Investigação numérica da convecção natural de fluidos de lei de potência em cavidade aberta quadrada e preenchida com meio heterogêneo

Abstract

In recent years non-newtonian fluids have been receiving increasing attention for their use in industries. This work dedicates itself to studying the behaviour of natural convection of a generalized newtonian fluid in a cavity filled with heterogeneous medium and open to a reservoir. The horizontal walls of the cavity are adiabatic and the vertical wall is heated. The cavity is of square dimensions and filled with blocks forming an heterogeneous medium of porosity φ = 0; 64. Fluid follows the power-law model and has a fixed Prandtl number P r = 1000 and power-law inex n varying from 0; 6 to 1; 4. Fluid flow occurs in a steady-state and is caracterized by the Rayleigh number, which is varied from 104 a 107. The numerical solution is executed by commercial fluid dynamics software ANSYS FLUENT R through the finite volume method. Pressure-velocity coupling is accomplished through the SIMPLE method and the discretization for the advective terms through the QUICK algorithm. Solution verification is made by comparison with published works for the open cavity and an enclosure with a centered block utilizing newtonian fluid, and for an enclosure with power-law fluid. Adequate meshing of the domain is obtained and applied to all cases solved, with results presented in the form of plots for Nusselt number on the heated wall and nondimensional mass flow through the cavity opening. Streamlines, heatlines, temperature and velocity profiles, and viscous fields are also observed. Results obtained show a strong dependence of the convection to changes on the varied parameters. In general, natural convection tends to increase with Rayleigh number or through the reduction of the power-law index. Increasing the number of blocks affects convection negatively through the boundary-layer interference phenomenon, which can be predicted by an approximation provided.