DNS Study on Hairpin Vortex Structure in Turbulence

A forest of hairpin vortices has been accepted widely as the common vortex structure in turbulent flow. It is commonly believed that the hairpin has leg, neck and ring head and the leg is attached on the wall. In our DNS study, it is found that the leg and ring head are separated and generated by different mechanisms. In addition, the ring head is Omega-shaped and separated from the leg and the leg is detached from the wall from beginning. The leg is not a vortex tube in any sense. I