Coherent Structures in Turbulent Boundary Layer with Adverse Pressure Gradients

By using the idea of resonant triad of the theory of hydrodynamic stability, the coherent structures in a turbulent boundary layer were investigated as a function of steady-adverse-pressure-gradient(SAPG) and changing-adverse-pressure-gradient(CAPG) flow cases. It was found that the adverse pressure gradient enhanced the growth rate of the resonant triads, enlarged the parameter range for the growing cases, and reduced the streamwise dimension, while the spanwise spacing of the streaky structures in all four cases remained approximately the same. And the greater the adverse pressure gradient, the stronger the above effects. For CAPG flows, the case with reducing pressure gradient produced the strongest effect on the coherent structures, though the same pressure gradient was remained in the end of evolution.