Assessment and Optimization of Dynamic Stall Semi-empirical Model for Pitching Aerofoils

Dynamic stall is a phenomenon affecting aerofoils in unsteady flows which is particularly relevant in the rotary-wing field. Semi-empirical models are simplified tools to simulate this phenomenon, especially during preliminary design phases and for aeroelastic assessments. However, they need a large number of tuning parameters to provide reliable estimations of unsteady airloads. To face this problem, a parameter identification procedure based on sequential resolutions of optimization problems using a genetic algorithm is developed and it is applied to the state-space formulation of a modified version of the so-called "Second Generation” Leishman-Beddoes model. The effects of the optimal parameters on the model prediction capabilities are discussed and the variability of the parameters with reduced frequency is studied. The estimations of the unsteady airloads obtained by applying the optimization of parameters show a great improvement in the correlation of the experimental data if compared to the predictions obtained by using the parameters provided in the literature, especially for pitching moments where the negative peaks are very well described. These improvements justify the need for optimization to set the parameters.