Calculation of scalar structure functions from a vortex model of turbulent passive scalar transport

Abstract

A Saffman and Pullin [Phys. Fluids 8, 3072 (1996)] type vortex model for passive scalar structure functions is formulated. The intermittent turbulent fine-scale dynamics in the model is represented by numerical solutions of the advection-diffusion and Navier-Stokes equations in the form of axially strained vortex-scalar structures. The use of these structures is motivated by Pullin and Lundgren's [Phys. Fluids 13, 2553 (2001)] asymptotic strained spiral vortex model of turbulent passive scalar transport. Ensemble-averaged scalar structure functions, of even orders 2-10, are calculated from a range of vortex-scalar structures using Monte Carlo integration. For axisymmetric strained scalar fie..