Intermittency in the Process of Turbulence Evolution in a Free Jet Flow

概要

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Turbulence characteristics in the process of turbulence evolution in an air-in-air jet flow areexplored in a constant velocity region (CVR), a transitional turbulence region (TTR), and apreservative turbulence region (PTR). Swift velocity variations (i.e., turbulent velocities), whichare caused by entrainment due to the viscous shear of the fluid motion, occur intermittently inthe CVR and the TTR. The probability density function (PDF) of the turbulent velocity departslargely in the TTR from a Gaussian PDF. The scaling property in the inertial stmbrange (ISR)begins to appear in the TTR, where the turbulent velocity is internaittent even in the ISR. Fullydeveloped turbulence established in the PTR exhibits a nearly Gaussian PDF, and is basicallyintermittent at viscous subrange (VSR) frequencies. The intermittency effects are inherent inthe VSR throughout the process of turbulence evolution. The scaling property is the attribute ofthe scaling transformation invariance of the Navier-Stokes equation for an incompressible fluidin the inviscid limit. The intermittency effects are attributed to the instability of flow motion.The intermittency is not directly related to the scaling property.
社団法人日本物理学会の論文
1996-10-15