Balancing quietness and performance: New trade-off optimization framework enhances propeller design for next-gen aircraft
image: The high-efficiency aerodynamic and aeroacoustic optimization framework comprises the following key modules: 1) Shape parameterization, which transforms the baseline geometry into a set of design variables; 2) CFD-CAA solver, used to evaluate aerodynamic and aeroacoustic objectives and constraints; 3) Unsteady adjoint solver, which computes multi-objective sensitivities; and 4) Gradient-based optimizer, which utilizes these sensitivities to iteratively refine the design. Based on this framework, a multi-objective trade-off optimization study is performed by adjusting the weighting factors between aerodynamics and aeroacoustics. This enables the exploration of their influence on the resulting optimal configurations and provides deeper insight into the design principles behind high-efficiency and low-noise propellers.
Credit: Chinese Journal of Aeronautics
Propeller-driven aircraft are re-emerging as critical players in the push toward sustainable aviation, particularly in Urban Air Mobility (UAM) and hybrid-electric propulsion systems. However, a long-standing challenge has persisted in propeller design: enhancing aerodynamic efficiency often results in increased noise levels, and vice versa.
To overcome this issue, a research team led by Associate Professor Shuanghou Deng at the College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, China, has developed a novel unsteady adjoint-based multidisciplinary optimization framework. This method integrates high-fidelity Computational Fluid Dynamics (CFD) with advanced Computational Aeroacoustics (CAA) through an innovative on-the-fly hybrid solver and a unified sensitivity analysis system. Their study, recently accepted by the Chinese Journal of Aeronautics, marks a significant step forward in balancing aerodynamic and aeroacoustic performance for propeller blades.
“Previous approaches typically prioritized either aerodynamic efficiency or noise reduction, rarely achieving both,” said Shuanghou Deng. “Our framework enables accurate and efficient evaluation of both objectives and their sensitivities simultaneously, facilitating optimized designs without compromise one for the other.”
The team applied their method to optimize a three-blade propeller operating under realistic flight conditions. By adjusting the weighting between aerodynamic efficiency and noise suppression during the optimization process, the researchers obtained the optimal configuration that reduced radiated noise while also achieving modest gains in propulsive efficiency.
One of the key findings lies in the geometric modifications suggested by the optimization. Propeller blades featuring reduced chord length and radial dimensions, combined with the introduction of distinctive "rotated-S" shaped airfoil profiles near the tip region, showed a remarkable ability to redistribute aerodynamic loads and suppressed tonal noise—without incurring a significant aerodynamic penalty.
“This design not only mitigates far-field noise but also enhances aerodynamic control through improved load distribution,” Shuanghou Deng added.
The study further demonstrates that incorporating different weighting factors into a multi-objective optimization function is a viable strategy for exploring the design principles behind efficient and quiet propellers. When the weighting factor is set between 0.25 and 0.5, the framework yields an optimal balance between performance and noise suppression.
The researchers validated their results through comprehensive simulation and acoustic analysis, showing consistent reductions in overall sound pressure levels across multiple observer angles and frequencies. The proposed method provides both a theoretical foundation and a practical design tool for the next generation of environmentally friendly aircraft.
Looking ahead, the team plans to extend the framework to more complex systems, including counter-rotating open rotors and eVTOL configurations. They are also exploring the integration of machine learning-based surrogate models to further accelerate the optimization process.
Other contributors to the study include Haolin Zhi, Tianhang Xiao, Ning Qin, and Jingliang Guo.
Original Source
Haolin ZHI, Shuanghou DENG, Tianhang XIAO, Ning QIN, Jingliang GUO. Trade-off between propeller aerodynamics and aeroacoustics using unsteady adjoint-based design optimization[J]. Chinese Journal of Aeronautics, 2025, https://doi.org/10.1016/j.cja.2025.103481.
About Chinese Journal of Aeronautics
Chinese Journal of Aeronautics (CJA) is an open access, peer-reviewed international journal covering all aspects of aerospace engineering, monthly published by Elsevier. The Journal reports the scientific and technological achievements and frontiers in aeronautic engineering and astronautic engineering, in both theory and practice. CJA is indexed in SCI (IF = 5.3, top 4/52, Q1), EI, IAA, AJ, CSA, Scopus.