| The turbulent boundary layer is a critical aspect of most engineering applications involving fluid flow or heat transfer. Unfortunately, many engineering applications involve complex boundary layers at high Reynolds numbers, and cannot be accurately calculated. Since most experiments are done at low Reynolds number, an understanding of Reynolds number scaling is fundamentally important for accurate prediction of practical flows.; Two-component velocity measurements were taken with a custom-built high-resolution laser Doppler anemometer system. Flat plate boundary layer data are presented over a momentum thickness Reynolds number range from 1500 to 31000. In contrast to most previous findings, the Reynolds shear stress and wall-normal Reynolds normal stress show a high degree of self-similarity above Re &thetas; = 2000, when normalized by the friction velocity squared. The streamwise Reynolds normal stress, however, does not, and empirical evidence suggests that the proper scaling is the product of the friction velocity and the freestream velocity. Using this scaling, the streamwise normal stress is well collapsed over the Reynolds number range studied.; The swept and unswept bump flows are studied over a Reynolds number range from 2000 to 24000. These are highly non-equilibrium boundary layers, which undergo multiple changes in streamwise pressure gradient and curvature, with the addition of cross-flow for the swept bump. Although the downstream recovery of the bump flows to an equilibrium flat plate boundary layer is rapid, the flows are strongly Reynolds number dependent in some regions. This is attributed to a dependence on additional length scales, such as bump height or radius of curvature. Since these geometric length scales are fixed, while the inner length scales of the turbulence are a strong function of Reynolds number, any flow phenomena which is dependent on the ratio of these scales must be Reynolds number dependent. This implies that turbulence models based on equilibrium boundary layers and low Reynolds number experiments will not be accurate when extended to higher Reynolds numbers. |
