Mechanical Engineering - Research Publications

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End date: 2004 × Author: Marusic, Ivan × Subject: turbulent boundary layers ×

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    Observations on high Reynolds number turbulent boundary layer measurements
    HAFEZ, SHM ; MARUSIC, I ; CHONG, MS ; JONES, MB (The University of Sydney, 2004)
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    Dominant spanwise Fourier modes, and the existence of very large scale coherence in turbulent boundary layers
    Hutchins, N. ; Ganapathisubramani, B. ; Marusic, I. ( 2004)
    Multiple plane stereo PIV results and data from a rake often hot-wire probes are used to investigate the largest scalestructures in a zero-pressure-gradient turbulent boundary layer.Instantaneous vector fields from stereo PIV in spanwise-streamwiseplanes reveal long low- and high-speed regions,with a length that often exceeds the viewing window (> 2d).Also evident is a remarkable degree of spanwise organisation,that manifests as a persistent spanwise stripiness in the u componentof the PIV vector field. Almost all trace of such spanwiseorganisation is lost in the mean statistics, presumably dueto the multitude of scales naturally present in wall-bounded turbulence.This can be overcome by ‘de-jittering’ the instantaneousvector fields. By sorting the data according to dominantspanwise fourier modes, and then applying simple statisticaltools to the sorted subsets, we are able to extract a clear viewof spanwise organisation. Results are confirmed in the variousPIV data-sets. Since the PIV fails to adequately capture the fullstreamwise extent of the low-speed regions, a rake of hot-wireprobes is also employed to capture a continuous view of thespanwise coherence. It is found that the low-speed regions arein fact extremely persistent in the streamwise direction, oftenexceeding 20 d in length. The fact that these long features meanderappreciably in the spanwise direction will limit the overallstreamwise length-scale as witnessed by a single probe or singlepoint statistic. For instance, premultiplied one-dimensionalspectra of the streamwise velocity (kxFuu) at this z/d show apeak contribution for characteristic lengthscales of 5-7d.
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    Three dimensional structure characterization and visualization in a turbulent boundary layer
    Ganapathisubramani, B ; Longmire, E ; MARUSIC, I ; Urness, T ; Interrante, V (CIMNE - International Center for Numical Methods in Engineering, 2004)
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    New evolution equations for turbulent boundary layers in arbitrary pressure gradients
    Perry, A. E. ; Marusic, I. ; Jones, M. B. (Indian Academy of Sciences, 1998)
    A new approach to the classical closure problem for turbulent boundary layers is presented. This involves using the well-known mean-flow scaling laws such as Prandtl's law of the wall and the law of the wake of Coles together with the mean continuity and the mean momentum differential and integral equations. The important parameters governing the flow in the general non-equilibrium case are identified and are used for establishing a framework for closure. Initially, closure is done here empirically from the data but the framework is most suitable for applying the attached eddy hypothesis in future work. How this might be done is indicated here.