Time Spectral Method for Rotorcraft Flow

Butsuntorn, Nawee; Jameson, Antony

doi:10.2514/6.2008-403

Cited by 14 publications

(5 citation statements)

References 38 publications

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“…In the work performed by Steinhoff et al mainly the incompressible fluid equations are considered, although a few applications also concern compressible flows. The technique has also been used by a number of researchers (Dadone et al, 2001;Butsuntorn and Jameson, 2008), allowing for example to simulate 2D vortex-airfoil interactions (Morvant et al, 2005). In spite of its success in producing spectacular results, the method is still controversial, the idea of modifying the Euler/Navier-Stokes equations being not well accepted.…”

Section: Introductionmentioning

confidence: 98%

Application of vorticity confinement to rotor wake simulations

Costes

Renaud

Rodriguez

et al. 2012

IJESMS

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The VC2 vorticity confinement technique introduced by Steinhoff for vortex dominated flows is presented. After a brief description of the formulation and of its theoretical developments, the method is applied to the simulation of helicopter rotor wakes, focusing on two configurations: the rotor in hover, for which the flow field is mainly driven by the wake characteristics, and the rotor in low-speed descent flight where BVI noise is created. The results obtained show the efficiency of the approach, which provides wake predictions of the same or even better quality as higher-order methods.

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Section: Introductionmentioning

confidence: 98%

Application of vorticity confinement to rotor wake simulations

Costes

Renaud

Rodriguez

et al. 2012

IJESMS

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“…Therefore, the effect of nonlinear harmonic coupling would not be considered. On the other hand, in the nonlinear harmonic method, known as Harmonic Balance , 13,15,16 Non-Linear Frequency Domain (NLFD), 29,30,34,35 and Time Spectral, 5,6,11,12,26,27,44,53 all the harmonic equations are solved coupled. Besides, there is no restriction on the amplitude of the perturbation terms.…”

Section: Introductionmentioning

confidence: 99%

Algorithmic Advanced for the Adaptive Non-Linear Frequency Domain Method.

Mohamadi

Nadarajah

2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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An innovative implicit approach for the adaptive Nonlinear Frequency Domain method (adaptive NLFD) has been introduced for the Navier-Stokes equations on deformable grids. It has been shown that for a periodic flow problem, a huge reduction in the computational costs and a spectral temporal accuracy of the results could be achieved by solving the flow governing equations in the frequency instead of the time domain. This computational efficiency may be even further enhanced through an adaptive modal augmentation of the Fourier series representing the local flow solution. In the present study, to accelerate the convergence rate, an innovative modified nonlinear LU-SGS technique is proposed, where the modes are updated in a segregate fashion. The unique and important outcome of this implementation is that the computational efficiency of the solver does not decrease as the number of modes increases. Results are presented for the laminar vortex shedding behind a stationary cylinder, a stationary transonic airfoil, and a plunging airfoil and are compared with previous numerical results as well as experimental data.

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“…Robinson [29] proposed a scaling expression based on helicity by extending Lohner's work. Butsuntorn and Jameson [30] further extended the helicity formulation of Robinson by including a non-dimensional scaling parameter based on the local mesh size. In most studies, the ε value comes from a trial-and-error procedure, which is less efficient.…”

Section: Introductionmentioning

confidence: 99%

Assessment of the Vortex Feature-Based Vorticity Confinement Method Applied to Rotor Aerodynamics and Aeroacoustics

Vigevano

2023

Aerospace

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The accurate prediction of helicopter rotor aerodynamics and aeroacoustics using Computational Fluid Dynamics (CFD) techniques still remains a challenge, as the over-dissipation of numerical schemes results in a higher diffusive rate of rotor wake and vortices than what can be expected from the fluid governing equations. To alleviate this issue, a vortex feature-based vorticity confinement (FVC2-L2) method that combines the locally normalized λ2 vortex detection method with the standard second vorticity confinement (VC2) scheme is presented to counterbalance the truncation error introduced by the numerical discretization of the convective term while avoiding the over-confinement inside the boundary layer. The FVC2-L2 scheme is adopted for helicopter rotor aerodynamic and aeroacoustic predictions through its implementation in the multi-block structured grid CFD solver ROSITA and coupling with the aeroacoustic code ROCAAP based on the permeable surface Ffowcs Williams–Hawkings (PS-FWH) equation. This approach is assessed in helicopter rotor flows via three databases. Firstly, the well-documented HART-II rotor in the baseline condition is used to evaluate the capability of the presented VC scheme in blade–vortex interaction (BVI) phenomena prediction. Subsequently, the UH-1H non-lifting hovering rotor and the AH-1/OLS low-speed descending flight rotor are adopted for assessment of such a method in aeroacoustics. The benefits of the FVC2-L2 scheme in terms of aerodynamics prediction, wake preservation, and noise signal prediction are well demonstrated by comparison with the experimental data and the results obtained without VC schemes. Particularly, the FVC2-L2 scheme mainly improves the highly unsteady airloads prediction, and results in an improvement of BVI noise prediction by more than 5 dB with respect to the case without VC schemes for AH-1/OLS rotor case. Additionally, some shortcomings of the approach are noticed in engineering applications. On the basis of a simplified convective vortex, some provisional guidelines on the required εo value in terms of number of cells per vortex diameter are provided: an εo value ranging from 0.01 to 0.04 for grids which may represent the vortex core diameter with 6 to 12 cells.

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Time Spectral Method for Rotorcraft Flow

Cited by 14 publications

References 38 publications

Application of vorticity confinement to rotor wake simulations

Application of vorticity confinement to rotor wake simulations

Algorithmic Advanced for the Adaptive Non-Linear Frequency Domain Method.

Assessment of the Vortex Feature-Based Vorticity Confinement Method Applied to Rotor Aerodynamics and Aeroacoustics

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