Validation study for prediction of iced aerofoil aerodynamics

Ice accretions can significantly change the aerodynamic performance of wings and rotor blades. Significant performance degradation can occur when ice accreations cause regions of separated flow, to predict this change implies, at a minimum, the solution of the Reynolds-Averaged Navier-Stokes equations. This paper presents validation for two generic cases involving the flow over aerofoil sections with added synthetic ice shapes. Results were obtained for two aerofoils, namely the NACA 23012 and a generic multi-element configuration. These results are compared with force and pressure coefficient measurements obtained in the NASA LTPT wind-tunnel for the NACA 23012, and force, PIV and boundary-layer measurements obtained at DNW for the multi-clement case. The level of agreement is assessed in the context of industrial requirements.

Model reduction for nonlinear aerodynamics and aeroelasticity using a Discrete Empirical Interpolation Method

A novel surrogate model is proposed in lieu of Computational Fluid Dynamics (CFD) solvers, for fast nonlinear aerodynamic and aeroelastic modeling. A nonlinear function is identified on selected interpolation points by<br/>a discrete empirical interpolation method (DEIM). The flow field is then reconstructed using a least square approximation of the flow modes extracted<br/>by proper orthogonal decomposition (POD). The aeroelastic reduce order<br/>model (ROM) is completed by introducing a nonlinear mapping function<br/>between displacements and the DEIM points. The proposed model is investigated to predict the aerodynamic forces due to forced motions using<br/>a N ACA 0012 airfoil undergoing a prescribed pitching oscillation. To investigate aeroelastic problems at transonic conditions, a pitch/plunge airfoil<br/>and a cropped delta wing aeroelastic models are built using linear structural models. The presence of shock-waves triggers the appearance of limit<br/>cycle oscillations (LCO), which the model is able to predict. For all cases<br/>tested, the new ROM shows the ability to replicate the nonlinear aerodynamic forces, structural displacements and reconstruct the complete flow<br/>field with sufficient accuracy at a fraction of the cost of full order CFD<br/>model.