Quick and accurate determination of the optimal synchrophase angle is crucial for synchrophasing control of multi-propeller aircraft with low noise.This paper proposes a novel noise prediction and optimization strateg...Quick and accurate determination of the optimal synchrophase angle is crucial for synchrophasing control of multi-propeller aircraft with low noise.This paper proposes a novel noise prediction and optimization strategy,developing a continuous and accurate noise prediction model and obtaining its minimum by solving the Hessian matrix and Fourier-Frobenius matrix.Firstly,a novel propeller noise prediction method uses acoustic simulation pressure signals and improved propeller signatures theory to accurately estimate noise for all synchrophase angles and receiving points.Secondly,a novel optimization approach is proposed to solve the analytical solution of the minimum propeller noise:(A)A noise objective function is established,and use its first derivatives’zeros and Hessian matrix to determine the function minimum.(B)A novel Euler formula transform method is proposed to convert trigonometric polynomials into algebraic polynomials,changing the zeros of the former into those of the latter.(C)Utilize the Fourier-Frobenius matrix method to solve the zeros of algebraic polynomials.To assess the computation time and accuracy,a turboprop aircraft with two six-bladed propellers was analyzed using the computational fluid dynamics and acoustic analogy method,providing acoustic pressure signals at 20 receivers for noise prediction and optimization.The Durand-Kerner and Fourier-Frobenius matrix methods were compared.Results demonstrate that improved propeller signatures theory is more accurate,and the Hessian matrix+Fourier-Frobenius matrix method is faster and more precise than the Hessian matrix+Durand-Kerner method.展开更多
In order to enable wing morphing(e.g.change in camber or folds)without incurring additional weight to the aircraft,lightweight flexible materials such as membrane are needed.However,the research on fluid-structure cou...In order to enable wing morphing(e.g.change in camber or folds)without incurring additional weight to the aircraft,lightweight flexible materials such as membrane are needed.However,the research on fluid-structure coupling of membranes has mainly focused on parachutes in low-speed conditions,while that in supersonic flow conditions is lacking.Here,the degraded shell method is proposed to study membrane deformation by using shell element,which is more effective than using membrane elements directly.A fluid-structure interaction computational framework is proposed,whereby the aerodynamic module is composed of either the piston theory or computational fluid dynamics.A rectangular membrane of length 0.4 m and width 0.6 m is investigated in supersonic conditions.The characteristics of the limit cycle and steady deformation are analyzed,considering the effects of angle of attack and dynamic pressure.It is found that the structural response exhibits significant differences under various angles of attack.Furthermore,initial relaxation of membrane has significant influence on the structural deformation.Finally,the aeroelastic scaling method for membrane structures is derived,providing guidance for the design of wind tunnel models.This study provides a theoretical foundation for the analysis and application of membrane structures under supersonic conditions in future research.展开更多
A high-precision CFD/CSD(Computational Fluid Dynamics/Computational Structural Dynamics)coupling method is developed to study the aeroelastic behavior and design the vibration reduction strategy of NTBT(New Type Blade...A high-precision CFD/CSD(Computational Fluid Dynamics/Computational Structural Dynamics)coupling method is developed to study the aeroelastic behavior and design the vibration reduction strategy of NTBT(New Type Blade-Tip)rotor with TEF(Trailing Edge Flap)technology in forward flight.In the aspect of CSD method,the closed-form dynamical governing equation is modified using Hamilton’s principle to consider the influence of the movable TEF,in which the NTBT geometric nonlinearity is considered through coordinate transformation by virtue of finite element method.In the aspect of CFD method,a moving-embedded grid method for rotor blades is developed to account for the dynamic deflection of TEF,in which the grid deformation is achieved through algebraic transformations,and a high-precision unsteady CFD method with 5th-order TENO(Targeted Essentially Non-Oscillatory)scheme is introduced to effectively simulate the rotor flowfield.Considering the computational efficiency,the loosely-coupling strategy is introduced to build up the CFD/CSD method.The validity of the coupling method is verified by comparing the computed aerodynamic loads,frequency spectrum,and structural loads with the referential or the experimental results of the typical model rotors.Based on that,the frequency,phase,and amplitude-sweeping parametric analyses of TEF are conducted thoroughly to reveal the influence mechanisms on the aeroelastic characteristics of NTBT rotor.Furthermore,an optimal control strategy is proposed to suppress the vibration intensity of hub loads,showing that the active vibration reduction method can effectively suppress the rotor hub vibratory intensity by over 40%in typical forward flight conditions.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51576097,51976089)the Funding for Outstanding Doctoral Dissertation in Nanjing University of Aeronautics and Astronautics,China(No.BCXJ24-05)the Aeronautical Science Foundation of China(No.2023L060052001).
