Experimental Investigation of Dynamic Stall Performance for the EDI-M109 and EDI-M112 Airfoils

Gardner, Anthony Donald; Richter, Kai; Mai, Holger; Altmikus, Andree; Klein, Alexander; Rohardt, C.-H.

doi:10.4050/jahs.58.012005

Cited by 29 publications

(24 citation statements)

References 9 publications

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“…The experimental airloads coefficients are not corrected by the wind tunnel effects because well-established correction methods are not available for pitching airfoils tests, in particular for pitching cycles with highoscillation amplitudes. The standard deviation of the airloads coefficients are plotted on the experimental curves, as shown in the recent works by Gardner et al 18,23 The evaluation of the airloads standard deviation allows to evaluate the aperiodicity of the flow during the collected pitching cycles. In particular, the small values observed during the upstroke motion suggest the quite periodic behaviour of the flow during this phase of the motion.…”

Section: Numerical and Experimental Resultsmentioning

confidence: 99%

“…A wall boundary layer suction system was considered quite complex to be implemented together with an oscillating airfoil system; indeed, the known reference experimental activities about dynamic stall on pitching airfoils were carried out without suction. 12,[17][18][19] The driving mechanism is composed of a brushless servomotor and a 12:1 gear drive shaft. Two encoders are directly mounted on the external shaft on the other side of the model with respect to the motor: a 2048 imp/rev absolute digital encoder is used for feedback control and a 4096 imp/rev incremental analogue encoder is used to get the instantaneous position of the model.…”

Section: Experimental Set-upmentioning

confidence: 99%

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Experimental-numerical investigation of a pitching airfoil in deep dynamic stall

Zanotti

Melone²,

Nilifard

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part G:

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The results of a comprehensive experimental campaign are compared to computational fluid dynamics simulations results to assess the modelling capabilities for a NACA 23012 pitching airfoil in deep dynamic stall regime. The experimental campaign involved fast unsteady pressure measurements and particle image velocimetry. Two-dimensional simulations were carried out with EDGE, developed by FOI. The investigated test case consists in a sinusoidal pitching motion with a 10 amplitude and a reduced frequency of 0.1 around a mean angle of attack of 10 . The behaviour of the experimental lift and pitching moment coefficients is in close agreement with the two-dimensional simulations results, also during the downstroke motion where the flow field is characterised by severe unsteadiness conditions. A three-dimensional numerical model was built to evaluate the relevance of three-dimensional effects on the experiments. Three-dimensional simulations were carried out using the commercial code FLUENT. During upstroke motion, three-dimensional simulations results are in better agreement with the experiments, in particular in terms of the lift coefficient curve slope and of the pitching moment coefficient peak. The flow fields evaluated by particle image velocimetry surveys show strong vortical structures moving on the airfoil upper surface during the downstroke motion that are captured only by the three-dimensional model; then, the flow fields comparison demonstrates the importance of three-dimensional effects for a deep dynamic stall condition.

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Section: Numerical and Experimental Resultsmentioning

confidence: 99%

Section: Experimental Set-upmentioning

confidence: 99%

Experimental-numerical investigation of a pitching airfoil in deep dynamic stall

Zanotti

Melone²,

Nilifard

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…The twodimensional rotor blade airfoil model EDI-M109 was used (Gardner et al 2013a) and is built using the same footprint as the DSA-9A airfoil in the preceding section and installed in the DNW-TWG, as further described by Richter et al (2014).…”

Section: Transition Detection For the Pitching Edi-m109 Airfoilmentioning

confidence: 99%

“…Since many wind tunnel models are already equipped with surface pressure measurement, the method may require no additional instrumentation. The effect described in this paper has been used by the authors to describe the transition movement of periodically pitching helicopter airfoils experiencing dynamic stall in Gardner et al (2013a) and Richter et al (2013), although the systematic comparison against other transition measurement methods was not applied at that time.…”

Section: Introductionmentioning

confidence: 95%

Boundary layer transition determination for periodic and static flows using phase-averaged pressure data

