Heat Transfer Research 45(7), 677–700 (2014) 1064-2285/14/$35.00 © 2014 by Begell House, Inc. 677 1. INTRODUCTION Mixed convection is a kind of convection including both natural and forced convec- tion. Its significant role in many applications in industry and engineering has been specified: lake and reservoirs (Imberger and Hamblin, 1982), food processing, crystal growth (Moallemi and Jang, 1992), electronic cooling devices, drying technologies, NUMERICAL SIMULATION OF MIXED CONVECTION IN A SiO 2 /WATER NANOFLUID IN A TWO–SIDED LID-DRIVEN SQUARE ENCLOSURE WITH SINUSOIDAL BOUNDARY CONDITIONS ON THE WALL Mohammad Hemmat Esfe, * Seyed Sadegh Mirtalebi Esforjani, Mohammad Akbari, & Mohammad Hadi Hajmohammad Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran * Address all correspondence to Mohammad Hemmat Esfe E-mail: M.hemmatesfe@gmail.com To investigate mixed convection flows through a nanofluid in a square double lid-driven cavity with various inclination angles and sinusoidal heating on the lef wall, a numerical method based on the finite volume approach is applied. In this work, a SiO 2 –water nanofluid was used. The cavity is nonuniformly heated from the lef, T h , and cooled from the opposite wall. The top and the botom moving walls were supposed to be insulated. The study was performed at the Richardson number from 0.1 to 10, Reynolds number from 1 to 100, and the solid volume fraction of nanoparticles φ altereing from 0 to 0.06. The effects of variations of Richardson and Reynolds number, angle of incli- nation, and solid volume fraction of nanoparticles on the hydrodynamic and thermal characteristics have been studied and discussed. As a result, it was found that the increases heat transfer rate with the solid volume fraction for a particular Re. The heat transfer rate also increases with the Rich- ardson and Reynolds numbers for a particular volume fraction. The problem of mixed convection flows through a nanofluid in a square double lid-driven cavity with various inclination angles and sinusoidal temperature profiles on the lef wall has not been reported so far. The effects of an increase in the shear force or buoyancy force, with another force kept constant, on heat transfer enhancement are studied. KEY WORDS: mixed convection, double lid-driven, numerical simulation, nanofluid