Thermo-fluids effects of a grooved circular cylinder in laminar flow regimes

The force coefficients and heat transfer related to a circular cylinder with grooved surfaces are studied at Re <= 200. Three types of grooved surfaces are examined: square, triangle, and dimple. The grooves are arranged at theta = 0 degrees, 30 degrees, 45 degrees, 60 degrees, 90 degrees from the forward stagnation point of the cylinder. It is shown that the existence of a groove controls the dynamic behavior of the vortices; as such lift and drag coefficients have been varied considerably, depending on the shape of the groove and theta. The coefficients appear very sensitive to triangle grooved surface, in particular, as theta varies to 45 degrees. The results reveal that triangle grooved surface could produce minimum drag coefficient when theta varies to 45(0) for all examined Re; this is found much lower than that of the square and dimple grooved surfaces and even smooth cylinder. A significant enhancement of the Nu is attained in the wake of the triangle grooved cylinder surface with the angle of the location of 450. At low Reynolds number (Re = 50), the Nu value of triangle grooved surface with theta = 0 degrees is shown higher than that of other grooved surfaces, whereas this value is found to the lowest at high Reynolds number (Re = 200).