Effects of Cylinder Diameters, Reynolds Number and Distance Between Two-Tandem Cylinders on the Wake Profile and Turbulence Intensity

Abstract

A series of experimental and numerical investigations on two tandem cylinders wake have been studied. The velocity profile and turbulence intensity have been acquired by a single one dimensional Hot Wire anemometer. The two cylinders were mounted in a tandem manner in the horizontal mid plane of the working section. The effect of the upstream cylinder diameter, Reynolds number and the distance between the cylinders on the wake profile and turbulence intensity on the downstream cylinder was investigated, while the Reynolds number ranged between 1.5× ⟦10⟧ ^4 ∼ 3× ⟦10⟧ ^4. The upstream cylinder diameter (d) was 10, 20 and 25 mm, while the downstream cylinder diameter (D) was 25 mm, corresponding to d/D ranging from 0.4 ∼1.0. The spacing ratio L/d (where L is the distance between the upstream cylinder center and the leading stagnation point of the downstream cylinder) was 2 and 5.5, covering different flow regimes. Observations indicate that two symmetric turbulence intensity peak will occur at mean velocity gradient area. Turbulence area will increase in width for both L/d = 2 and 5.5 as increasing distance from the cylinder (x/D) and decreasing free stream velocity. But totally the range of the turbulence area for L/d = 5.5 is greater than L/d = 2. The wake profiles show that the velocity defect increases as increasing upstream cylinder’s diameter for L/d = 5.5. While this order cannot be accessed for L/d = 2. It is observed that sudden and unusual velocity defect happened for L/d = 2 and d/D = 0.8 cases, which means that the most velocity defect is running on. Also, numerical solution results of velocity profile have been compared with the mentioned experimental results at station 4 and velocity of 10 m/s for both L/d = 2 and 5.5. Results shows a little difference because of using one-dimensional Hot-wire.