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Numerical simulation of mixed convection flow of nanofluids in a lid-driven cavity
The thermal conductivity of nanofluids is greatly influenced by the nanoparticles and base fluid characteristics which was first observed and modeled by Maxwell. In this study an improved model given by Patel which predicts the thermal conductivity over a wide range of particle size and concentration was implemented. A mixed convection flow in a lid-driven cavity was simulated using cupric oxide (CuO) and water based nanofluids. Natural convection was induced by the temperature difference between the vertical walls with the horizontal walls being insulated. Forced convection was introduced by no-slip moving top wall.
The three-dimensional, VOF-Navier-Stokes(VOF-NS) solver developed during Bachelor thesis was used for the simulations. Boussinesq approximation was used to account for the buoyancy effect caused by the temperature difference. In addition, a two-dimensional Lattice Boltzmann (LBM) solver was used for the comparative study. LBM solver used a D2Q9 model with Bhatnagar-Gross-Krook (BGK) approximation to model the collision term.
The results obtained by varying Reynolds number, Rayleigh number and solid volume fractions using VOF-NS solver and LBM solver was compared with the mixture model using the commercial package ANSYS (FLUENT)15. The effect of variation of these parameters on hydrodynamic and heat transfer characteristics were studied.
Schematic of the test case
Comparison of the results from LBM solver and Ansys Fluent @ Ra=1.47E5; Re=10; Vol fraction = 5% .
Temperature contour plot and streamline plot of velocity vector using LBM solver.
Temperature contour plots form VOF-NS solver for with and without nanoparticles, plotted at 500th second (physical time) on a 80*80*1 domain. ; Volume fraction=1% ; Ra Nu= 1.45E5 ; Solid line – nanofluid ; Dashed line - basefluid
Streamline plots of the velocity vector at 500th second from VOF-NS solver. ; Volume fraction = 1%.
Velocity magnitude contour plots with and without nanoparticles at 500th second from VOF-NS solver. ; Volume fraction = 1% ; Solid line – nanofluid ; Dashed line - basefluid.