Yazar "Alveroğlu, Burhan" seçeneğine göre listele

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    On the instability of Ekman boundary-layer flow over a rough disk with a wavy surface profile
    (Wiley, 2021) Alveroğlu, Burhan
    We apply the method of lines and the backward difference method to solve highly nonlinear governing mean flow equations of the Ekman boundary-layer flow over a rough disk with a wavy surface profile. These equations are derived using the YHP roughness model that imposes a wavy surface profile in terms of the radial position r, assuming rotational symmetry. Our main interest is to determine the effect of roughness on the local linear convective instability of the Ekman flow, and we solve the local linear stability equations of the disturbances stationary relative to the disk using the Chebyshev polynomials. The crossflow and viscous types of instability modes, the Type I and Type II modes respectively, are analyzed. Our theoretical findings prompts that an adequately designed rough disk can be a useful tool for a passive flow-control method for the Ekman flow. The underlying physical mechanisms are investigated applying a fundamental energy analysis.
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    On the Mean Flow Solutions of Related Rotating Disk Flows of the BEK System
    (Fuat USTA, 2020) Alveroğlu, Burhan
    This paper investigates the effects of the YHP roughness model on the mean flow solutions of some flows belong to the family of the rotating BEK system flows. The governing mean flow equations are formulated in the rotating frame of reference, therefore, they include terms arising from the centrifugal force. These mean flow equations are solved using the method of lines and the backward difference method. Then, obtained results are compared for specifically selected value of roughness parameters with the results of a fundamentally different roughness model, the MW model. The results of the YHP model reveal that applying surface roughness changes the characteristics of the mean flow components. Moreover, the comparison of the YHP and MW models points that these changes are notably different for each model. Therefore, possible future researches can be conducted to investigate the stability characteristics of the flows due to the selection of the roughness model.
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    The instability of non-Newtonian boundary-layer flows over rough rotating disks
    (Elsevier, 2019) Alqarni, A. A.; Alveroğlu, Burhan; Griffiths, P. T.; Garrett, S. J.
    We are concerned with the local linear convective instability of the incompressible boundary-layer flows over rough rotating disks for non-Newtonian fluids. Using the Carreau model for a range of shear-thinning and shear-thickening fluids, we determine, for the first time, steady-flow profiles under the partial-slip model for surface roughness. The subsequent linear stability analyses of these flows (to disturbances stationary relative to the disk) indicate that isotropic and azimuthally-anisotropic (radial grooves) surface roughness leads to the stabilisation of both shear-thinning and -thickening fluids. This is evident in the behaviour of the critical Reynolds number and growth rates of both Type I (inviscid cross flow) and Type II (viscous streamline curvature) modes of instability. The underlying physical mechanisms are clarified using an integral energy equation.