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Article
Numerical study of the mixed convection flow over a square cylinder

Author: Sajida Lafta Ghashim Jassim ساجدة لفتة
Journal: Iraqi Journal of Chemical and Petroleum Engineering المجلة العراقية للهندسة الكيمياوية وهندسة النفط ISSN: 19974884/E26180707 Year: 2010 Volume: 11 Issue: 1 Pages: 29-45
Publisher: Baghdad University جامعة بغداد

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Abstract

In this work, a numerical study is performed to predict the solution of two – dimensional, steady and laminar mixed convection flow over a square cylinder placed symmetrically in a vertical parallel plate. A finite difference method is employed to solve the governing differential equations, continuity, momentum, and energy equation balances. The solution is obtained for stream function, vorticity and temperature as dependent variables by iterative technique known as successive over relaxation. The flow and temperature patterns are obtained for Reynolds number and Grashof number at (Re= -50,50,100,-100) (positive or negative value refers to aidding or opposing buoyancy , +1 assisting flow, -1 opposing flow) and (102 to 105) , respectively. The results displaced that the recirculation length above the cylinder increases with the increase in Gr number and the average Nu number is the highest at the lower surface of the cylinder, while is the lowest at the top of the cylinder surface. A comparison between the obtained results and the published computational studies has been made and it showed a good agreement.


Article
Numerical Analysis of Laminar Natural Convection in Square Enclosure with and without Partitions and Study Effect of pPartition on the Flow Pattern and Heat Transfer

Author: Sajida Lafta Ghashim Jassim ساجدة لفتة
Journal: Iraqi Journal of Chemical and Petroleum Engineering المجلة العراقية للهندسة الكيمياوية وهندسة النفط ISSN: 19974884/E26180707 Year: 2012 Volume: 13 Issue: 1 Pages: 33-54
Publisher: Baghdad University جامعة بغداد

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Abstract

The problem of steady, laminar, natural convective flow in an square enclosure with and without partitions is considered for Rayleigh number (103-106) and Prandtl number (0.7). Vertical walls were maintained isothermal at different temperatures while horizontal walls and the partitions were insulated. The length of partition was taken constant. The number of partitions were placed on horizontal surface in staggered arrangement from (1– 3) and ratio of partition thickness (H/L= 0.033, 0.083, 0.124). The problem is formulated in terms of the vorticity-stream function procedure. A numerical solution based on a program in Fortran 90 with the finite difference method is obtained. Representative results illustrating the effects of the thickness and number of partitions on the contour maps of the streamlines and temperature are reported and discussed. In addition, the local Nusselt number is evaluated. Results show that the values of stream function (the strength of flow) in enclosure increases with the increasing Rayleigh number. As the number of partitions and thickness of partition increases, the strength of flow decreases. Mean Nusselt number increases with increasing Rayleigh number at different number of partitions. The numerical results are compared with available numerical results and experimental data and a good agreement is obtained.

يتضمن البحث الحالي دراسة نظرية عددية لانتقال الحرارة بالحمل الحر للجريان المستقر داخل حيز مربع بوجود او عدم وجود الحواجز.الدراسة تغطي المدى لرقم رايلي من103 الى 106 ولعدد برانتل ((Pr=0.7.الجدران العمودية للحيز ذات درجات حرارة ثابتة لكن مختلفة بينما الجدران الافقية معزولة. ارتفاع الحواجز الموضوعة داخل الحيز ثابت وموضوعة على الجدران الافقية بترتيب متخالف وباعداد مختلفة تتراوح من( 1- 3 ) وسمك الحواجز المسخدم تساوي(H/L=0.033, 0.083, 0.124) . الحل العددي تم باستخدام طريقة دالة الانسياب- الدوامّية بأستخدام طريقة الفروق المحددة مع بناء برنامج حاسوبي بلغة(فورتران 90). تم دراسة تاثير كل من رقم رايلي ، عدد الحواجز ، وسمك الحواجز على شدة الدوامات الدوارة و انتقال الحرارة داخل الحيز . بالاضافة الى ذلك تم ايجاد معدل قيم رقم نسلت. بينت النتائج ان شدة الدوامات الدوارة تزداد مع زيادة عدد رايلي بينما تقل عند زيادة عدد الحواجزاو سمك الحواجز . كذلك بينت النتائج ان متوسط نسلت يزداد مع زيادة رقم رايلي. وتم مقارنة النتائج العددية مع النتائج العددية والعملية المتوفرة وكانت نتائج المقارنة جيدة.

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