Recent rotor wake simulation and modeling studies at United Technologies Corporation

Egolf, T. Alan; Wake, Brian; Berezin, Charles R.

doi:10.2514/6.2000-115

Cited by 18 publications

(13 citation statements)

References 7 publications

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“…In comparison with alternative approaches (e.g., the local refinement of the Cartesian background grid), vortexadapted grids have the advantage to be topologically well adapted to the tip vortices. The method of vortex-tracking Chimera grids has been previously used by, amongst others, Egolf et al [2], Hariharan [27], and Lee and Baeder [28]. The strategy presented in this work is comparable, but the method is directly applied to a trimmed rotor in BVI flight condition.…”

Section: Vortex-tracking Methodologymentioning

confidence: 93%

“…In hover, for instance, at least eight revolutions of the tip vortex have to be included in a numerical simulation to correctly compute the influence of the vortex-induced velocities on the blades and thus to predict the aerodynamics of the rotor correctly [1]. For a slowdescent flight with a low advance ratio, the correct reproduction and conservation of the tip vortices is mandatory to correctly capture blade-vortex interaction (BVI) effects and thus to provide an accurate database for acoustic postprocessing [2]. The effort that is necessary to correctly reproduce the vortex system differs for the different computational methods that can be applied for the analysis.…”

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confidence: 99%

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Tip Vortex Conservation on a Helicopter Main Rotor Using Vortex-Adapted Chimera Grids

et al. 2007

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This paper presents a method to improve the tip vortex conservation in a computational fluid dynamics simulation of a helicopter main rotor. Our approach uses vortex-adapted Chimera child grids to achieve a local refinement of the grid in the vicinity of the vortex and thus reduce the numerical dissipation of the vortex. The method is applied to the higher-harmonic-control aeroacoustic rotor test case to evaluate its potential with respect to the prediction of bladevortex interaction airloads. To allow a meaningful comparison with the experimental data, the rotor is trimmed for thrust, as well as for longitudinal and lateral mast moments, using weak fluid-structure coupling with a flight mechanics code. We obtained a good overall agreement with the experimental data for both aerodynamics and blade dynamics. The effect of the improvement in tip vortex conservation is demonstrated by comparison with simulations without Chimera refinement and with the experimental results. It turned out that a very fine grid resolution in the vicinity of the vortex is necessary to capture the blade-vortex interaction airloads. The required grid resolution was provided by a refinement of the vortex-adapted grids, allowing for a very good reproduction of the blade-vortex interaction airloads, especially on the retreating blade side. Nomenclature C m Ma 2 = sectional pitching moment coefficient C n Ma 2 = sectional normal force coefficient F z = rotor thrust, N Ma tip = hover tip Mach number M x = rotor mast rolling moment, Nm M y = rotor mast pitching moment, Nm q = rotor shaft angle, deg c = longitudinal cyclic pitch angle, deg s = lateral cyclic pitch angle, deg 0 = collective pitch angle, deg 3=rev = three-per-revolution higher-harmonic-control amplitude, deg = advance ratio = rotor azimuth angle, deg w = wake age, deg 3=rev = three-per-revolution pitch control phase, deg

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Section: Vortex-tracking Methodologymentioning

confidence: 93%

mentioning

confidence: 99%

Tip Vortex Conservation on a Helicopter Main Rotor Using Vortex-Adapted Chimera Grids

et al. 2007

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“…However, traditional low-order spatially accurate computational methodologies tend to dissipate the vortex wake due to the excessive numerical dissipation inbuilt in such numerical schemes, which leads to the tip vortex to be captured with much less intensity than the physical reality [1][2][3][4] . Thus, one of the central issues facing the future of the first principles by using the Navier-Stokes simulation for rotor wakes is their ability to capture the vorticity with the minimal numerical dissipation [4][5][6] .…”

Section: Introductionmentioning

confidence: 98%

Rotor wake capture improvement based on high-order spatially accurate schemes and chimera grids

Weng

2011

Appl. Math. Mech.-Engl. Ed.

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A high-order upwind scheme has been developed to capture the vortex wake of a helicopter rotor in the hover based on chimera grids. In this paper, an improved fifth-order weighted essentially non-oscillatory (WENO) scheme is adopted to interpolate the higher-order left and right states across a cell interface with the Roe Riemann solver updating inviscid flux, and is compared with the monotone upwind scheme for scalar conservation laws (MUSCL). For profitably capturing the wake and enforcing the period boundary condition, the computation regions of flows are discretized by using the structured chimera grids composed of a fine rotor grid and a cylindrical background grid. In the background grid, the mesh cells located in the wake regions are refined after the solution reaches the approximate convergence. Considering the interpolation characteristic of the WENO scheme, three layers of the hole boundary and the interpolation boundary are searched. The performance of the schemes is investigated in a transonic flow and a subsonic flow around the hovering rotor. The results reveal that the present approach has great capabilities in capturing the vortex wake with high resolution, and the WENO scheme has much lower numerical dissipation in comparison with the MUSCL scheme.

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“…Results for a hovering rotor with tip vortex tracking grids using OVERFLOW have been presented by Egolf et. al 14 . Strawn et al 15 have systematically studied the effects of grid refinement on the hover performance prediction characteristics of rotors.…”

Section: Introductionmentioning

confidence: 98%

Application of a Symmetric Total Variation Diminishing scheme to shock noise of rotors

Usta

Wang

Sankar

2000

38th Aerospace Sciences Meeting and Exhibit

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A Symmetric Total Variation Diminishing (STVD) scheme is applied to model the aeroacoustic and aerodynamics characteristics of rotors in hover. A modified version of the finite volume code TURNS (Transonic Unsteady Rotor Navier-Stokes) is used. The original TURNS solver uses a third order upwind scheme. The modified solver, referred to as TURNS-STVDx, is fourth, sixth, or eighth order accurate in space, and first or second order accurate in time. Calculations are presented for the high-speed impulsive noise emanating from a non-lifting UH-1H rotor, and the performance of the UH-60A rotor in hover. Encouraging improvements over the baseline method have been obtained. The modified method was not, however, able to model the tip vortex more accurately than the baseline solver. This is attributable to the numerical viscosity term that has the same form in the present solver and the baseline solver. Additional work is needed to improve the modeling of the tip vortex structure in the present methodology. In particular, higher order essentially nonoscillatory schemes (ENO) may be needed in the vicinity of the tip vortices.

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Recent rotor wake simulation and modeling studies at United Technologies Corporation

Cited by 18 publications

References 7 publications

Tip Vortex Conservation on a Helicopter Main Rotor Using Vortex-Adapted Chimera Grids

Tip Vortex Conservation on a Helicopter Main Rotor Using Vortex-Adapted Chimera Grids

Rotor wake capture improvement based on high-order spatially accurate schemes and chimera grids

Application of a Symmetric Total Variation Diminishing scheme to shock noise of rotors

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