Mechanical Engineering - Research Publications

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    On the streamwise evolution of turbulent boundary layers in arbitrary pressure gradients
    Perry, A. E. ; Marusic, I. ; Jones, M. B. (Cambridge University Press, 2002)
    A new approach to the classic closure problem for turbulent boundary layers is presented. This involves, first, using the well-known mean-flow scaling laws such asthe log law of the wall and the law of the wake of Coles (1956) 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 achieved here empirically and the potential for achieving closure in the future using the wall-wake attached eddy model of Perry & Marusic (1995) is outlined. Comparisons are made with experiments covering adverse-pressure-gradient flows in relaxing and developing states and flows approaching equilibrium sink flow. Mean velocity profiles, total shear stress and Reynolds stress profiles can be computed for different streamwise stations, given an initial upstream mean velocity profile and the streamwise variation of free-stream velocity. The attached eddy model of Perry & Marusic (1995) can then be utilized, with some refinement, to compute the remaining unknown quantities such as Reynolds normal stresses and associated spectra and cross-power spectra in the fully turbulent part of the flow.
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    Investigation of three dimensionality in the near field of a round jet using stereo PIV
    Ganapathisubramani, B ; Longmire, EK ; Marusic, I (TAYLOR & FRANCIS LTD, 2002-03-21)
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    Self-propagating high-temperature synthesis of Ti3SiC2:: I, ultra-high-speed neutron diffraction study of the reaction mechanism
    Riley, DP ; Kisi, EH ; Hansen, TC ; Hewat, AW (WILEY, 2002-10)
    In situneutron diffraction at 0.9 s time resolution was used to reveal the reaction mechanism during the self‐propagating high‐temperature synthesis (SHS) of Ti3SiC2from furnace‐ignited stoichiometric 3Ti + SiC + C mixtures. The diffraction patterns indicate that the SHS proceeded in five stages: (i) preheating of the reactants, (ii) the α→β phase transformation in Ti, (iii) preignition reactions, (iv) the formation of a single solid intermediate phase in <0.9 s, and (v) the rapid nucleation and growth of the product phase Ti3SiC2. No amorphous contribution to the diffraction patterns from a liquid phase was detected and, as such, it is unlikely that a liquid phase plays a major role in this SHS reaction. The intermediate phase is believed to be a solid solution of Si in TiC such that the overall stoichiometry is ∼3Ti:1Si:2C. Lattice parameters and known thermal expansion data were used to estimate the ignition temperature at 923 ± 10°C (supported by the α→β phase transformation in Ti) and the combustion temperature at 2320 ± 50°C.