Reynolds Number Impact on Commercial Vehicle Aerodynamics and Performance

Wood, Richard M.

doi:10.4271/2015-01-2859

Cited by 16 publications

(10 citation statements)

References 209 publications

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“…Frank and Turney (2016) also show this effect can be significant, with a trailer absent any undercarriage/wheel contributions (similar to the current setup) being an overall negative contributor to total drag. Reynolds number and elevated solid model blockage ratio can also be further contributory factors (Wood 2015;Zdravkovich 2003).…”

Section: Pressure Measurementsmentioning

confidence: 99%

Influence of Rotating Wheels and Moving Ground Use on the Unsteady Wake of a Small-Scale Road Vehicle

Rejniak

Gatto

2020

Flow Turbulence Combust

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New insights into how different ground simulation methods affect road vehicle aerodynamics are presented. Experiments are conducted on a 1/24th-scale model, representative of a Heavy Goods Vehicle, at a Reynolds number, based on width of 2.3 × 10 5. Particular focus lay in characterising differences in unsteady wake development, with mean drag, base pressures, and wake velocities quantified, compared, and evaluated. Distinctly, these tests include the effects of elevated blockage ratio and wheel rotation. Results show moving ground use can have a substantial influence under these conditions, with increases in wake length and average base pressure coefficient of 17% and 9%, respectively. The dominant wake dynamics, characterised by a global streamwise oscillation commonly referenced as the bubble pumping mode, was also found dependent with asymmetric shedding frequencies from both vertical and horizontal base edges higher with static ground use. For these conditions, development of a low-frequency turbulence source, near omni-directional in nature, positioned behind the model, further contaminates the flow-field. This feature disappears with moving ground use. Both the nature and characteristics of the turbulence generated behind the wheels were also found to evolve differently, with a moving ground promoting stronger and more defined oscillatory behaviour up to model mid-height, two-and-a-half widths downstream. Overall, these results highlight that while variations in time-independent quantities to differing ground simulation can often be very subtle, prompting the interpretation of negligible overall effects, in-depth consideration from a time-dependent perspective may lead to a different conclusion.

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Section: Pressure Measurementsmentioning

confidence: 99%

Influence of Rotating Wheels and Moving Ground Use on the Unsteady Wake of a Small-Scale Road Vehicle

Rejniak

Gatto

2020

Flow Turbulence Combust

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“…Based on the frontal areas of the model and support structures, the solid blockage ratios for the three configurations were 11.2% (top), 10.8% (side) and 10.0% (front); all considerably below the 15% limit suggested in SAE J1252. 46 All data was corrected for blockage using Mercker's method, 47 with dynamic pressure and drag coefficient corrected by equations (1) and (2), respectively. This method was chosen based on its suitability for the test model chosen (sharper corners), facilitating some sensitivity to frontal separation.…”

Section: Mounting Configurationsmentioning

confidence: 99%

“…3 A dependency on Reynolds number, yaw orientation and model configuration was also found. 2,[9][10][11] Furthermore, Hetherington 3 shows the total force on a mounted ground vehicle model to be larger than the sum of the individual components (model and supports). Separate measurements using dummy supports (not connected) are normally used to correct such inconsistencies, [3][4][5] but a combination of both experimental and computational methodologies to obtain similar estimates can also be used, as outlined by Zhang et al 6 Many different road vehicle mounting techniques have been developed over the years, with each tending to be most suitable for specific test conditions and goals.…”

Section: Introductionmentioning

confidence: 99%

Upstream wind tunnel model mounting: The forgotten method for road vehicle aerodynamics

Rejniak

Gatto

2020

Proceedings of the Institution of Mechanical Engineers, Part D:

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A new method for supporting ground vehicle wind tunnel models is proposed. The technique employs a centrally mounted sting connecting the front face of the vehicle, adjacent to the floor, to a fixed point further upstream. Experiments were conducted on a 1/24th-scale model, representative of a Heavy Goods Vehicle, at a width-based Reynolds number of 2.3 × 105, with detailed comparisons made to more established support methodologies. Changes to mean drag coefficients, base pressures and wake velocities are all evaluated and assessed from both time-independent and time-dependent perspectives, with a particular focus within the wake region. Results show subtle changes in drag coefficient, together with discrete modifications to the flow-field, dependent on the method adopted. Subtle differences in base pressures and wake formation are also identified, with mounting the model upstream found to demonstrate retention of many of the beneficial effects of other techniques without suffering their deficiencies. Overall, these results identify the upstream mounting methodology as a viable alternative to currently available and more well-established techniques used to facilitate wind tunnel aerodynamic interrogation.

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“…Most of the published literature of vehicle aerodynamics is for open-road and windtunnel based modeling and experiments [49][50]. Moreover, the aerodynamic drag benefit is due to second generation devices like trailer skirts, trailer boat and gap reduction between tractor-trailer devices which were evaluated with track testing and CFD simulations from Surcel and Shetty [50].…”

Section: Introductionmentioning

confidence: 99%

“…In open road conditions, multiple vehicles in platooning configuration have shown a significant amount of aerodynamic drag variations [1,[35][36]. Recently, the importance of Reynolds number for CFD aerodynamics modeling was discussed in Wood [49].…”

Section: Introductionmentioning

confidence: 99%