Optimization-driven computational method for critical ice shapes on two-dimensional airfoils

The efficient calculation of critical icing conditions and ice shapes is of paramount importance for aircraft safety, design, and certification. Traditional methods, which select discrete points within the flight and icing envelopes and employ sensitivity analysis, often fail to identify optimal solutions and suffer from low accuracies. Leveraging the independently developed ice calculation software NNW-ICE and incorporating an optimization method, a calculation approach for critical icing conditions and critical ice shapes of two-dimensional airfoils was devised. This approach utilizes self-defined characteristic parameters of the ice shapes. Specifically, a meshless potential flow solver within NNW-ICE was developed to compute the flow field. A genetic algorithm was utilized to optimize the critical icing conditions and critical ice shapes within the icing envelope specified in FAA icing design envelopes (14 CFR Parts 25 and 29, Appendix C). To demonstrate the practical application of the proposed method, it was applied to calculate the critical ice shape of a NACA0012 airfoil. The effectiveness of the method was validated through comprehensive ice geometry and aerodynamic performance analyses. Furthermore, the critical icing conditions for 20 different types of two-dimensional airfoils were calculated, and the range of the critical icing envelope for two-dimensional airfoils was preliminarily determined based on the icing envelope specified in FAA icing design envelopes (14 CFR Parts 25 and 29, Appendix C).