A numerical study of turbulence under temporally evolving axisymmetric contraction and subsequent relaxation

摘要: Direct numerical simulations using up to $4096^{3}$ grid points on a deforming domain have been used study the response of initially isotropic turbulence period spatially uniform axisymmetric contraction (with one extensional and two equally compressive directions) subsequent relaxation. A time-dependent strain rate is formulated closely correspond downstream evolution in wind tunnel experiments Ayyalasomayajula & Warhaft ( J. Fluid Mech. , vol. 566, 2006, pp. 273–307), with smoothly varying 4 : 1 ratio. The application leads anisotropy both large scales small scales, manner where nonlinear effects not considered rapid-distortion theory play an important role. Upon termination strain, quickly return isotropy while residual level appears persist at scales. are shown reproduce many key findings from experiments, including distinctive changes form one-dimensional spectra direction that arise sufficiently high Reynolds number, during straining relaxation periods. Scale-dependent measures presented terms versions energy spectrum. To explain observed spectral shapes, various equation representing rapid pressure slow production, transfer viscous dissipation computed, showing take dominant role when wide range exists. In particular, ‘double-peak’ number found be consequence relaxing towards much faster than comparison results obtained computational domains sizes resolutions show robust.