The ‘Chu-tube’: a velocimeter for use in highly-sheared, three-dimensional steady flows

Chu, J. K.; Rios-Chiquete, E.; Sarohia, S.; Bernstein, L.

doi:10.1017/s0001924000091399

“…A single-tube rotary yaw meter -broadly similar to the Chu-Tube (Chu et al 1987) -was designed and implemented (see Bertényi 2001 for details). This device is similar to a five-hole probe, but with a single chamfered tube rotated through four orthogonal positions and a sliding outer tube for the total pressure reading, resulting in a measurement volume under 1 mm 3 .…”

Section: Experimental Apparatus and Data Analysismentioning

confidence: 99%

Experimental observations of the merger of co-rotating wake vortices

Bertényi

¹

,

Graham

²

2007

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The interaction and merger of a pair of co-rotating vortices has been studied experimentally in a wind tunnel. The vortices are generated using two separate wings, allowing both initial circulation ratio and initial separation to be varied. At the nominal test speed of 30 ms−1, the circulation-based Reynolds number is typically 6.4 × 104. Mean crossflow velocities at stations downstream are obtained with a traverse-mounted yaw meter. The vortex interaction is characterized by fitting Lamb–Oseen profiles to the measured, azimuthally averaged, tangential velocity profiles.It is found that the merger process differs in several important respects from lower-Reynolds-number studies. First, the separation of the vortices decreases continually throughout the initial, ‘viscous growth’, phase, instead of remaining constant. Second, the vortex core growth in this phase appears to be greater than can be accounted for by turbulent diffusivity, even after correcting for the effects of wandering. Finally, the time to merger lies well below that predicted by expressions based on the lower-Reynolds-number observations, and is further reduced when the circulation ratio departs from unity. We conclude that the enhanced core growth is probably due to the short-wavelength ‘elliptic’ instability that has already been observed in some high-Reynolds-number experiments. The mechanism behind the decrease in separation, which is a crucial factor in the reduced merger time, is three-dimensional, but, beyond this, remains unknown.

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“…The yawmeter was manufactured in-house, and is a development of the 'Chu-tube' described in Ref. 4. On the basis of the discussion in Ref.…”

Section: Experimental Facility and Measurementsmentioning

confidence: 99%

“…Here the technique described in Ref. 4 was followed, with the exception that look-up tables, rather than curve-fits to the calibration variables, were employed to provide the link between measured pressures and flow velocities.…”

Section: Yawmeter Calibrationmentioning

confidence: 99%

The effect of flap-end additions on aircraft trailing vortices

Graham

¹

,

Berteny

²

,

Lee

³

2004

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The influence of flap-end geometry modifications on the near-field wake behind a generic high-lift wing/flap configuration is investigated experimentally with a single-tube yawmeter. It is found that flap-end additions tend to split the concentrated area of streamwise vorticity shed by the flap into two less intense regions, associated with the tips of the flap and the addition. For shorter additions, these regions tend to roll up together, resulting in a slightly more diffuse flap vortex of almost unchanged circulation. For larger additions, the outer region is captured by the tip vortex, which correspondingly gains in circulation at the expense of the flap vortex. In all cases, the vorticity centroid of the rolled-up wake is shifted outboard, and the overall circulation slightly increased. However, the associated lift increase implies a decrease in overall circulation at a given lift coefficient.

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“…Pressure tappings on the "body" were all on the turntable. A single-tube yaw meter, see Chu et a/< 14) , was used to measure the magnitude and direction of the mean velocity vector. This Chu-tube consists of two, concentric, hypodermic tubes, the inner of which is chamfered at 45° to its axis.…”

Section: Experimental Arrangementmentioning

confidence: 99%

On the effect of a strake-like junction fillet on the lift and drag of a wing

Bernstein

¹

,

Hamid

²

1996

Aeronaut. j.

6

0

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SummaryAn experimental study of the effects on the low-speed aerodynamic characteristics of a strake-like fillet is described, modelled on one used on an Airbus A320 variant fitted at the leading edge of a swept wing-plate junction. The wing, swept back at 20°, was of NACA 0015 section and chord 500 mm, both normal to its leading edge. A turbulent boundary layer had developed on the plate well ahead of the junction. The tests were conducted at a unit Reynolds number of 1.56 x 106 m-1.Surface pressure distributions were measured on the plate in the neighbourhood of the leading edge junction and also on the aerofoil and fillet at wing incidences of 0°, 3°, 6°, 9° and 12°. These were supplemented by surface oil-flow studies.The mean velocity and turbulence intensity fields around the leading edge were examined for incidences of 0° and 9°, using both a single tube yaw meter developed for the purpose and an X-wire anemometer. The X-wire anemometer was also used downstream of the trailing edge of the swept wing; five of the Reynolds stresses and the mean velocity field were measured.The sectional lift coefficients on the aerofoil were found to diminish as the junction was approached, slightly more so with the fillet than without it. The sectional drag coefficients due to pressure increased as the junction was approached, the fillet moderating this increase to only a small extent.However, the addition of the drooped fillet modified the flow considerably. The horseshoe-like vortex was less well defined than without it. At zero incidence, the peak in the turbulence intensity levels was virtually eliminated on what became effectively the compression side of the wing due to the local camber introduced by the asymmetric fillet. The turbulence levels were also reduced by the addition of the fillet at an incidence of 9°. However, the turbulent activity was spread through a larger proportion of the viscous region. The secondary flows and the turbulence activity in the wake are associated with unrecoverable kinetic energy and will be manifest as drag on the surfaces forming the junction.It is concluded that a carefully designed fillet, optimised for the cruise incidence of an aircraft, can reduce the peak turbulence levels in the junction. It remains unclear whether the total drag associated with the junction flow can be reduced significantly.However because of its effects on the turbulence, there may be other benefits, for example on the efficiency of downstream elements, such as fuselage-mounted engine intakes or the following stages of an axial flow machine. Junction fillets might also be used to control the scouring of river beds around bridge piers.

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The ‘Chu-tube’: a velocimeter for use in highly-sheared, three-dimensional steady flows

Cited by 8 publications

References 0 publications

Experimental observations of the merger of co-rotating wake vortices

Experimental observations of the merger of co-rotating wake vortices

The effect of flap-end additions on aircraft trailing vortices

On the effect of a strake-like junction fillet on the lift and drag of a wing

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