Blending the agility of aerial drones with the covert capabilities of underwater submersibles,the aerial-aquatic rotorcraft has garnered substantial interest due to their unparalleled capacity to traverse both air and...Blending the agility of aerial drones with the covert capabilities of underwater submersibles,the aerial-aquatic rotorcraft has garnered substantial interest due to their unparalleled capacity to traverse both air and water.Nevertheless,a critical hurdle for these vehicles lies in mitigating the adverse effects of repeatedly transitioning between these environments,particularly during water-surface takeoffs.Currently,research on the interference caused by rotors approaching water surfaces remains limited.This paper introduces a novel adaptive rotor aerodynamic model based on continuous finite vortex theory to predict rotor thrust within gas–liquid flow field.Initially,the model's sensitivity to system parameters was analyzed to optimize its predictive capabilities.Subsequently,a comprehensive ground/water experimental setup was designed to investigate the intricate aerodynamic interactions between the rotor flow field and water.By varying rotor sizes,the characteristics of the rotor flow field and water surface were examined at different rotor-water surface distances.The performance of different modeling methods was analyzed based on the rotor experimental data of a diameter of 0.38 m,and the prediction results were quantified using the percentage of the mean-square error.The results show that the average error of the finite vortex rotor model is the smallest.Finally,a novel transition boundary is proposed to divide the rotor flow field of the gas–liquid mixture into two stages.The thrust loss zone is defined to delineate the safe operating range of the aircraft,providing a basis for the design of aerial-aquatic rotorcraft.展开更多
The drivetrain system of tiltrotor aircraft is a complicated multibody system.Traditionally,rotorcraft drivetrain systems are modeled by the finite element method using an equivalent mathematical model with all the el...The drivetrain system of tiltrotor aircraft is a complicated multibody system.Traditionally,rotorcraft drivetrain systems are modeled by the finite element method using an equivalent mathematical model with all the elements spinning at the same rotational velocity and structural properties scaled according to gear ratios.Such a process can be complex and computationally expensive,especially for large-scale problems.This paper proposes the dynamic analysis of a tiltrotor drivetrain,coupled with flexible blades'lagwise motion,using a novel multibody system modeling and analysis method based on the transfer matrix method.The proposed method eliminates the need for equivalent processing of the drivetrain system components and does not require the derivation of the overall governing equations based on the Hamilton principle.Instead,they are directly formulated according to the system's topology graph.Virtual branch and geometric elements are introduced to decouple any topological structure of the drivetrain system into multiple independent chain systems,further reducing the modeling complexity.展开更多
A generalized solution scheme using implicit time integrators for piecewise linear and nonlinear systems is developed.The piecewise linear characteristic has been well‐discussed in previous studies,in which the origi...A generalized solution scheme using implicit time integrators for piecewise linear and nonlinear systems is developed.The piecewise linear characteristic has been well‐discussed in previous studies,in which the original problem has been transformed into linear complementarity problems(LCPs)and then solved via the Lemke algorithm for each time step.The proposed scheme,instead,uses the projection function to describe the discontinuity in the dynamics equations,and solves for each step the nonlinear equations obtained from the implicit integrator by the semismooth Newton iteration.Compared with the LCP‐based scheme,the new scheme offers a more general choice by allowing other nonlinearities in the governing equations.To assess its performances,several illustrative examples are solved.The numerical solutions demonstrate that the new scheme can not only predict satisfactory results for piecewise nonlinear systems,but also exhibits substantial efficiency advantages over the LCP‐based scheme when applied to piecewise linear systems.展开更多
基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.KYCX24_0532)the Key Laboratory of Cross-Domain Flight Interdisciplinary Technology,China(Nos.2024-KF03001,2024-KF03003)the National Natural Science Foundation of China(No.12272169)for the financial support。
文摘Blending the agility of aerial drones with the covert capabilities of underwater submersibles,the aerial-aquatic rotorcraft has garnered substantial interest due to their unparalleled capacity to traverse both air and water.Nevertheless,a critical hurdle for these vehicles lies in mitigating the adverse effects of repeatedly transitioning between these environments,particularly during water-surface takeoffs.Currently,research on the interference caused by rotors approaching water surfaces remains limited.This paper introduces a novel adaptive rotor aerodynamic model based on continuous finite vortex theory to predict rotor thrust within gas–liquid flow field.Initially,the model's sensitivity to system parameters was analyzed to optimize its predictive capabilities.Subsequently,a comprehensive ground/water experimental setup was designed to investigate the intricate aerodynamic interactions between the rotor flow field and water.By varying rotor sizes,the characteristics of the rotor flow field and water surface were examined at different rotor-water surface distances.The performance of different modeling methods was analyzed based on the rotor experimental data of a diameter of 0.38 m,and the prediction results were quantified using the percentage of the mean-square error.The results show that the average error of the finite vortex rotor model is the smallest.Finally,a novel transition boundary is proposed to divide the rotor flow field of the gas–liquid mixture into two stages.The thrust loss zone is defined to delineate the safe operating range of the aircraft,providing a basis for the design of aerial-aquatic rotorcraft.
基金the National Natural Science Foundation of China(No.12272169)the Project of Key Laboratory of Cross-Domain Flight Interdisciplinary Technology,China(Nos.2024-KF03001 and 2024-KF03003)Technology Development Project,China(No.XYZX040401)for the financial support。
文摘The drivetrain system of tiltrotor aircraft is a complicated multibody system.Traditionally,rotorcraft drivetrain systems are modeled by the finite element method using an equivalent mathematical model with all the elements spinning at the same rotational velocity and structural properties scaled according to gear ratios.Such a process can be complex and computationally expensive,especially for large-scale problems.This paper proposes the dynamic analysis of a tiltrotor drivetrain,coupled with flexible blades'lagwise motion,using a novel multibody system modeling and analysis method based on the transfer matrix method.The proposed method eliminates the need for equivalent processing of the drivetrain system components and does not require the derivation of the overall governing equations based on the Hamilton principle.Instead,they are directly formulated according to the system's topology graph.Virtual branch and geometric elements are introduced to decouple any topological structure of the drivetrain system into multiple independent chain systems,further reducing the modeling complexity.
文摘A generalized solution scheme using implicit time integrators for piecewise linear and nonlinear systems is developed.The piecewise linear characteristic has been well‐discussed in previous studies,in which the original problem has been transformed into linear complementarity problems(LCPs)and then solved via the Lemke algorithm for each time step.The proposed scheme,instead,uses the projection function to describe the discontinuity in the dynamics equations,and solves for each step the nonlinear equations obtained from the implicit integrator by the semismooth Newton iteration.Compared with the LCP‐based scheme,the new scheme offers a more general choice by allowing other nonlinearities in the governing equations.To assess its performances,several illustrative examples are solved.The numerical solutions demonstrate that the new scheme can not only predict satisfactory results for piecewise nonlinear systems,but also exhibits substantial efficiency advantages over the LCP‐based scheme when applied to piecewise linear systems.
