DLM- and CFD-Based Continuous Turbulence Encounter for a High Aspect Ratio Configuration

Abstract

The avoidance of persistent contrails through cruise altitude adjustments is considered a promising measure for reducing aviation's climate impact. However, changes in flight altitude modify atmospheric conditions, turbulence characteristics, and aerodynamic loading, requiring a reassessment of turbulence load predictions for future climate-optimized flight operations. This study investigates continuous turbulence encounter loads for the high-aspect ratio DLR-F25 research aircraft using both the Doublet Lattice Method (DLM) and frequency domain Computational Fluid Dynamics (CFD). The CFD-based approach is first validated against time-domain CFD simulations and subsequently applied to evaluate sectional loads and load collectives for different cruise flight levels and operating conditions. Both aerodynamic methods predict the same fundamental frequency range of the dominant aeroelastic modes. However, significant differences are observed in the detailed modal responses and particularly in the prediction of torsional moments. While DLM generally predicts increasing loads with increasing turbulence intensity and dynamic pressure, CFD results indicate a more complex dependence of loads on altitude, airspeed, and dynamic pressure.