The influence of an afterbody on an axisymmetric wake flow is investigated with two-component particle image velocimetry at a Reynolds number of R e D = 6.7 · 10 4 based on the model diameter. The reattachment distance is found to vary from two to four step heights as the afterbody diameter is increased. Measurements performed on equivalent planar backward-facing step geometries reveal that the reattachment length scales similarly to a planar backward-facing step when the afterbody to main-body diameter ratio approaches unity. The distribution of turbulent normal and shear stresses reveals a progressive inhibition of the radial fluctuations for increasing afterbody diameter, whereas a proper orthogonal decomposition analysis highlights a concurrent weakening of the shear-layer flapping mode. For d / D 0.4 , the frequency spectrum of the time coefficient of the first proper orthogonal decomposition mode appears associated with the wake flapping motion and peaks in the range of S t D = 10 3 10 2 . This frequency is associated with the recirculating flow unsteadiness observed in the azimuthal plane of the wake. The configuration without afterbody features an additional contribution at S t D = 0.2 , which is associated with vortex shedding. The current results reveal the dependence of low-frequency unsteadiness upon changes in the afterbody diameter.


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    Title :

    Afterbody Effects on Axisymmetric Base Flows


    Contributors:

    Published in:

    AIAA Journal ; 54 , 8 ; 2285-2294


    Publication date :

    2016-08-01




    Type of media :

    Conference paper , Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




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