Soliton/like Coherent Structure: a Key Opening the Door of Turbulence

This review summarizes recent advances in the origin of turbulence. Soliton/like coherent structure (SCS) has been identified not only as a common structure in natural transition and K-type transition, but also as a fundamental structure in C-type, H-type, and bypass-type transitions which dominates the turbulence generation. It has also been confirmed as an essential structure in turbulent boundary layers. Notably, SCS has been successively observed in pipe flows, stratified flows, mixing layers, jet flows, falling films, and wakes. These findings collectively indicate that SCS serves as a fundamental structure in shear flows, providing significant insights into the origin of shear turbulence.