OCR Text |
Show Radial distributions of aZimuthal velocity are shown in Fig. S. For X/Of =-0.15 and outside the bluff body r/Df =0.12, azimuthal velocity profile is of a Rankine vortex type, with maximum value at r/Df =0.15. As the expansion of the swirling air exit the quarl, maximum values of azimuthal velocity decrease. The magnitudes and positions of the maximum azimuthal velocities are not very diffe~ent within the furnace, which has a value W/Uo=1.5 at position of r/Df~ 0.1., ' and their profiles are similar in shape. The profile is · typical of a Rankine vortex, whcih combine a force vortex in the core region, r/Df~0:1, and a free vortex outside the core. Along the centerline, azimuthal velocities go to zero. From Fig.4, it is observed that, at most locations along the centerline, . Wrms is greater than Urms . Examination of radial profiles of Wrms is greater than Urms . Examination of radial profiles of Wrms reveal that this results occur only near the centerline. In most of the region besides centerline, the turbulence filds achieve similar rms values for azimuthal and axial velocities and flat profiles revealed. The swirl flow seems to be responsible for this nearly isotropic velocity fluctuation. The reverse mass-flow rate in an axial direction at any section of the recirculation zone is given by Mr= J r u2 211: P unrdr (1 ) rUl where r u1 and r u2 are the radial positions of the zero mean velocity, and un is the nagative mean axial velocity. The axial distributions of the normalized reverse mass flow rate (Mr/Mo) are show in Fig.6, where Mo is the initial mass |