Mechanical Engineering - Research Publications

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    Surface shear stress fluctuations in the atmospheric surface layer
    Monty, J. P. ; Chong, M. S. ; Hutchins, N. ; Marusic, I. ( 2006)
    A lightweight, high frequency response, floating element sensor was used to measure wall shear stress fluctuations in an atmospheric surface layer. The sensor uses a laser position measurement system to track the motion of the floating element. The measurements were taken as part of an internationally coordinated experimental program designed to make extensive spatial and temporal measurements of velocity, temperature and wall shear stress of the surface layer. Velocity measurements were made with both a 27m high vertical array and a 100m wide horizontal array of sonic anemometers; 18 anemometers in total were employed. Cross-correlations of shear stress and streamwise velocity fluctuations were analysed in an attempt to identify structure angles in the flow. The results were shown to compare favourably with experimental data from controlled, laboratory turbulent boundary layer measurements at three orders of magnitude lower Reynolds number.
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    Inclined cross-stream stereo PIV measurements in turbulent boundary layers.
    Hutchins, N. ; Hambleton, W. ; Marusic, I. (CIMNE, 2004)
    By arranging the laser light-sheet and image plane of a stereo PIV system ininclined spanwise/wall-normal planes (inclined at both 45± and 135± to the x-axis) we have obtained a unique quantitative view of the turbulent boundarylayer in planes aligned both with and against the principle vorticity axis of aproposed hairpin model. These experiments have been repeated across a range ofReynolds numbers (Re¿ ¼ 800 ¡ 3050). In-plane swirl results indicate the presenceof inclined eddies, arranged about low-speed regions (with circumstantialevidence suggesting that these occasionally group into packet-like formations).Two-point correlations show that outer scaling is the correct way to quantifythe characteristic spanwise lengthscale across the range of Re¿ .