What Is Liutex?

A vortex is a common phenomenon that occurs in fluid flow, especially when studying turbulence. It is to say, understanding vortices is essential knowledge for scientists, researchers, and engineers doing work in the field of fluid mechanics. In the past, scientists such as Helmholtz had a desire to understand the physical nature of vortices and popularized the idea of using vorticity to define a vortex in a fluid field. Vorticity became the default for studying vortices and new vortex identification methods were created that were built-on the idea of vorticity. This went on for a long time until only recently, Dr. Chaoqun Liu discovered the Liutex method. The Liutex method started a new generation of vortex identification methods. Liutex is based directly on the rotation of a fluid as opposed to vorticity which also contains shear. It has been shown that vorticity cannot distinguish between shear and rotation. A counterexample for the invalidity of vorticity to define a vortex can be found in the laminar sub-layer near the boundary wall of the boundary layer where vorticity is large but there is no rotation. Liutex has now become a well-known vortex identification method. Researchers around the world agree that Liutex mathematically defines what a vortex is. In this presentation I hope to explain what Liutex is.