مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

حل عددی جریان و انتقال حرارت در کانال حفره‌دار با استفاده از مدل‌های آشفتگی رینولدز پایین

نویسندگان
محمد فضلی 1
مهرداد رئیسی دهکردی 2
1 گروه مهندسی مکانیک، دانشکده مهندسی مکانیک، دانشگاه تهران، تهران، ایران
2 دانشگاه تهران
چکیده
در این مقاله به بررسی عملکرد سه مدل اغتشاشی k-ε ناحیه‌ای، k-ε رینولدز پایین خطی و k-ε رینولدز پایین غیرخطی در پیش-بینی جریان و انتقال حرارت داخل کانال حفره‌دار پرداخته شده است. همچنین اثر اعمال ترم NYP به جای ترم اصلاح مقیاس طول YAP مورد مطالعه قرار گرفته است. حفره‌ها تجهیزات انتقال حرارتی هستند که در پره‌های توربین گاز به کار می‌روند تا میزان انتقال حرارت را بالا ببرند. این تجهیزات بصورت مانعی در برابر جریان قرار نمی‌گیرند، بنابراین افت فشار زیادی را ایجاد نمی-کنند. در این پژوهش به منظور حل معادلات حاکم بر جریان و انرژی از روش حجم محدود به همراه الگوریتم سیمپل استفاده شده است. نتایج بدست آمده با ترم اصلاح YAP حاکی از آن است که مدل غیرخطی نسبت به مدل‌های ناحیه‌ای و خطی، جریان چرخشی بزرگتری را درون حفره پیش‌بینی می‌کند. همچنین شدت برخورد و جهش جریان در این مدل از دو مدل دیگر بیشتر است. با مشاهده نتایج انتقال حرارت درمی‌یابیم که مدل ناحیه‌ای، میزان انتقال حرارت را کمتر از نتایج تجربی بدست می‌آورد. با اعمال مدل خطی، نتایج بهتری از انتقال حرارت در داخل حفره و لبه عقبی آن ارائه می‌گردد. نسبت به این دو مدل، مدل غیرخطی هم در لبه عقبی حفره و هم در فضای صاف بین حفره‌ها پیش‌بینی بهتری را بدست می‌‌آورد. در مقایسه با نتایج بالا، اعمال ترم NYP به جای ترم YAP در مدل‌های خطی و غیرخطی، باعث ارائه نتایج دقیق‌تری از انتقال حرارت در راستای عرضی و لبه عقبی حفره می‌گردد.
کلیدواژه‌ها
کانال حفره‌دار
مدلسازی اغتشاش
مدل غیرخطی
انتقال حرارت

موضوعات

عنوان مقاله English

Computation of flow and heat transfer over dimpled channels using low-Reynolds number turbulence models

نویسندگان English

Mohammad Fazli 1
M. Raisee Dehkordi 2
1 School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
2 University of Tehran
چکیده English

In this paper, the performance of three turbulence models, zonal k-ε, linear low-Reynolds k-ε and nonlinear low-Reynolds k-ε in the prediction of flow and heat transfer through a dimpled channel is investigated. Furthermore, the effect of YAP term replacement with NYP length scale correction term is studied. Dimples are heat transfer devices which are employed in gas turbine blades to increase the heat transfer levels. These devices do not act as an obstacle for flow, and thus they produce low pressure losses. In this study, the governing equations on flow and energy are solved using the finite volume method together with the SIMPLE algorithm. The results obtained with YAP term indicate that the nonlinear model predicts larger recirculation flow inside the dimple than zonal and linear models. Also, the intensity of impingement and upwash flow in this model is greater than other models. Heat transfer results show that the zonal model predicts the heat transfer levels lower than experimental measurement. Using the linear model leads to a better prediction of heat transfer inside the dimples and their back rim. Compared to these models, the nonlinear model yields a better prediction not only for the smooth area between the dimples, but in the back rim of the dimple. The replacement of the YAP term with the NYP term in linear and nonlinear models leads to more accurate results for heat transfer in dimple span-wise direction and back rim.

کلیدواژه‌ها English

Dimpled channel
Turbulence Modeling
nonlinear model
Heat Transfer
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مهندسی مکانیک مدرس
دوره 18، شماره 5
شهریور 1397
صفحه 13-23