Experimental Data for the Validation of Numerical Methods - SAE Reference Notchback Model

Abstract

The use of simulation tools by vehicle manufacturers to design, optimize and validate their vehicles is essential if they are to respond to the demands of their customers, to meet legislative requirements and deliver new vehicles ever more quickly. The use of such tools in the aerodynamics community is already widespread, but they remain some way from replacing physical testing completely. Further advances in simulation capabilities depend on the availability of high quality validation data so that simulation code developers can ensure that they are capturing the physics of the problems in all the important areas of the flow-field. This paper reports on an experimental program to generate such high quality validation data for a SAE 20 degree backlight angle notchback reference model. This geometry is selected as a particularly powerful test case for the development and validation of numerical tools because the flow exhibits a realistic impingement and A pillar regime, significant three dimensional structures and the backlight/boot-deck exhibits a local separation and reattachment. The paper includes force and moment data, surface pressures for the centerline, slant, boot-deck and base and detailed PIV data for the impingement region, model centerline, A pillar and multiple planes on the slant and boot-deck. Time averaged, statistical and instantaneous data are presented.Results are discussed with regard to the overall flow features, the correlation between the different data sets and the accuracy and limitations of each of the experimental techniques in this particular application. Example data is included throughout the paper and full data sets are freely available in the Loughborough University Institutional Repository as a resource for future code development.

Influence of Short Rear End Tapers on the Unsteady Base Pressure of a Simplified Ground Vehicle

“…In both the cases, the tappings were placed across the whole width of the base, with a finer distribution close to the edges in order get a more accurate representation of the pressure distribution in the region with the highest gradients (as shown in Figure 3). Pressure samples were collected at 260 Hz, for two different sampling times T S , respectively equal to 31.5 s and 630.0 s. Pressure signal distortion caused by the tubes connecting the model surface to the pressure scanners was removed using the same experimentally derived correction function proposed by Sims-Williams and Dominy in [23] and implemented by Wood et al in [24].…”

The Study of a Bi-Stable Wake Region of a Generic Squareback Vehicle using Tomographic PIV

“…The use of two component, two dimensional PIV is well documented in a variety of situations [4,7,8,9,10] and traditionally involves a single camera that is normal to the measurement plane, a pulsed laser passing through a plano-concave lens to create a diverging sheet of light focused to a thickness of around 1mm, neutrally buoyant seeding particles (such as DEHS solution which has been atomized to form 1μm particles) and a computer containing a timing board that allows for the control of the system. This technique is particularly accurate when there is only a small amount of through plane motion so that the majority of the particles captured by the camera in the double frame image pair remain within the light sheet.…”

High-order detached-eddy simulation of external aerodynamics over an SAE notchback model

“…The experimental measurements were sampled for 30 seconds to obtain the mean values for lift C l and drag C d coefficients. The reported accuracy (10) of the underfloor balances were ±2 drag counts or 0.002 for a 1/4 scale model.…”

“…The experimental measurements were taken inside Loughborough University's 1.9 × 1.3 m wind tunnel. The inlet conditions were set to a maximum incident velocity of 40 m/s ± 0.4 m/s and a measured turbulence intensity of 0.2% (10) . The resulting flow field around the High-order DES over an SAE notchback model car was expected to be relatively Reynolds number insensitive.…”

“…There were two important changes that have an impact on the mean force coefficients, the underbody diffuser and smooth longitudinal edges of the notchback. The longitudinal edges were originally smooth for the notchback model provided through the Loughborough Repository, which differed from the the figures presented by Wood et al (10) ; however, this was altered in a later revision to the Loughborough Repository (7) . The information on the sharpedge model was only made available after the simulations were completed, and it was not practical to change them at the time of writing.…”