Computational Modelling of the Flow and Heat Transfer in Dimpled Channels

The flow and heat transfer characteristics over a single dimple and an array of staggered dimples have been investigated using the Reynolds Averaged Navier-Stokes (RANS) approach. The objective is to determine how reliably RANS models can predict this type of complex cooling flows. Three classes of low-Reynolds number RANS models have been employed to represent the turbulence. These included a linear eddy viscosity model (EVM), a non-linear model (NLEVM) and a Reynolds Stress transport model (RSM). Variants of the k-epsilon model have been used to represent the first two categories. Steady and time-dependent simulations
have been carried out at a bulk Reynolds number of around 5000 with dimple print diameter to channel height ratios of D=H = 1:0; 2:0 and ratios of dimple depth to channel height of dhelta=H = 0:2; 0:4. The linear EVM and the RSM tested both produce symmetric circulations in the dimples, while the NLEVM produces an asymmetric pattern. The mean velocity profiles predicted numerically are generally in good agreement with the data. The main flow characteristics are reproduced by the RANS models, but some predictive deviations from available data point to the need for further investigations. All models report an overall enhancement in heat transfer levels when using dimples in comparison to those of a plane channel.