Development of a Simulation and Optimization Framework for Improved Aerodynamic Performance of R/C Helicopter Rotor Blades

Wiebe, Jonathan

doi:10.22215/etd/2015-10913

Cited by 4 publications

(3 citation statements)

References 14 publications

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“…Finally, we believe that a proper extension of the present theory to the anisotropic XXZ case would allow one to investigate the unusual magnetic features of the recently found [46,47,48] inorganic spin-1/2 triangular antiferromagnets, Ba 3 CoSb 2 O 9 and Ba 3 CuSb 2 O 9 . An experimental realization of the related XY model has been proposed recently in the area of ultra-cold atoms in optical lattice potentials [49,50].…”

Section: Discussionmentioning

confidence: 84%

Low temperature properties of the triangular-lattice antiferromagnet: a bosonic spinon theory

et al. 2012

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We study the low temperature properties of the triangular-lattice Heisenberg antiferromagnet with a mean field Schwinger spin-1 2 boson scheme that reproduces quantitatively the zero temperature energy spectrum derived previously using series expansions. By analyzing the spin-spin and the boson density-density dynamical structure factors, we identify the unphysical spin excitations that come from the relaxation of the local constraint on bosons. This allows us to reconstruct a free energy based on the physical excitations only, whose predictions for entropy and uniform susceptibility seem to be reliable within the temperature range 0 T 0.3J , which is difficult to access by other methods. The high values of entropy, also found in high temperature expansion studies, can be attributed to the roton-like narrowed dispersion at finite temperatures. of several numerical techniques [3][4][5][6][7][8][9][10][11] was crucial to elucidate that the zero point quantum fluctuations in this particular system are not enough to destroy the classical 120 • Néel order, lending support to a simple semiclassical description at low temperatures such as that provided by linear spin wave theory (LSWT) [12].Nonetheless, early high temperature expansion (HTE) studies [6] performed down to low temperatures showed no evidence of a renormalized classical behavior as predicted by the nonlinear sigma model (NLσ M) [13,14]. For instance, around T = 0.25J , the correlation length calculated by HTE is only ξ ∼ 1.5 lattice constants, in contrast to the value ξ ∼ 12 predicted by NLσ M [6,10]. Consistent with these values, the entropy calculated by HTE was one order of magnitude larger than that of the NLσ M. These early results were interpreted as a probable crossover between renormalized classical and quantum critical regimes [15].Unexpectedly, series expansion (SE) studies [10,16] performed at zero temperature also showed a strong downward renormalization of the high energy part of the spectrum with respect to LSWT, along with the appearance of roton-like minima at the midpoints of the edges of the hexagonal Brillouin zone (BZ). Originally, the presence of such roton-like excitations were proposed to be related to possible fermionic spinon excitations which in turn would lead to the anomalous low temperature properties of the THM [10]. However, subsequent works showed that nontrivial 1/S corrections, arising from the noncollinearity of the 120 • Néel order, accurately recovers the T = 0 SE results [17][18][19]. This gave support to an interacting magnon picture for the spectrum, although it was found that the magnon-quasiparticles are not well defined for a significant part of the BZ [18,19]. Nevertheless, by assuming a bosonic character for the SE dispersion relation, the high values of entropy found at low temperature was attributed to the thermal excitation of rotons, even at temperatures below the roton gap [10].Here we explore the low temperature properties of THM from an alternative viewpoint: a bosonic spinon perspective, based on the Sch...

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Section: Discussionmentioning

confidence: 84%

Low temperature properties of the triangular-lattice antiferromagnet: a bosonic spinon theory

et al. 2012

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“…It was necessary to increase the root pitch angle of the blades by 1 degree to match power coefficients. De Gennaro [44] also found this increase to be necessary and further simulations using a custom Blade Element Momentum Theory (BEMT) code [56] and the commercial CFD software StarCCM+ also reached the same conclusion. It is suspected that the original data by Dittmar [9] may have an error in the reported root pitch angle.…”

Section: Aerodynamic Validationmentioning

confidence: 72%

Numerical Predictions of Propeller-Wing Interaction Induced Noise in Cruise and Off-Design Conditions

Boots¹

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Using numerical methods, the aeroacoustic field induced by the interaction of a 4-bladed NASA SR-2 propeller and its wake with a wing is investigated under cruise conditions (Mach 0.6). The SmartRotor code, a coupled vortex particle and panel method, which is integrated with an acoustic solver based on the Farassat 1A formulation of the Ffowcs-Williams Hawkings equation, was used. Three main areas were investigated: the effect of propeller tip geometry on the propeller's wake and blade tip vortex; the effect of integrating a wing in the tractor configuration, including the effect of its position, and wing local leading edge sweep; and the effect of operating the combined wing/propeller system in off-design conditions such as low forward speed or in non-axial inflow.It was discovered that tip sweep is effective at reducing propeller tip vortex strength with no adverse effect on noise. Modifying tip dihedral was found to always increase tip vortex strength. Integrating a wing in the wake of the propeller increased the broadband noise generated, but had little effect on harmonic noise. The downstream position of the wing was found to not affect noise while vertical offset from the propeller axis increased noise. The most important discovery was that applying local leading edge sweep to the wing in the region of the propeller's wake decreases noise proportionally to the change in the angle between the helical tip vortex and the wing's leading edge. These noise reductions were on the order of up to 1.3 dB for overall sound pressure level, and 7.5 dB at the blade passage frequency.iii Acknowledgements First on the list of many people to thank must be my supervisor, Professor Daniel Feszty. His constant enthusiasm and support of my work was invaluable whenever simulations weren't working or results seemed less than reasonable. At the same time, his way of providing guidance while allowing me to choose the direction of my research allowed me to follow up on interesting results and truly take ownership of this work. For this and so much more, thank you.

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“…However, because the thrust and power coefficients are relatively small, the thrust and torque variations do not translate into large discrepancy in acoustic predictions. A simple blade element theory calculation, based on the QOPTR code from Jonathan Wiebe[125] yielded thrust results of 61.4 N, more in…”

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confidence: 99%

Computational Aeroacoustic Prediction of Propeller Noise Using Grid-Based and Grid-Free CFD Methods

Hambrey¹

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Two CFD codes are used to simulate noise data for a tandem cylinder experiment and two scaled NASA SR-2 propeller tests. The first code, STAR CCM+, is a grid-based commercial CFD code while the second code, SmartRotor, is an in-house grid-free CFD code which uses a panel method coupled with a discrete vortex method. Good comparison to experiment is achieved, with STAR CCM+ predicting the vortex shedding of the tandem cylinder case within 3 Hz and 10 dB while also predicting first propeller harmonics within 20 and 11 dB for the first and second propeller simulations, respectively. SmartRotor predicted first propeller harmonics within 6 and 37 dB for the first and second experiments, respectively. A parametic study on the influence of blade count on propeller noise was then performed using both codes to simulating the noise of 7-, 8-, and 10-bladed propellers finding quieter operation with increasing blade count.

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Development of a Simulation and Optimization Framework for Improved Aerodynamic Performance of R/C Helicopter Rotor Blades

Cited by 4 publications

References 14 publications

Low temperature properties of the triangular-lattice antiferromagnet: a bosonic spinon theory

Low temperature properties of the triangular-lattice antiferromagnet: a bosonic spinon theory

Numerical Predictions of Propeller-Wing Interaction Induced Noise in Cruise and Off-Design Conditions

Computational Aeroacoustic Prediction of Propeller Noise Using Grid-Based and Grid-Free CFD Methods

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