IJE TRANSACTIONS A: Basics Vol. 31, No. 1 (January 2018) 65-70   

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M. R. Ashory, F. Talebi and H. Roohi Ghadikolaei
( Received: November 23, 2016 – Accepted in Revised Form: November 30, 2017 )

Abstract    In this study, the stirring mechanism of shear-thinning fluids benefiting from four blades in turbulent flow is considered. The fluid is studied inside a stirred cylindrical tank with a flat bottom. The height of fluid is equal to the cylinder’s diameter and the impeller is positioned centrally. A CFD simulation has been carried out and three-dimensional turbulent flow is numerically analyzed using the Shear Stress Transport k-ω (k- ω SST) model. The parameters related to power consumption including attack angle and flow index were studied. The power consumed during the mixing of the shear thinning liquids under a specific Reynolds number and attack angle is less than that consumed when the fluid used is water, which is a Newtonian fluid. As the power law index decreases, the corresponding power consumption also declines. At a certain attack angle and power law index, an increase in the Reynolds number first significantly decreases power consumption; beyond a given range, the consumption plateaus. To validate the numerical simulation results, the findings derived on the basis of the power number used in this work were compared with the test results of other studies, and good agreement was observed.


Keywords    Turbulent flow, Power consumption, Mixing vessel, Shear thinning fluid, Blade attack angle


چکیده    در این مطالعه، سازوکار اختلاط سیال shear-thinning[ah1] توسط یک پروانه چهار پره­ای در رژیم جریان مغشوش، بررسی شده است. سیستم اختلاط متشکل از یک مخزن استوانه­ای با کف تخت است که تا ارتفاع معادل با قطر مخزن از سیال پر شده و پروانه در وسط مخزن قرار دارد. شبیه سازی جریان مغشوش با استفاده از مدل k- ω SST در تحلیل سه بعدی CFD انجام شده است. پارامترهای موثر بر توان مصرفی مخلوط­کن نظیر زاویه حمله و شاخص جریان (flow index) مورد مطالعه قرار گرفت. توان مصرفی در اختلاط سیال shear-thinning تحت یک عدد رینولدز و زاویه حمله خاص، کمتر از سیال نیوتنی آب می­باشد و هر چه شاخص عدد توان کاهش ­یابد، این توان مصرفی نیز کاهش می­یابد. همچنین، در یک زاویه حمله و شاخص عدد توان مشخص، افزایش عدد رینولدز ابتدا سبب کاهش قابل ملاحظه توان مصرفی شده و از یک محدوده­ای به بعد تاثیر چندانی در کاهش آن ندارد. به منظور صحه سنجی نتایج شبیه­سازی، عدد توان به دست آمده از این پژوهش با نتایج مقاله­ای دیگر مقایسه شد و انطباق خوبی بین آنها مشاهده شد.


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