Within the realm of fluid mechanics, there has always been an interest of bridging the gap between ideal- and real fluid flows. Pertaining to... Show moreWithin the realm of fluid mechanics, there has always been an interest of bridging the gap between ideal- and real fluid flows. Pertaining to the study of turbulent duct flow, an aspect ratio (AR) configuration that would behave in such a manner would be considered a critical aspect ratio. This would mean the flow core would be unaffected by any sidewall contributions. Such analysis is done through wall shear measurement techniques; this study used oil-film interferometry (OFI).The first steps of this study were to determine sufficient criteria to ensure that the data collected were representative of the tested configuration, e.g. parameter choice and flow development length. Previous studies used the bulk velocity U_b which is derived from the entirety of the flow. This study focuses on the flow core, thus the choice to use the center-line velocity U_C seemed appropriate. The development length pertains to testing downstream from the inlet such that parameters are independent in th`e streamwise direction. This study demonstrates that the previously held value of x/H = 100 is insufficient and that nearly twice that is required.Furthermore, this study shows three very important findings: the flow development length required for testing is x/H ≈ 200, the size of the test platform plays little part in the overall behavior of the flow, and that the critical aspect ratio is AR = 24. These findings correspond to an aspect ratio range of 12.8 ≤ AR ≤ 48 and a Reynolds number range of 0.5 × 10^4 < Re_H < 4.0 × 10^4 . From these data, the estimated relationship between the coefficient of friction and the Reynolds number is shown with the following relation:Cf,C = 0.05164 Re_H ^ −0.25 Show less