文摘Quick and accurate determination of the optimal synchrophase angle is crucial for synchrophasing control of multi-propeller aircraft with low noise.This paper proposes a novel noise prediction and optimization strategy,developing a continuous and accurate noise prediction model and obtaining its minimum by solving the Hessian matrix and Fourier-Frobenius matrix.Firstly,a novel propeller noise prediction method uses acoustic simulation pressure signals and improved propeller signatures theory to accurately estimate noise for all synchrophase angles and receiving points.Secondly,a novel optimization approach is proposed to solve the analytical solution of the minimum propeller noise:(A)A noise objective function is established,and use its first derivatives’zeros and Hessian matrix to determine the function minimum.(B)A novel Euler formula transform method is proposed to convert trigonometric polynomials into algebraic polynomials,changing the zeros of the former into those of the latter.(C)Utilize the Fourier-Frobenius matrix method to solve the zeros of algebraic polynomials.To assess the computation time and accuracy,a turboprop aircraft with two six-bladed propellers was analyzed using the computational fluid dynamics and acoustic analogy method,providing acoustic pressure signals at 20 receivers for noise prediction and optimization.The Durand-Kerner and Fourier-Frobenius matrix methods were compared.Results demonstrate that improved propeller signatures theory is more accurate,and the Hessian matrix+Fourier-Frobenius matrix method is faster and more precise than the Hessian matrix+Durand-Kerner method.
文摘In order to enable wing morphing(e.g.change in camber or folds)without incurring additional weight to the aircraft,lightweight flexible materials such as membrane are needed.However,the research on fluid-structure coupling of membranes has mainly focused on parachutes in low-speed conditions,while that in supersonic flow conditions is lacking.Here,the degraded shell method is proposed to study membrane deformation by using shell element,which is more effective than using membrane elements directly.A fluid-structure interaction computational framework is proposed,whereby the aerodynamic module is composed of either the piston theory or computational fluid dynamics.A rectangular membrane of length 0.4 m and width 0.6 m is investigated in supersonic conditions.The characteristics of the limit cycle and steady deformation are analyzed,considering the effects of angle of attack and dynamic pressure.It is found that the structural response exhibits significant differences under various angles of attack.Furthermore,initial relaxation of membrane has significant influence on the structural deformation.Finally,the aeroelastic scaling method for membrane structures is derived,providing guidance for the design of wind tunnel models.This study provides a theoretical foundation for the analysis and application of membrane structures under supersonic conditions in future research.
基金supported by the National Natural Science Foundation of China(Nos.12102186,12472237)the Young Elite Scientists Sponsorship Program by CAST,China(No.2022QNRC001)+1 种基金the National Key Laboratory Foundation of China(No.61422202201)the Aeronautical Science Foundation of China(No.2024Z010052002)。
文摘A high-precision CFD/CSD(Computational Fluid Dynamics/Computational Structural Dynamics)coupling method is developed to study the aeroelastic behavior and design the vibration reduction strategy of NTBT(New Type Blade-Tip)rotor with TEF(Trailing Edge Flap)technology in forward flight.In the aspect of CSD method,the closed-form dynamical governing equation is modified using Hamilton’s principle to consider the influence of the movable TEF,in which the NTBT geometric nonlinearity is considered through coordinate transformation by virtue of finite element method.In the aspect of CFD method,a moving-embedded grid method for rotor blades is developed to account for the dynamic deflection of TEF,in which the grid deformation is achieved through algebraic transformations,and a high-precision unsteady CFD method with 5th-order TENO(Targeted Essentially Non-Oscillatory)scheme is introduced to effectively simulate the rotor flowfield.Considering the computational efficiency,the loosely-coupling strategy is introduced to build up the CFD/CSD method.The validity of the coupling method is verified by comparing the computed aerodynamic loads,frequency spectrum,and structural loads with the referential or the experimental results of the typical model rotors.Based on that,the frequency,phase,and amplitude-sweeping parametric analyses of TEF are conducted thoroughly to reveal the influence mechanisms on the aeroelastic characteristics of NTBT rotor.Furthermore,an optimal control strategy is proposed to suppress the vibration intensity of hub loads,showing that the active vibration reduction method can effectively suppress the rotor hub vibratory intensity by over 40%in typical forward flight conditions.
