Relationships between local topology of vortical flow and pressure minimum feature derived from flow kinematics in isotropic homogeneous turbulence

抄録

Relationships between local flow topology (geometry) of vortical flow and pressure minimum feature derived from its flow kinematics are investigated in isotropic homogeneous turbulence, in a new topological point of view with respect to vortical flow symmetry in a swirl plane. Consistency of the pressure minimum plane and the swirl plane, and relationships between the pressure minimum and vortical flow symmetry in their development are also analyzed. The pressure minimum feature is specified by the λ₂ definition and also the λˇ₂ definition that is the integrated definition of the Δ, Q and λ₂ definitions and specifies the pressure minimum in the swirl plane. The swirlity φ that represents the geometrical average of the intensity of swirling flow is applied to the statistical analysis of the flow topology and pressure minimum. It shows that the pressure minimum requires a certain flow symmetry, and that the development or decay of the pressure minimum is associated with that of the vortical flow symmetry especially in the state (process) of a vortex attaining or losing the pressure minimum feature. The vortices with high intensity of φ have the feature that the effect of vorticity components parallel to the swirl plane decreases in specifying the pressure minimum plane by the λ₂ definition, and then this pressure minimum plane tends to approach the swirl plane.