Gardner

Richter

2015

Exp Fluids

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the power required. Additionally the transition affects the resistance of components to boundary layer separation.As seen in Fig. 1 on the example of a flat plate, the boundary layer is characterised by a laminar part near the leading edge which has low turbulence and wall shear stress. At some point, turbulence in the boundary layer is no longer damped, and the turbulence increases along a "transition region" until the boundary layer is fully turbulent. Compared to the laminar region, the turbulent region has higher recovery temperature, wall heat flux, wall shear stress, and higher RMS values of wall static pressure, Pitot pressure and heat flux (Schlichting and Gersten 2006). These characteristics can be used to detect transition, and the detection of boundary layer transition can be performed by a large number of methods (Nitsche and Brunn 2006), most of which work for transition positions which are invariant with time or quasi-steady with regard to the surface temperature distribution, for example: --Skin friction measurements by piezoelectric sensors (Nitsche and Brunn 2006) or oil films for steady flows (Tanner and Blows 1976) or unsteady flows (Schülein 2014). --Measurements of the transition position by sublimation (Velkoff et al. 1971) or China-clay (Richards and Burstall 1945). --Measurements of the wall recovery temperature by thermocouples, temperature-sensitive paint, temperaturesensitive liquid crystals or infrared cameras (Peake et al. 1977). --Measurements of the wall heat transfer by thermocouples, infrared cameras, or direct measurements by hotfilm anemometers (Schultz and Jones 1973). --Measurements of the boundary layer velocity profile by hot-wire anemometers, Pitot tube or PIV (Nitsche and Brunn 2006).Abstract A method of boundary layer transition measurement is presented for wind tunnel models instrumented with surface pressure taps. The measurement relies on taking a number of theoretically identical measurements at different times and then analysing the standard deviation of the pressures. Due to the slight unsteady movement of the transition position, a peak in the standard deviation of pressure σ C P peak is found at the transition position, and this is correlated with measurements of the transition position with an infrared camera and hot-film anemometers. In contrast to microphone measurements, it is shown that the transition detection works for data which have been low-pass filtered with a cut-off of 1 Hz. The application to static and dynamic transition measurements on static and periodically pitching helicopter rotor blade airfoils at Mach 0.3-0.5 is demonstrated.

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“…A further comparison between the two airfoils for the DS2 test case based on the wind tunnel measurements is given in Ref. 9. Three-dimensional and particularly wind tunnel sidewall effects were considered the main reasons for the overestimation of the vortex magnitudes in the 2D calculations.…”

Section: D Airfoil Simulationmentioning

confidence: 99%

Numerical Comparison of Dynamic Stall for Two-Dimensional Airfoils and an Airfoil Model in the DNW–TWG

Klein¹,

Lutz²,

Krämer³

et al. 2012

j am helicopter soc

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The airfoil sections of helicopter rotors experience a wide range of flow conditions in forward flight from transonic flow on the advancing blade to subsonic flow and high angles of attack on the retreating blade. Most notably, the dynamic stall phenomenon has been a research topic for decades and various models have been introduced to predict the unsteady characteristics of the rotor blade undergoing unsteady separation. The objective of the present paper is to compare twodimensional (2D) dynamic stall computations, suitable for airfoil design studies considering unsteady characteristics, with computational fluid dynamics simulations of the wind tunnel environment taking into account three dimensionality and wall effects. Differences between experiment and 2D computations can be partly attributed to sidewall effects, which alter the effective angle of attack at the midsection pressure measurement plane. To gain more insight into these effects, investigations are presented, which show the wind tunnel wall boundary layers and separation effects at the sidewall-airfoil junction.

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Experimental Investigation of Dynamic Stall Performance for the EDI-M109 and EDI-M112 Airfoils

Cited by 29 publications

References 9 publications

Experimental-numerical investigation of a pitching airfoil in deep dynamic stall

Experimental-numerical investigation of a pitching airfoil in deep dynamic stall

Boundary layer transition determination for periodic and static flows using phase-averaged pressure data

Numerical Comparison of Dynamic Stall for Two-Dimensional Airfoils and an Airfoil Model in the DNW–TWG

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