From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparison of aerodynamic drag data from wind tunnel tests on Derby and French Streamline Bentley models.
| Identifier | ExFiles\Box 161\1\ scan0189 | |
| Date | 5th November 1937 guessed | |
| -2- A.{Mr Adams} Derby Streamline Bentley .88 B. French Streamline Bentley .500 It will be recalled that the French model was very steady in the tunnel, indicating a less turbulent flow. The following points occur to us:- (1) Because of the difference in flow between the two models it occurs to us from our rather elementary knowledge of aerodynamics that the two models may have different curves of drag co-efficient plotted against the Reynolds number. In other words 'K' is not a constant, but the curve for 'A' is approximately a straight line between the model and the car, whereas that for 'B' may not have the same slope, or may even not be a straight line. We notice that in the case of model 'A' the drag co-efficient is falling with increase in velocity whilst that of model 'B' is rising. We wonder whether the differences concerned are more than those to be expected by experimental error. (2) May not the different model scales effect the tunnel drag, due to the reaction from the flat plate ground? We would esteem it a great favour if you would tell us whether, from your experience with the use of models of varying flow characteristics in this tunnel, you can throw any light on this problem. The 'K' for the French Car ( made to model B) is .001475. Yours faithfully, FOR ROLLS-ROYCE LIMITED. CAR PROJECT OFFICE. | ||