Spiral ( swirling ) flow is a sort of special and regular vortex movement. Spiral flow is widely used in industry, e.g. in jet technology, combustion technology, pneumatic transportation, cyclone separators. Researchers have done a lot of investigations about spiral flow. Moreover, spiral flow can be seen frequently in nature, such as tornado. Once we master the rules of spiral flow, we can develop better capability and better efficiency spiral flow generators. This has evident engineering value...