Transient perturbation growth of vortex rings

The Science of Making Torque from Wind

Chen, Fei^1 ; Wang, Bofu^1 ; Wacks, Daniel^1 ; Cabezon, Daniel^2 ; Mao, Xuerui^1

School of Engineering and Computer Sciences, Durham University, Durham

DH1 3LE, United Kingdom^1

EDPREU, Serrano Galvache 56, Madrid

28033, Spain^2

关键词: Azimuthal wave number;    Breakdown process;    Initial perturbation;    Optimal perturbation;    Transient energy growth;    Transient perturbation;    Vortex rings;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/753/3/032049/pdf
DOI  :  10.1088/1742-6596/753/3/032049

来源: IOP

【 摘 要 】

Perturbations to a vortex ring with largest transient energy growth are calculated and applied to drive the vortex ring to evolve. Optimal initial perturbations appear at azimuthal wave numbers β = 0 and β = 9. The former was described as 'axial flow' and is not related to the breakdown of the ring, while the latter is critical to the ring breakdown process as observed in previous direct numerical simulation (DNS) with random initial noise input. In the present work, DNS is conducted to study the nonlinear development of the optimal perturbations, and good agreement with past studies is achieved.