laminar mixed convection of cu-water nano-fluid in two- sided lid-driven enclosures

the fluid flow and heat transfer in lid-driven enclosures filled with cu-water nanofluid is numerically investigated. the moving vertical walls of the enclosure  are maintained in a constant temperature, while the horizontal walls are insulated. the hybrid scheme is used to discretize the convection terms and simpler algorithm is adopted to couple the velocity field and pressure in the momentum equations. the effect of moving direction of walls on mixed convection is studied for various ri numbers, aspect ratios and volume fractions of nanoparticles. for this purpose, vertical walls are moved in two directions: one, force convection aids to free convection and two, it interacts to free convection. it is observed that the direction of moving wall mainly affected the flow field, temperature gradient and heat transfer. in addition, by increasing the volume fraction of  nanoparticles, the variation of average nusselt number on the hot wall, as an index of heat transfer   rate, is linear in two cases.