Numerical Study of Turbulent Air Flow through the 180 Degree Oscillating Circular- Sectioned Bend

The unsteady developing turbulent air flow, through oscillating circular-sectioned curved pipe with the angle of 180° was investigated numerically. The bend had a diameter of 106 mm and a curvature radius ratio of 6.0 with long, straight upstream and downstream tubes. Results of the mean velocity and static pressure were obtained at a Reynolds number of 31200 and at various longitudinal stations. The velocity of the primary flow was illustrated in the form of contour map. In the inlet plane of the bend, the pressure gradient increases along the outer wall and decreases along the inner wall. Therefore, the fluid near the inner wall is accelerated and that near the outer wall is decelerated. In this bend the elliptic curves of velocity contour were observed from φ=120° to φ=150°. In these portions, the faster fluid near the inner wall was moved by the secondary flow towards the outer wall through the central region of the cross section. In the outlet plane, the fluid transported to the outer wall, was carried towards the inner wall by the secondary flow moving inwards along the wall.

Keywords:

Air flow , Curved pipe , Oscillation , Turbulent