Research On Multi-stage Dynamic Stall Model Based On ONERA Aerodynamics

Due to the maneuverability requirements of modern high performance fighters and the structural characteristics of helicopter rotor system,aircraft often face dynamic stall problem.Because of the complexity of dynamic stall,it is impossible to use pure theoretical methods to study it effectively.At present,empirical models are often used in engineering application.ONERA,as a representative dynamic stall model,can describe the aerodynamic characteristics of airfoils under dynamic stall.However,it is still unable to capture the multi-stage peak value of aerodynamic characteristics curve under deep stall.At the same time,the application of the classical ONERA model is limited to fixed-shape airfoils,which can not meet the research needs of morphing airfoils with control surfaces.This paper mainly studies the application scope of ONERA dynamic stall model and the calculation accuracy under deep stall.First,in order to the use the ONERA model to analyze the morphing airfoils,we use Peters finite state airloads theory.Combined with the dynamic inflow model to consider the influence of wake.At the same time,based on the large oscillation data,the modified ONERA circulation equation is identified by genetic algorithm,so as to calculate the additional airloads caused by dynamic stall,and then the dynamic stall model suitable for morphing airfoil is established.Furthermore,In order to obtain the static residual of morphing airfoils,which drives the ONERA model,the static residual database of morphing airfoils is established based on the static data of reference airfoil,using generalized coordinates and a translation fitting method.For the case of deep stall and other obvious multi-stage stall phenomena,in order to model the secondary lift peak,a secondary stall circulation equation is added to the established model.This model is to be driven by a pulse and is meant to match the physics of the effect of the secondary vortex on lift.This model increases the ability to capture multi-stage lift peaks.Finally,those parts are integrated into a unified model,and the correction factors are added to obtain a time-domain unsteady airloads model suitable for dynamic stall of morphing airfoils.The calculated results are in good agreement with the experimental data,which directly verifies the validity of the model.