Analysis methodology for 3C-PIV data of rotary wing vortices

Wall, Berend G. van der; Richard, Hugues

doi:10.1007/s00348-006-0117-x

Cited by 83 publications

(47 citation statements)

References 9 publications

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“…The largest measurement error in the velocity domain and the relative measurement errors for all the test cases, for the displacement error of e x = 0.1 px are reported in Table 1. The PIV spatial resolution is characterised by the measurement volume length L m , and previous works (Martin et al 2000;van der Wall and Richard 2006) have shown that the correct measurement of the vortex characteristics is obtained for L m /r c B 0.2, where r c is the vortex core radius defined as the radial distance from the vortex centre where the maximum tangential velocity is reached (Fig. 5).…”

Section: Accuracy Estimationmentioning

confidence: 99%

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A comprehensive PIV measurement campaign on a fully equipped helicopter model

2011

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The flow field around a helicopter is characterised by its inherent complexity including effects of fluidstructure interference, shock-boundary layer interaction, and dynamic stall. Since the advancement of computational fluid dynamics and computing capabilities has led to an increasing demand for experimental validation data, a comprehensive wind tunnel test campaign of a fully equipped and motorised generic medium transport helicopter was conducted in the framework of the GOAHEAD project. Different model configurations (with or without main/tail rotor blades) and several flight conditions were investigated. In this paper, the results of the three-component velocity field measurements around the model are surveyed. The effect of the interaction between the main rotor wake and the fuselage for cruise/tail shake flight conditions was analysed based on the flow characteristics downstream from the rotor hub and the rear fuselage hatch. The results indicated a sensible increment of the intensity of the vortex shedding from the lower part of the fuselage and a strong interaction between the blade vortex filaments and the wakes shed by the rotor hub and by the engine exhaust areas. The pitch-up phenomenon was addressed, detecting the blade tip vortices impacting on the horizontal tail plane. For high-speed forward flight, the shock wave formation on the advancing blade was detected, measuring the location on the blade chord and the intensity. Furthermore, dynamic stall on the retreating main rotor blade in high-speed forward flight was observed at r/R = 0.5 and 0.6. The analysis of the substructures forming the dynamic stall vortex revealed an unexpected spatial concentration suggesting a rotational stabilisation of large-scale structures on the blade. Abbreviations CFDComputational fluid mechanics DEHS Di-ethyl-hexyl-sebacat DS Dynamic stall GOAHEAD Generation of advanced helicopter experimental aerodynamic database for CFD code validation PIV Particle image velocimetry WT Wind tunnel Symbols a Speed of sound, m/s c Blade chord, m L Fuselage length, m L m Measurement volume length, m M Mach number r Radial coordinate, m r v Vortex radius, m r c Vortex core radius, m R Rotor radius, m t Time, s

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Section: Accuracy Estimationmentioning

confidence: 99%

“…Heineck et al 2000;Martin et al 2001;Lee et al 2008) or low-speed forward flight (e.g. Raffel et al 1998;Le Pape et al 2007;Van der Wall and Richard 2006). Today, cutting edge computational fluid mechanics (CFD) tools are capable of predicting the viscous flow around rotor-fuselage configurations advancing towards complete helicopters.…”

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confidence: 97%

A comprehensive PIV measurement campaign on a fully equipped helicopter model

2011

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“…It is observed that the fuselage leads to a larger high-frequency content of the blade motion that might impact BVI oscillations. Next, predicted vortex wake positions are correlated with those obtained from the DNW particle-image-velocimetry measurement images [21]. The selected locations lie in the longitudinal cutting planes at y h 1.4 m (denoted as P17 to P23) and at −1.4 m (denoted as P43 to P47) when the reference blade is positioned at azimuth angles of 70 or 20 deg [2].…”

Section: B Correlation Of Airloads Blade Motions and Vortex Trajecmentioning

confidence: 99%

Loose Fluid-Structure Coupled Approach for a Rotor in Descent Incorporating Fuselage Effects

Jung

Hwan

You

et al. 2013

Journal of Aircraft

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A loose coupling approach is used to combine a comprehensive structural dynamics code CAMRAD II and a computational fluid dynamics solver KFLOW to validate the data and to identify the effect of fuselage on the aeroelastic behavior of the second higher harmonic rotor acoustic test rotor. The computations are made using isolated rotor and rotor-fuselage models. To demonstrate the effect of a fuselage, the shaft tilt angles remain identical for both configurations. A good correlation has been obtained with the present computational fluid dynamics/ comprehensive structural dynamics method. It is observed that a rotor-fuselage model improves the correlation significantly in terms of magnitudes and phases of the airloads solution. All the blade-vortex interaction peaks are captured accurately, and the phase shift in the section normal forces improves significantly, with the inclusion of a fuselage. The sources of improvements are investigated, considering the vorticity distributions and induced velocity fields of a rotor. It is revealed that the upwash pattern due to a fuselage is not restricted locally but propagates to considerable portions of the disk. Numerical results indicate that the upwash is responsible to lift up vortices at the zone of interest for a reduced miss distance, which results in a stronger blade-vortex interaction for improved correlations. Nomenclature= hub-based Cartesian coordinates α s = shaft tilt angle θ 0 , θ 1c , θ 1s = control pitch angles μ = advance ratio σ = solidity ψ = rotor azimuth angle Ω = rotor rotational speed

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“…A 3C-PIV technique [25] was used in the HART II test program to give instantaneous measurements of the velocity field contained within a series of highly resolved observation areas near to the rotor. These observation areas were located along five longitudinal slices through the flow between Y=R 0:4 and Y=R 0:97, as indicated in Fig.…”

Section: Trajectory Of Tip Vorticesmentioning

confidence: 99%

Influence of Blade Aerodynamic Model on the Prediction of Helicopter High-Frequency Airloads

Kelly

Brown²

2011

Journal of Aircraft

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Brown's vorticity transport model has been used to investigate the influence of the blade aerodynamic model on the accuracy with which the high-frequency airloads associated with helicopter blade-vortex interactions can be predicted. The model yields an accurate representation of the wake structure yet allows significant flexibility in the way that the blade loading can be represented. A simple lifting-line model and a somewhat more sophisticated liftingchord model, based on unsteady thin aerofoil theory, are compared. A marked improvement in the accuracy of the predicted high-frequency airloads of the higher harmonic control aeroacoustic rotor is obtained when the liftingchord model is used instead of the lifting-line approach, and the quality of the prediction is affected less by the computational resolution of the wake. The lifting-line model overpredicts the amplitude of the lift response to bladevortex interactions as the computational grid is refined, exposing the fundamental deficiencies in this approach when modeling the aerodynamic response of the blade to interactions with vortices that are much smaller than its chord. The airloads that are predicted using the lifting-chord model are relatively insensitive to the resolution of the computation, and there are fundamental reasons to believe that properly converged numerical solutions may be attainable using this approach.

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Analysis methodology for 3C-PIV data of rotary wing vortices

Cited by 83 publications

References 9 publications

A comprehensive PIV measurement campaign on a fully equipped helicopter model

A comprehensive PIV measurement campaign on a fully equipped helicopter model

Loose Fluid-Structure Coupled Approach for a Rotor in Descent Incorporating Fuselage Effects

Influence of Blade Aerodynamic Model on the Prediction of Helicopter High-Frequency Airloads

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