International Journal of Thermal Sciences 46 (2007) 970–979 www.elsevier.com/locate/ijts Numerical simulation of opposing mixed convection in differentially heated square enclosure with partition S.K. Mahapatra a,∗ , Anjan Sarkar b , A. Sarkar b a National Institute of Technology, Rourkela, Orissa 769008, India b Jadavpur University, Kolkata-32, West Bengal, India Received 3 November 2005; received in revised form 13 November 2006; accepted 13 November 2006 Available online 16 January 2007 Abstract In the present study, opposing mixed convection in a differentially heated partitioned enclosure is investigated. The Richardson number (Ri) has been varied to simulate mixed convection (Ri = 1) and forced convection dominated flow (Ri = 0.1). Comparison is also made with natural convection in order to establish clarity in understanding the physics. The phenomenon inside the enclosure with centrally located partitions and offset partitions are also analyzed through isotherm pattern and streamline pattern and shielding effect of such partitions has been critically examined. It is found that when height of centrally located partition increases beyond a certain height of 0.3H , the heat transfer in case of opposing mixed convection is found to be more than that of natural convection for a partitioned enclosure.  2006 Elsevier Masson SAS. All rights reserved. Keywords: Mixed convection; Partitioned enclosure; Rayleigh number; Richardson number 1. Introduction Mixed convection problem has got its extensive applications in the field of engineering, for example cooling of electronic de- vices, furnaces, lubrication technologies, chemical processing equipment, drying technologies etc. Analysis of above phenom- ena incorporating the partitions, extends its usability to various other practical situations such as wooden partitions in an air- conditioned room, the plastic coated partitions in a refrigerator, a card or any projections on a motherboard of a computer etc. Also, various instruments provided for intrusive measurements inside practical systems can be simulated as insulated parti- tions. In this paper the shielding effect of such projections in the form of partitions along with movement of isothermal walls on energy transfer has been thoroughly examined and discussed. Mixed convection within enclosures can be categorized as buoyancy aiding and buoyancy opposing flow. In the first case, it can easily be conceived that the natural convection loop be- * Corresponding author. E-mail addresses: swarupkumar_m@yahoo.com (S.K. Mahapatra), anjansirkar@yahoo.com (A. Sarkar). comes stronger forming a single loop inside the enclosure while in the later case, shear flow induced by the motion of wall op- poses the buoyancy driven flow and makes the phenomenon more complex. Considering the complexity of phenomenon in- side a partitioned enclosure with moving walls, a brief review of the relevant literature has been hereby presented. Arpaci and Larsen [1] have presented an analytical treatment of the mixed convection heat transfer in tall cavities having one moving isothermal vertical wall at a temperature differ- ent from the other wall while horizontal walls are kept adia- batic. They showed that in this particular case, the forced and buoyancy driven parts of the problem could be solved sepa- rately and combined to obtain the general mixed convection problem. Aydin [2] studied numerically and revealed the mech- anisms of aiding and opposing forces in a combined shear and buoyancy driven cavity. The phenomenon inside square enclo- sure was analyzed with moving vertical hot wall, either up- wards or downwards while keeping the opposite cold wall fixed. In their work, a parametric study was carried out by varying Gr/Re 2 from 0.01 to 100 with Pr = 0.71 and three kinds of heat transfer regimes were identified. Further it was pointed out that the range of Gr/Re 2 for opposing mixed convection was 1290-0729/$ – see front matter  2006 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ijthermalsci.2006.11.017