Numerical simulation of fluid flow and heat transfer in a curved square duct by using the lattice Boltzmann method

In this article, the three-dimensional 27-velocities (D3Q27) lattice Boltzmann method (LBM) is employed to simulate the fully developed fluid flow and heat transfer in a curved square duct with curvature ratio 0.05-1.0 and Dean number 0-200. The so-called Dean instability in the curved square duct is fully investigated. It is found that for the square duct with high curvature ratio, the onset of transition from single-pair vortex to double-pair vortex depends on both Dean number and curvature ratio. This is consistent with conventional computational fluid dynamic (CFD) and experimental results, and the differences between simulation and experiment are very small. For the friction coefficient and Nusselt number, which are functions of Dean number and curvature ratio, it is found that the numerical results are in good agreement not only with the available experimental correlation but also with conventional CFD results under the given conditions.