Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 6
    Asymmetric Y-Shaped Micromixers With Spherical Mixing Chamber for Enhanced Mixing Efficiency and Reduced Flow Impedance
    (Isfahan University of Technology, 2021) Çetkin, Erdal; Miguel, A. F.
    Microfluidic devices have many attractive qualities such as low cost, small size, and in-field use. Micromixers are very important components of these devices because affect their efficiency. In a passive mixer, the structural characteristics of the mixer are crucial and must be analyzed. This paper presents a numerical study of the mixing in passive Y-shaped micromixers with a spherical mixing chamber for a volume constrained system. The effect of asymmetric bifurcated ducts, the angle in between the inflow ducts, eccentricity and, obstacles inserted in the mixing sphere, on the mixing efficiency and flow impedance is evaluated. Vortical structures characteristics and the possible occurrence of engulfment are also identified. The results show that flow impedance (pressure drop for unit volumetric flow rate) can be decreased greatly for the same mixing efficiency as the volume of the spherical mixing chamber is 20% of the total volume. Insertion of the obstacles into the sphere mixing chamber decreases the mixing efficiency while they increase the flow impedance. The results also show that spherical mixing chamber enhances mixing efficiency while decreasing flow impedance if the volume reserved for it is greater than a limit value which depends on the diameter and length scale ratios in between the mother and daughter ducts as well as the total volume. Overall, the paper documents the variation of mixing efficiency and flow impedance based on the geometrical parameters of three-dimensional asymmetric passive micromixer with sphere mixing chamber.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Observational and Numerical Methods for Quantifying and Modeling of Turbulence in a Stratified Reservoir
    (Isfahan University of Technology, 2016) Elçi, Şebnem; Ekmekçi, Hüseyin Burak
    The interplay between stratification and shear in lakes controls the vertical mixing, which is the mostimportant mechanism affecting the transport of heat, salt, momentum and suspended and dissolvedsubstances. This study attempts to quantify and characterize the turbulence from direct measurementsconducted in a reservoir. A 3D numerical model is used to investigate the water column hydrodynamics forthe duration of measurements and the performance of various turbulence models used in the CFD model areinvestigated via simulation of mixing in the reservoir. The drawdown curves produced by the turbulencemodels are formulized through linear equations. Although, use of different turbulence models do not havesignificant effects on the flow hydrodynamics away from the intake structure; significant effects especially onturbulence kinetic energy production are observed at the orifice. Therefore, for simulation of withdrawalflow, either use of shear stress transport (SST) k-omega models solving equations all the way to the wall or kepsilonmodels with the nonequilibrium wall function is recommended to account for the changes in thepressure gradient. In this study, the methods using quantified turbulent characteristics of the flow toreformulate the Stokes' settling velocity to be applied in turbulent flows are also investigated. An approach topredict setting velocity in turbulent flows that utilizes acoustic Doppler instruments for quantification ofturbulent characteristics is presented. Modification of the Stokes' settling velocity with thenondimensionalized turbulent kinetic energy production profiles lead better results than other turbulencecharacteristics (buoyancy flux and by Richardson number flux) widely used in characterizing turbulentmixing.