Mechanical Engineering - Research Publications

Permanent URI for this collection

Search Results

Now showing 1 - 4 of 4
  • Item
    Thumbnail Image
    A wall-wake model for the turbulence structure of boundary layers. Part 2. Further experimental support
    Marusic, I. ; Perry, A. E. (Cambridge University Press, 1995)
    In Part 1 an extension of the attached eddy hypothesis was developed and applied to equilibrium pressure gradient turbulent boundary layers. In this paper the formulation is applied to data measured by the authors from non-equilibrium layers and agreement with the extended theory is encouraging. Also power spectra of the Reynolds stresses as developed from the extended theory compare favourably with experiment. The experimental data include a check of cone-angle effects by using a flying hot wire.
  • Item
    Thumbnail Image
    A wall-wake model for the turbulence structure of boundary layers. Part 1. Extension of the attached eddy hypothesis
    Perry, A. E. ; Marusic, I. (Cambridge University Press, 1995)
    The attached eddy hypothesis developed for zero pressure gradient boundary layers and for pipe flow is extended here to boundary layers with arbitary streamwise pressure gradients, both favourable and adverse. It is found that in order to obtain the correct quantitative results for all components of the Reynolds stresses, two basiv types of eddy structure geometries are required. The first type, called type-A, is interpreted to give a 'wall structure' and the second, referred to as type-B, gives a 'wake structure'. This is an analogy with the conventional mean velocity formulation of Coles where the velocity is decomposed into a law of the wall and a law of the wake.If the above mean velocity formulation is accepted, then in principle, once the eddy geometries are fixed for the two eddy types, all Reynolds stresses and associated spectra contributed from the attached eddies can be computed without any further empirical constants. This is done by using the momentum equation and certain convolution integrals developed here based on the attached eddy hypothesis. The theory is developed using data from equilibrium and quasi-equilibrium flows. In Part 2 the authors' non-equilibrium data are used.
  • Item
    Thumbnail Image
    Similarity law for the streamwise turbulence intensity in zero-pressure-gradient turbulent boundary layers
    Marusic, I. ; Uddin, A. K. M. ; Perry, A. E. ( 1997)
    A similarity relationship is proposed to describe the streamwise broadband-turbulence intensity in a zero-pressure-gradient boundary layer. The formulation is applicable to the entire region of the flow beyond the viscous buffer zone and is based on the attached eddy hypothesis, the Reynolds-number-similarity hypothesis and the assumed existence of Kolmogorov eddies with a universal inertial subrange. Experimental data of the authors and those from various published works covering a large Reynolds number range are investigated in light of this formulation.
  • Item
    Thumbnail Image
    On the validity of Taylor's hypothesis in wall turbulence
    Uddin, A. K. Mesbah ; Perry, A. E. ; MARUSIC, IVAN ( 1997)
    The validity of Taylor’s hypothesis of frozen turbulence has been the issue of much debate, especially when applied to flows with strong shear and high turbulence intensities. In the past, Taylor’s hypothesis was used by various researchers for the quantitative interpretation of the structure angle of the eddies on the basis of double-velocity correlations (eg. Alving et al. [1]) or velocity-wall pressure or velocity-wall shear stress correlations (e.g. Brown & Thomas [2] , Rajagopalan & Antonia [6]. In light of the ambiguity associated with Taylor’s hypothesis, naturally, there are resultant uncertainties in terms of the measured structure angle. Subsequently there is a need to investigate how do these uncertainties effect the structure angle measurements and as well as to examine the validity of Taylor’s hypothesis when applied to two-point double-velocity correlation measurements in an anisotropic shear flow.