24
P. Liu
Fig. 1.26 Tornado
Fig. 1.27 Vortex
development of spatial concentrated vortices. It is not difficult to understand
if it is the tail vortex of an airplane, because the root cause of vortex production is the motion of the airplane. But if there is no aircraft, it cannot be
produced in ideal fluid flow and uniform flow field. However, when shear and
convection occur in viscous fluids, there is no such conclusion. In fact, if wind
shear occurs, there will be vortices. The question is whether these vortices
can be concentrated, and if they can be concentrated, will they develop very
strongly. Whether the distributed vorticity can be centralized depends on
the angle between the direction of convective velocity and vorticity. If the
direction of convective velocity is almost parallel to the vector direction of
vorticity, it is possible for the vorticity flow to be combined by winding. If
the velocity in the axis region is very high, the vorticity will become more and
more concentrated, and eventually, the area of the vortex tube will become
smaller. So did the cyclone. Tornadoes usually stand on top of the sky. Why?
This is because in the horizontal convective wind shear zone (which can be
either in the air or near the ground), there will be a region with small vorticity
P. Liu
Fig. 1.26 Tornado
Fig. 1.27 Vortex
development of spatial concentrated vortices. It is not difficult to understand
if it is the tail vortex of an airplane, because the root cause of vortex production is the motion of the airplane. But if there is no aircraft, it cannot be
produced in ideal fluid flow and uniform flow field. However, when shear and
convection occur in viscous fluids, there is no such conclusion. In fact, if wind
shear occurs, there will be vortices. The question is whether these vortices
can be concentrated, and if they can be concentrated, will they develop very
strongly. Whether the distributed vorticity can be centralized depends on
the angle between the direction of convective velocity and vorticity. If the
direction of convective velocity is almost parallel to the vector direction of
vorticity, it is possible for the vorticity flow to be combined by winding. If
the velocity in the axis region is very high, the vorticity will become more and
more concentrated, and eventually, the area of the vortex tube will become
smaller. So did the cyclone. Tornadoes usually stand on top of the sky. Why?
This is because in the horizontal convective wind shear zone (which can be
either in the air or near the ground), there will be a region with small vorticity