Alistair Duff, for technical assistance Mr. Andrew Crockett, for strain gauge assistance
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9.2 ERRORSThe most probable error that occurred may have been through setting the air speed in the wind tunnel. As was detailed before, the true air speed was determined through taking readings from a manometer connected to a pitot tube, located in the upper region of the inlet mouth. The problem with this method is that the velocity profile across the test section is not uniform, and it is most likely that the values of velocity determined through the manometer readings, were consistently higher than the actual airflow velocity over the wing mirror. This lowered value of velocity over the wing mirror could be directly related to the lower values of drag obtained (compared to the CFD results), due to the fundamental relationship of drag stating that the drag increases proportionally with the velocity squared (E).  … E5
The relationship between drag and velocity may also explain why the two sets of data are more analogous at the lower speeds of 10 and 20mph where the velocity is less and therefore the effects of the velocity squared impact less on the values of drag. Furthermore, the fact that the wing mirror drag is almost negligible at low speeds such as 10mph makes the margin of error in taking readings larger. Another contribution of error may be attributed to the fact that the CFD analyses were modelled with the wing mirror mounted on a flat surface, whereas in the wind tunnel the wing mirror was placed in a small A-Pillar mock-up. The effects of the A-Pillar on the wing mirror drag are hard to quantify without the need of further testing, however, it may be a contributing factor. Download 3.93 Mb. Share with your friends:
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