Car-Wake Imaging Using a Seven-Hole Probe

Cogotti, A.

doi:10.4271/860214

Cited by 22 publications

(12 citation statements)

References 4 publications

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“…Downstream of the base separation bubble, two streamwise vorticies are formed which dominate the farwake. The location and characteristics of these vorticies have been documented by several researchers using total pressure, multi-hole, and hot-wire probes [9,11,12,13,14]. Their results show single and multiple vortices that move toward the ground and away from the center plane with increasing downstream distance.…”

Section: Flow Separation On a Notchback Rear Endmentioning

confidence: 93%

“…Hucho [5] suggests that the higher aspect ratio of the backlight on notchbacks produces a weaker vortex. This may explain why the C-pillar vortex is not as apparent in wake measurements by numerous researchers [11,12,13,14]. Although some computational investigations [9,12,13] have predicted several vortex pairs in the near-wake of notchback configurations, it cannot be determined which, if any, may be C-pillar vortices.…”

Section: Flow Separation On a Notchback Rear Endmentioning

confidence: 98%

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An Experimental Investigation of the Flow Over the Rear End of a Notchback Automobile Configuration

Luther¹

2000

SAE Technical Paper Series

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An experimental investigation of the flow over the rear end of a 0.16 scale notchback automobile configuration has been conducted in the NASA Langley Basic Aerodynamics Research Tunnel (BART). The objective of this work was to investigate the flow separation that occurs behind the backlight and obtain experimental data that can be used to understand the physics and timeaveraged structure of the flow field. A three-component laser velocimeter was used to make non-intrusive, velocity measurements in the center plane and in a single cross-flow plane over the decklid. In addition to off-body measurements, flow conditions on the car surface were documented via surface flow visualization, boundary layer measurements, and surface pressures. The experimental data show several features previously identified by other researchers, but also reveal differences between the flow field associated with this particular configuration and the generally accepted models for the flow over a notchback rear end.

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Section: Flow Separation On a Notchback Rear Endmentioning

confidence: 93%

Section: Flow Separation On a Notchback Rear Endmentioning

confidence: 98%

An Experimental Investigation of the Flow Over the Rear End of a Notchback Automobile Configuration

Luther¹

2000

SAE Technical Paper Series

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“…Gaylard et al [4] compiled a number of cases (eg: [5], [6], [7], [8], [9]) in which asymmetry has been observed in the wake structure of notchback vehicle types, including real vehicles and idealized geometries. In most cases these observations were anecdotal to the subject of the original investigation.…”

Section: Figure 1 Definition Of Effective Backlight Anglementioning

confidence: 99%

Links between Notchback Geometry, Aerodynamic Drag, Flow Asymmetry and Unsteady Wake Structure

Sims-Williams¹,

Marwood²,

Sprot³

2011

SAE Int. J. Passeng. Cars – Mech. Syst.

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. (2011) 'Links between notchback geometry, aerodynamic drag, ow asymmetry and unsteady wake structure.', SAE International journal of passenger cars. Mechanical systems., 4 (1). pp. 156-165. Further information on publisher's website:http://dx.doi.org/10.4271/2011-01-0166Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTThe rear end geometry of road vehicles has a significant impact on aerodynamic drag and hence on energy consumption. Notchback (sedan) geometries can produce a particularly complex flow structure which can include substantial flow asymmetry. However, the interrelation between rear end geometry, flow asymmetry and aerodynamic drag has lacked previous published systematic investigation.This work examines notchback flows using a family of 16 parametric idealized models. A range of techniques are employed including surface flow visualization, force measurement, multi-hole probe measurements in the wake, PIV over the backlight and trunk deck and CFD.It is shown that, for the range of notchback geometries investigated here, a simple offset applied to the effective backlight angle can collapse the drag coefficient onto the drag vs backlight angle curve of fastback geometries. This is because even small notch depth angles are important for a sharp-edged body but substantially increasing the notch depth had little further impact on drag.This work shows that asymmetry originates in the region on the backlight and trunk deck and occurs progressively with increasing notch depth, provided that the flow reattaches on the trunk deck and that the effective backlight angle is several degrees below its crucial value for non-reattachment. A tentative mapping of the flow structures to be expected for different geometries is presented.CFD made it possible to identify a link between flow asymmetry and unsteadiness. Unsteadiness levels and principal frequencies in the wake were found to be similar to those for high-drag fastback geometries. The shedding of unsteady transverse vortices from the backlight recirculation region has been observed.

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“…In the literature, a large number of papers where the experimental results were obtained using this measurement technique can be found, e.g. those reported by Hackett and Sugavanam [2], Hackett et al [3], Coggotti [4,5] and Silva and Viegas [6].…”

Section: Introductionmentioning

confidence: 99%

“…Those problems were overcome, firstly with the introduction of non-nulling calibration methods (Ostowari and Wentz [7]), and secondly with the sevenhole geometry that allowed, with the quite ingenious measuring method proposed by Gallington and Sisson [1], the increase of the sensitivity solid angle until values around 70°. To reduce the blind part of the probe, a new geometry using two seven-hole probes in opposite senses was proposed, resulting on the fourteen-hole probe (Cogotti [5]). …”

Section: Introductionmentioning

confidence: 99%

On the use of a linear interpolation method in the measurement procedure of a seven-hole pressure probe

Silva

Pereira

Cruz³

2003

Experimental Thermal and Fluid Science

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Calibration and measurement procedures implemented to work with a seven-hole directional pressure probe in the mapping of pressure and velocity wind tunnel flows are reported in this paper. The performances of two different methods used to derive the flow characteristics (direction and magnitude of flow velocity vector and total and dynamic pressure) from the seven pressure values measured by the probe, are comparatively evaluated. The conventional method, based upon the fitting of the calibration directional data with fourth order polynomial functions is compared with a new method where direct linear interpolation is performed over the calibration matrices. Besides the comparison of the two methods, the fundamentals of the working procedure of the probe are briefly explained and an example of the mapping of the flow field around a wing model in a wind tunnel experiment is presented.

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Car-Wake Imaging Using a Seven-Hole Probe

Cited by 22 publications

References 4 publications

An Experimental Investigation of the Flow Over the Rear End of a Notchback Automobile Configuration

An Experimental Investigation of the Flow Over the Rear End of a Notchback Automobile Configuration

Links between Notchback Geometry, Aerodynamic Drag, Flow Asymmetry and Unsteady Wake Structure

On the use of a linear interpolation method in the measurement procedure of a seven-hole pressure probe

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