's oscillation amplitude using numerical fluid structure interaction (FSI) simulations. Both a mesh-based and meshless numerical model are used to perform the FSI simulation and are compared according to their accuracy, robustness and computational cost. The meshless FSI simulation is performed by coupling the Finite Pointset Method (FPM) with a simplified 1D beam model. Experimental results from a separate investigation are used to validate the two numerical models. This paper shows that both numerical models are suitable for modelling the aerodynamic damping of an axial fan used in an air cooled condenser fan unit. The observed flow effects include the formation and shedding of leading edge vortices, downwash, tip vortices and the added mass effect. Leading edge vortices are a major damping contributor and are found to mainly depend on the blade's effective angle of attack. The mesh-based and meshless FSI simulations are able to predict the experimentally determined tip displacement within an accuracy of 13% for 5 out of 6 simulations.