Flow simulation in a complex fluidics using three turbulence models and unstructured grids

Purpose - The purpose of this paper is to simulate the behaviour of the symmetrical turn-up vortex amplifier (STuVA) to obtain insight into its maximum through-flow operation within the eight-port STuVA, and understand the relation between its design parameters and flow characteristics. Furthermore, it is to test the performance of different turbulent models and near-wall models using the same grid, the same numerical methods and the same computational fluid dynamics code under multiple impingement conditions. Design/methodology/approach - Three turbulence models, the standard k-", the renormalization group (RNG) k-" model and the Reynolds stress model (RSM), and three near-wall models have been used to simulate the confined incompressible turbulent flow in an eight-port STuVA using unstructured meshes. The STuVA is a special symmetrical design of turn-up vortex amplifier, and the simulation focused on its extreme operation in the maximum flow state with no swirling. The predictions were compared with basic pressure-drop flow rate measurements made using air at ambient conditions. The effect of different combinations of turbulence and near-wall models was evaluated. Findings - The RSM gave predictions slightly closer to the experimental data than the other models, although the RNG k-" model predicted nearly as accurately as the RSM. They both improved errors by about 3 per cent compared to the standard k-" model but took a long time for convergence. The modelling of complex flows depends not only on the turbulence model but also on the near-wall treatments and computational economy. In this study a good combination was the RSM, the two layer wall model and the higher order discretization scheme, which improved accuracy by more than 10 per cent compared to the standard k-" model, the standard wall function and first order upwind. Research limitation/implications - The results of this paper are valid for the global pressure drop flow rate. It should be desirable to compare some local information with the experiment. Originality/value - This paper provides insight into the maximum through-flow operation within the eight-port STuVA to understand the relation between its design parameters and flow characteristics and study the performance of turbulence and near wall models.