An experimental study of the effect of free-stream turbulence on a trailing vortex

Beninati, M. L.; Marshall, J. S.

doi:10.1007/s00348-004-0904-1

Cited by 34 publications

(13 citation statements)

References 26 publications

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“…8b it is interesting to observe that in correspondence to the mean vortex center location this anisotropy vanishes by high-pass filtering the velocity signals; in fact, for the highest cut-off frequency VW=r V r W becomes roughly zero at r/c = 0. This indicates that the flow anisotropy is an effect only of wandering and not a general characteristic of all scales of the vorticity structures, at variance with the findings of Beninati and Marshall (2005).…”

Section: Wandering Statistical Simulationssupporting

confidence: 56%

“…In analogy with the spectral analysis performed by Beninati and Marshall (2005), the chosen cut-off frequencies correspond to wavelengths that are multiples of the core radius, i.e., 200, 100, 30 and 10 times the core radius (the considered r 1 value is about 0.05c). Therefore, the used cut-off frequencies were f th1 = 4 Hz, f th2 = 8 Hz, f th3 = 27 Hz and f th4 = 81 Hz; these values correspond, respectively, to non-dimensional frequencies (fc/ U ? )…”

Section: Flow Field Analysismentioning

confidence: 99%

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Correction of wandering smoothing effects on static measurements of a wing-tip vortex

2008

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Wandering is a typical feature of wing-tip vortices and it consists in random fluctuations of the vortex core. Consequently, vortices measured by static measuring techniques appear to be more diffuse than in reality, so that a correction method is needed. In the present paper statistical simulations of the wandering of a Lamb-Oseen vortex are first performed by representing the vortex core locations through bi-variate normal probability density functions. It is found that wandering amplitudes smaller than 60% of the core radius are well predicted by using the ratio between the RMS value of the mean cross-velocity and its slope measured at the mean vortex center. Furthermore, the principal axes of wandering can be accurately evaluated from the opposite of the cross-correlation coefficient between the spanwise and the normal velocities measured at the mean vortex center. The correction of the wandering smoothing effects is then carried out through four different algorithms that perform the deconvolution of the mean velocity field with the probability density function that represents the wandering. The corrections performed are very accurate for the simulations with wandering amplitudes smaller than 60% of the core radius, whereas errors become larger with increasing wandering amplitudes. Subsequently, the whole procedure to evaluate wandering and to correct the mean velocity field is applied to static measurements, carried out with a fast-response five-hole pressure probe, of a tip vortex generated from a NACA 0012 half-wing model. It is found that the wandering is predominantly in the upward-outboard to downward-inboard direction. Furthermore, the wandering amplitude grows with increasing streamwise distance from the wing, whereas it decreases with increasing angle of attack and free-stream velocity.

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Section: Wandering Statistical Simulationssupporting

confidence: 56%

Section: Flow Field Analysismentioning

confidence: 99%

Correction of wandering smoothing effects on static measurements of a wing-tip vortex

2008

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“…Similar to the earlier study by Bandyopadhyay et al (1991) was an experimental study of a trailing vortex immersed in an external grid-generated turbulence field carried out by Beninati and Marshall (2005). They sought to add to the knowledge of how a vortex interacts with external turbulence, citing a lack of literature on the problem (despite its importance) as motivation.…”

Section: Experimental Investigations Of Wing-tip Vortices In the Nearmentioning

confidence: 99%

Numerical and experimental investigation of the mean and turbulent characteristics of a wing-tip vortex in the near field

O’Regan

Griffin

Young

2014

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…Velocity and pressure field measurements in the wake of an aircraft model are a valuable resource in predicting the performance characteristics of the aircraft (Spalart 1998b;Rossow 1999), as well as a means to investigate the more fundamental nature of vortex flows (see, for example, Bandyopadhyay et al (1991) and Phillips & Graham (1984)). However, single-point scans of vortex flows (such as the hot-wire and multi-hole pressure probe data of Beninati & Marshall (2005), Birch et al (2004), Birch & Lee (2005), Chow et al (1997) and Dacles-Mariani et al (1995), to list but a few) will tend to underpredict vortex strength owing to the smoothing effect of vortex 'meandering', or the random, low-frequency modulation in the trajectory of the vortex centre. While a number of schemes have been proposed to correct single-point scans of vortex wakes for the effect of meandering (such as those of Devenport et al (1996), Bailey & Tavoularis (2008) and Iungo et al (2009)), it has also been shown that, with meandering amplitudes which are large but within the range of those observed experimentally, the reconstruction of the vortex velocity field from point measurements becomes impossible (Birch 2012).…”

Section: Introductionmentioning

confidence: 99%

Tracer particle momentum effects in vortex flows

Birch¹,

Martin²

2013

J. Fluid Mech.

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The measurement of vortex flows with particle-image velocimetry (PIV) is particularly susceptible to error arising from the finite mass of the tracer particles, owing to the high velocities and accelerations typically experienced. A classical model of Stokes-flow particle transport is adopted, and an approximate solution for the case of particle transport within an axisymmetric, quasi-two-dimensional Batchelor q-vortex is presented. A generalized expression for the maximum particle tracking error is proposed for each of the velocity components, and the importance of finite particle size distributions is discussed. The results indicate that the tangential velocity component is significantly less sensitive to tracking error than the radial component, and that the conventional particle selection criterion (based on the particle Stokes number) may result in either over-or under-sized particles for a specified allowable error bound. Results were demonstrated by means of PIV measurements carried out in air and water using particles with very different properties.

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An experimental study of the effect of free-stream turbulence on a trailing vortex

Cited by 34 publications

References 26 publications

Correction of wandering smoothing effects on static measurements of a wing-tip vortex

Correction of wandering smoothing effects on static measurements of a wing-tip vortex

Numerical and experimental investigation of the mean and turbulent characteristics of a wing-tip vortex in the near field

Tracer particle momentum effects in vortex flows

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