Heat transfer enhancement of three dimensional shear flow near a wall

A numerical study on the wake behind a cornerstone placed parallel to a wall has been made and compare with square cylinder. In recent study others work on a cylinder placed parallel to a wall. The cornerstone is considered to be within the boundary layer of the wall, so that the outside flow is taken to be due to uniform shear. Flow has been investigated in the laminar Reynolds number (based on the cord of cornerstone) range. The interaction of wall boundary layer on the vortex shedding at Reynolds number up to 1400.0 has been investigated for cornerstone to wall gap height 0.25, 0.5, 0.75 and 1.0 times the cord of cornerstone. In this study, three-dimensional (3D), unsteady and incompressible Navier-Stokes equations are solved. k-ω(SST) and k-ε(RNG) models have been used to compute these equations. Flow visualizations along with turbulence statics are presented to gain insight into the flow structures that are due to interaction between the shear layers and the approaching boundary layer. Vortex shedding suppression occurs and wake becomes steady up to a certain value of Reynolds number at gap height 0.25 time the cord of the cornerstone and a primary bubble formed. At higher Reynolds number the formation of a single row of negative vortices behind the cornerstone when it is in close proximity to wall is noteworthy. Due to the shear, the drag experienced by the cornerstone is found to decrease with the reduction of gap height .we see that k-ω(SST) can find vortex shedding better than k-ε(RNG) model. Heat transfer coefficient is analyzed in this study. We find that after passing the cornerstone, heat transfer coefficient in (G/D=0.25) increases because of formation of primary bubble.

کلیدواژه ها:

cornerstone ، vortex shedding ، primary bubble ، gap ratio