Results 4, Roll Structure, Close-Up

In order to know more closely the three-dimensional structure of the aforementioned roll structure shown in Fig. 4, we plot a close-up view of the three dimensional vorticity and velocity fields (Fig. 5). The anticyclonic blue roll is accompanied by the approximately circular rotation of the fluid around the center of the roll. The associated streamlines (not shown) tilt slightly from a vertical plane, resulting in the anticyclonic circulation in the vertical direction. For the cyclonic red vortex, the horizontal rotation associated with the vertical vorticity is more prominent than for the anticyclonic roll. Such difference between the anticyclonic and cyclonic rotations are likely to be related with the difference in length between the anticyclonic rolls and cyclonic ovals shown in Fig. 4.

Figure 5. Three dimensional close-up view of vorticity (blue and red colored surface) and velocity (green cones) fields for a roll, with a oval at the back. As in Fig. 4, the surfaces of an amplitude of 2.5*10^-4s^-1 for the three-dimensional vorticity are visualized, and red (blue) color indicates that the vertical component of the vorticity is positive (negative). The maximal three-dimensional velocity in the visualized domain is 0.077 ms^-1.