Flow and spreading behaviors of coaxial jets wake

Tóm tắt

Flow and spreading behaviors of swirling jets using a dual-blockage disk are studied experimentally. The control and blockage disks are placed concentrically in tandem. The smoke flow patterns are obtained using the flow visualization technique. The axial velocity and turbulence intensity are detected using a 1-D hot-wire sensor. The jet spreading characteristics are illustrated by using an Edge Detection Method. Two pairs of lung-formed vortices and triangle-formed vortices are induced in downstream wake at Rec ≤ 200. Two vortices are found near the field at 200 < Rec < 700, while no toroidal structure was found above the reflected jet at Rec ≥ 700. The recirculation bubble length was increased with increasing Rec until Rec < 700. The axial velocity and turbulence intensity at 200 < Rec < 700 are significantly greater than those in other modes. At Rec ≥ 700, the shear-layer vortices are found far away from the control disk.