Computational and Experimental Investigations of Coaxial Rotor Unsteady Loads

Singh, Rajneesh; Kang, Hao; Cameron, Christopher G.; Sirohi, Jayant

doi:10.2514/6.2016-1787

Cited by 17 publications

(9 citation statements)

References 3 publications

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“…The other prediction result, which was computed by Singh et al using Helios, 41) is also indicated in The trim and CSD analysis were computed using the comprehensive analysis code RCAS. The details of the CFD method are not shown in Singh et al 41) The predicted results of rFlow3D are in excellent agreement with the experimental data and Singh's results. Therefore, the implemented trim analysis method can satisfactorily predict the aerodynamic performance of the coaxial rotor system when hovering.…”

Section: Computational Results Of Aerodynamic Perform-mentioning

confidence: 99%

“…Similarly, several comprehensive analysis tools were validated by Lim et al, 19) Ho et al, 20) and Schmaus et al 21,22) The static aerodynamic performance of the coaxial rotor using comprehensive analysis was well predicted when compared to the experimental data. Furthermore, validations of the computational fluid dynamics (CFD) tools were conducted by Lakshminarayan et al, 23) Singh et al, 24) and Yoon et al 25) The ability of CFD to predict the static hovering performance of the coaxial rotor system was indicated.…”

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confidence: 99%

“…Several CFD tools can be combined with comprehensive analysis tools to attain the trim condition of the coaxial rotor system. 24,26,27) It is difficult for the other CFD tools to carry out an analysis of the coaxial rotor system because the specific published or developed comprehensive code is required. Therefore, the trim analysis method for the coaxial rotor system is desired to be considered within the CFD tool.…”

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confidence: 99%

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A Coupled CFD/Trim Analysis of Coaxial Rotors

Sugawara

Tanabe

Kameda

2022

Trans. Japan Soc. Aero. S Sci.

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A numerical simulation method of computational fluid dynamics (CFD) coupling with a trim analysis for coaxial rotor systems is described in this paper. The trim analysis is implemented using a rotorcraft flow solver, rFlow3D. Six target forces and moments, which are the thrust of the coaxial rotor system, the rolling and pitching moments for each upper and lower rotor, and the torque balance for yaw control, are considered as the trim conditions. The blade pitch angles of both upper and lower rotors are adjusted to satisfy the target trim conditions through the trim analysis by being loosely coupled with the CFD solver. Verification of the trim analysis method and validation of the prediction accuracy of aerodynamic performance are performed based on previous experimental and numerical studies in hover and forward flight using the lift-offset conditions. It is shown that the predicted hover performances of the torque-balanced coaxial rotors are in excellent agreement with the experimental data. It is also verified that the lift-offset conditions in forward flight are simulated using this established trim analysis. Furthermore, reasonable agreements with other computational results are indicated.

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Section: Computational Results Of Aerodynamic Perform-mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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A Coupled CFD/Trim Analysis of Coaxial Rotors

Sugawara

Tanabe

Kameda

2022

Trans. Japan Soc. Aero. S Sci.

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“…Numerical simulations, including computationally efficient vortex-lattice methods and high-fidelity Computational Fluid Dynamics (CFD) simulations, have greatly contributed to the advancement of the aeromechanics of coaxial rotors. Past CFD studies aimed to obtain a deep understanding of the unsteady aerodynamic loads of rotors, and were often coupled with Computational Structural Dynamics (CSD) to understand the vibratory loads and affect rotor design parameters, such as rotor spacing, stiffness, lift offset, and clocking (4,6) . However, the unsteady aerodynamic predictions of a coaxial rotor by CFD are affected by several factors such as the need for high-density grids to capture the rotor wake, and the associated computational cost in finding just one solution is considerable.…”

Section: Introductionmentioning

confidence: 99%

Unsteady loads for coaxial rotors in forward flight computed using a vortex particle method

2018

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Recent advances in coaxial rotor design have shown benefits of this configuration. Nevertheless, issues related to rotor-head drag, aerodynamic performance, wake interference, and vibration should also be considered. Simulating the unsteady aerodynamic loads for a coaxial rotor, including the aerodynamic interactions between rotors and rotor blades, is an essential part of analysing their vibration characteristics. In this article, an unsteady aerodynamic analysis based on a vortex particle method is presented. In this method, a reversed-flow model for the retreating side of the coaxial rotor is proposed based on an unsteady panel technique. To account for reversed flow, shedding a vortex from the leading edge is used rather than from the trailing edge. Moreover, vortex-blade aerodynamic interactions are accounted for. The model considers the unsteady pressure term induced on a blade by tip vortices of other blades, and thus accounts for the aerodynamic interaction between the rotors and its contribution to the unsteady airloads. Coupling the reversed-flow model and the vortex-blade aerodynamic interaction model with the viscous vortex-particle method is used to simulate the complex wake of the coaxial rotor. The unsteady aerodynamic loads on the X2 coaxial rotor are simulated in forward flight, and compared with the results of PRASADUM (Parallelized Rotorcraft Analysis for Simulation And Design, developed at the University of Maryland) and CFD/CSD computations with the OVERFLOW and the CREATE-AV Helios tools. The results of the present method agree with the results of the CFD/CSD method, and compare to it better than the PRASADUM solutions. Furthermore, the influence of the aerodynamic interaction between the coaxial rotors on the unsteady airloads, frequency, wake structure, induced flow, and force distributions are analysed. Additionally, the results are also compared against computations for a single-rotor case, simulated at similar conditions as the coaxial rotor. It is shown that the effect of tip vortex interaction plays a significant role in unsteady airloads of coaxial rotors at low speeds, while the rotor blade passing effect is obviously strengthened at high-speed.

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“…Lakshminarayan and Baeder [15] used compressible RANS solver with sliding mesh interpolation scheme to predict instantaneous thrust and power influenced by the interaction between coaxial rotors. Singh et al [16] used lowand high-fidelity with loose coupling method to computational simulated steady and unsteady performance of elastic coaxial rotor with vibratory hubloads.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamics Optimization of a Ducted Coaxial Rotor in Forward Flight Using Orthogonal Test Design

Jiang

Jia

2018

Shock and Vibration

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To investigate the aerodynamic complexities involved in the combination of freestream and propeller’s suction flow field of ducted coaxial rotors system in forward flight, an orthogonal L16(43) test design has been applied to optimize the design parameters including forward speed, pitch angle, and axial spacing between rotors. Multiblock grids and Multiple Frame of Reference (MFR) method are adopted for calculating aerodynamic performance of the system, hover characteristic was compared with experimental data obtained from the test stand, and the thrust performance is well predicted for various rotor spacing and a range of rpm. This solution approach is developed for the analytical prediction of forward flight and the simulation results indicated that the design parameters influenced lift, drag, and torque reduced in the order: wind speed > rotor spacing > pitch angle, wind speed > pitch angle, and rotor spacing > wind speed > pitch angle, respectively. The optimal rotor spacing and pitch angle were determined to maximize the aerodynamic performance considering high lift, low drag, and trimmed torque.

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Computational and Experimental Investigations of Coaxial Rotor Unsteady Loads

Cited by 17 publications

References 3 publications

A Coupled CFD/Trim Analysis of Coaxial Rotors

A Coupled CFD/Trim Analysis of Coaxial Rotors

Unsteady loads for coaxial rotors in forward flight computed using a vortex particle method

Aerodynamics Optimization of a Ducted Coaxial Rotor in Forward Flight Using Orthogonal Test Design

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