Numerical predictions of heat transfer and fluid flow characteristics for seven different dimpled surfaces in a channel

Heat transfer and fluid flow characteristics for seven different dimpled surfaces on one surface of a channel are predicted numerically using version 6.1.18 of FLUENT. The turbulent model employed is a realizable K-E model without a wall function. The different dimples investigated are spherical dimples, tilted cylinder dimples, cylinder dimples, in-line triangular dimples, reverse in-line triangular dimples, staggered triangular dimples, and reverse staggered triangular dimples. Results show the existence of a centrally located vortex pair and vortex pairs near the spanwise edges of each dimple for the three circular dimple types, which augment local magnitudes of eddy diffusivity for momentum and eddy diffusivity for heat. Advection of reattaching and recirculating flows from locations within the spherical-type dimple cavities, as well as strong instantaneous secondary flows and mixing within the vortex pairs, are especially apparent. For the four triangular types of dimples, only one primary flow circulation zone generally is present within individual dimples. In all cases, regions of augmented streamwise vorticity show approximate correspondence to locations where eddy diffusivities for momentum and heat are increased Overall, the highest heat transfer augmentations, and the most significant local and overall increases to eddy diffasivity for momentum and eddy diffusivity for heat, are produced by the spherical dimples and the tilted cylinder dimples.