Emirates Journal for Engineering Research, 18 (2), 53-61 (2013) (Regular Paper) 53 DEPENDENCE OF BUOYANCY-DRIVEN FLOW INSIDE AN OBLIQUE POROUS CAVITY ON ITS ORIENTATION Iman Zahmatkesh Department of Mechanical Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran E-mail address: zahmatkesh5310@mshdiau.ac.ir (Received February 2013 and Accepted June 2013) اهﺘﻤﺎم هﺬﻩ اﻟﻮرﻗﺔ ﻳ ﺗ آﻴﻔﻴﺔ ﺗﻮﺿﻴﺢ ﻋﻠﻰ ﺘﺮآﺰ ﺄ ﺛ ﻴ اﺗﺠ ﺮ ﺎ ﻩ ﻣﻴﻞ ﻣ ﻣﺴﺎﻣﻲ ﺗﺠﻮﻳﻒ ﺎﺋﻞ ﻋﻠﻰ ﺗﻄﻮر ﺣﺮآ ﻲ ﻟ اﻟﻄﻔﻮ ﺘﺪﻓﻖ ﻓﻴﻪ. ﻟﻘﺪ و ﺗﻢ وﺿﻊ ﺟﺪار ﻳ ﻦ ﻣ ﺘ ﻘﺎﺑﻠ ﻴﻦ وﻟﻜﻦ ﺛﺎﺑﺘﺔ ﺣﺮارة درﺟﺎت ﻓﻲ ﻟﺘﺠﻮﻳﻒ ﻗﻴﻢ ﻋﻨﺪ ﺗﻢ ﺣﻴﻦ ﻓﻲ ﻣﺨﺘﻠﻔﺔ ﻋﺰل اﻟﺠﺪارﻳﻦ اﻵﺧﺮ ﻳ ﻦ. ﺗﻢ وﻟﻘﺪ ﺣﻞ ﺣﻔﻆ ﻣﻌﺎدﻻت ﻋﺪدﻳﺎ واﻟﻄﺎﻗﺔ اﻟﺪاﻓﻌﺔ، واﻟﻘﻮة اﻟﻜﺘﻠﺔ، ﺑ ﺎ ﻻ ﻋﺘﻤﺎد ﻋﻠﻰ اﻟﻌﻤﻠﻴ ﺎت اﻟﺤﺴﺎﺑﻴﺔ اﻟﻤﺴﺘﻨﺪة ﻋ ﻠﻰ ﺗﺤﻜﻢ ﻋﻨﺼﺮ اﻟ ﺤﺠﻢ. و ﻣ ﺗﻢ ﻨﺎﻗﺸ ﺔ ﺗﻜﻮن اﻻﻃﺮاب) اﻻﻧﺘﺮوﺑﻲ( ﺗﺄﺛﻴﺮ ﺗﺤﺖ ﻧﻘﻞ اﻟﺤﺮارة ﻣﺮﺗﺠﻌﺔ اﻟﻐﻴﺮ ﺗﺄﺛﻴﺮ ﺗﺤﺖ و اﺣﺘﻜﺎك اﻟﺴﻮاﺋﻞ ﻣﺮﺗﺠﻊ اﻟﻐﻴﺮ. و ﻧﻤﻮذج ﺻﺤﺔ ﻣﻦ اﻟﺘﺤﻘﻖ ﺗﻢ اﻟ اﻟﺤﻞ ﻌﺪدي ﺑ ﺑﺎﻟﻤﻘﺎرﻧﺔ ﺳﺎﺑﻘﺎ ﻣﻨﺸﻮرة ﺄﻋﻤﺎل. و ﻋﺮض ﺗﻢ ذﻟﻚ، ﺑﻌﺪ و ﻣﻘﺎرﻧﺔ ﻧﺘﺎﺋﺞ اﻟﻤﺤﺎآﺎة اﻟﻌﺪدﻳﺔ ﻟﺰواﻳﺎ اﺗﺠﺎﻩ ﻣﻦ اﻟﻤﻴﻞπ/4 ، 3π/4 ، 5π/4 ، وπ/4 7 . اﻷ ﺑﻴﻦ ﻣﻦ أن وﺗﺒﻴﻦ اﻟﻤﻌﺮوﺿﺔ ﻣﺜﻠﺔ، أن ﺣﺎﻟﺔ أﻓﻀﻞ اﻻﻃﺮاب ﻟﺘﻜﻮن و اﻟﺤﺮارة ﻻﻧﺘﻘﺎل) اﻻﻧﺘﺮوﺑﻲ( ﺗﺘﺤﻘﻖ ﺧﻼل ﻣﻦ اﺗﺠ ﺎ ه ﻣﻴﻞ ﺎت ﻓﻴﻬﺎ ﻳﻜﻮن اﻟﺠﺪار اﻟﺴﻔﻠﻲ اﻟﺠﺰء ﻓﻲ اﻟﺒﺎرد واﻟﺠﺪار اﻟﻌﻠﻮي اﻟﺠﺰء ﻓﻲ اﻟﺴﺎﺧﻨﺔ. In the present paper attention is focused to clarify how orientation of an oblique porous cavity may affect the establishment of buoyancy-driven flow therein. Two opposite walls of the cavity are kept at constant but different temperatures while the other two are maintained adiabatic. The mass, momentum, and energy conservation equations are solved numerically adopting a control- volume based computational procedure. The generation of entropy is also discussed taking into account both heat transfer irreversibility and fluid friction irreversibility. The developed numerical model is validated against previously published works. Thereafter, simulation results are presented for the inclination angles of π/4, 3π/4, 5π/4, and 7π/4 and the corresponding results are compared. It is demonstrated that, among current cases, the optimum case with respect to heat transfer as well as entropy generation is achieved through the orientations with the hot wall in the top and the cold wall in the bottom. 1. INTRODUCTION Buoyancy-driven flows inside cavities filled with a fluid-saturated porous medium appear in diverse practical situations including cooling of radioactive waste containers, grain storage, terrestrial heat flow through aquifer, and heat exchange in granular insulating materials. Consequently, it is not surprising to see considerable interest in the analysis of these flow problems in the past (e.g., Baytas and Pop [1], Saeid and Pop [2], Misirlioglu et al. [3], and Zahmatkesh [4,5]). A porous cavity can be oblique or vertical depending on its orientation with respect to gravity. Thereby, some previous attention has been paid to buoyancy- driven flows inside oblique porous cavities. One of the first contributions has been made by Moya et al. [6] who analyzed the consequences of inclination angle on the induced flow and thermal fields inside porous cavities. Free convection in oblique porous cavities with partially cooled walls has been investigated by Oztop [7]. He found that inclination angle is the dominant parameter on heat transfer and fluid flow as well as aspect ratio. The effect of inclination angle has also been examined during numerical simulations of Dawood and Ismaeel [8]. Baytas [9] has studied free convection and entropy generation inside oblique porous cavities. He clarified how inclination angle may affect the distributions of streamlines, isothermal lines, and iso-entropy generation lines. Moreover, he presented the variations of local Nusselt number and global entropy generation rate with the inclination angle. More recently, control of free convection and entropy generation in oblique porous cavities by placing of a partition has been discussed by Heidary et al. [10]. In all of the aforesaid studies, free convection was the sole heat transfer mode that was taken into account. Nevertheless, investigations of Zahmatkesh [11] and Badruddin et al. [12] have demonstrated that, thermal radiation may possess profound consequences on the establishment of the flow and thermal fields inside porous cavities. It makes temperature distribution nearly uniform in vertical sections inside the cavity