Yazar "Hassanzadeh, Rahim" seçeneğine göre listele

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    Large eddy simulation of flow around two side-by-side spheres
    (KOREAN SOC MECHANICAL ENGINEERS, 2013) Hassanzadeh, Rahim; Sahin, Besir; Ozgoren, Muammer
    Large eddy simulation, using a dynamic Smagorinsky sub-grid scale, is used for the prediction of flow structures around two identical spheres fixed side-by-side at a subcritical flow regime with the Reynolds number equal to 5,000. The QUICK discretization method is applied to discretize the convection terms of the Navier-Stokes equation by means of the finite volume approach. This work focuses mainly on the wake structures downstream of the two interactive spheres located at three various dimensionless separation distances between spheres such as G/D = 1.50, 2.00, and 3.00. The obtained results revealed that the interaction between wakes affects the flow structures downstream of spheres. The rate of this interaction is strongly altered as a function of separation distance. On the other hand, some flow data such as mean drag and mean lift coefficients are affected due to the wake interactions. Finally, examination of the Reynolds stress variation along the different lateral axis, L/D, revealed that the nozzle effect does not play a significant role on the turbulence characteristics beyond the G/D = 3.00.
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    Large Eddy Simulation of Free-Surface Effects on the Wake Structures Downstream of a Spherical Body
    (Permagon-Elsevıer Scıence Ltd, 2012) Hassanzadeh, Rahim; Şahin, Beşir; Özgören, Muammer
    The wake structure downstream of a solid body, which moves near the free-surface, is under the influence of the free-surface motion. The rate of this influence depends on the submerging elevation or distance between the solid body and the free-surface. This investigation presents the interaction between the free-surface and the wake structure downstream of a spherical body at four different submerging elevations such as h/d=0.25, 0.50, 1.00 and 2.00 for the Reynolds number of 5000. For the present study, large eddy simulation (LES) using a dynamic Smagorinsky sub-grid stress (SGS) is applied on the hybrid grid system according to an advanced computer code based on the finite volume approach. Examination of obtained results reveals that the rate of interaction between the free-surface and the wake structure downstream of the spherical body is maximum for the case of h/d=0.25 and by increasing the submerging elevation, the rate of this interaction decreases. At the submerging elevation of h/d=2.00, the free-surface effects are minimum and beyond h/d=2.00 it may be assumed that these free-surface effects on the sphere wake structure disappear.
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    Numerical investigation of flow structures around a sphere
    (TAYLOR & FRANCIS LTD, 2011) Hassanzadeh, Rahim; Sahin, Besir; Ozgoren, Muammer
    A numerical investigation of flow around a sphere is performed and compared with previous studies. Here, a second-order accurate, finite volume method is used in order to predict the instantaneous and time-averaged flow characteristics using large eddy simulation (LES) on the multi-block grid system. Namely, the objectives of this article are: (i) the presentation of flow structures in the wake region downstream of the sphere with a wide variety of flow properties such as the distribution of velocity vectors, patterns of streamlines, Reynolds stress correlations, root mean square of velocity components and other time-averaged flow data in order to reveal the vortical flow structures in detail and (ii) to demonstrate the abilities of computational methods in simulation of vortical flow data. Finally, it has been concluded that there are good agreements between the experimental results and numerical predictions.