Explict-scales projections of the partitioned non-linear term in direct numerical simulation of the Navier-Stokes equation

TL;DR

This paper investigates the properties of partitioned nonlinear terms in direct numerical simulations of Navier-Stokes equations, focusing on filter effects and eddy-viscosity models for subgrid scale turbulence.

Contribution

It introduces explicit-scale projections of the nonlinear term with sharp cutoff filters and evaluates their independence and modeling potential in turbulence simulations.

Findings

Partitioned nonlinear terms show some independence from cutoff position.

Phase modeling of subgrid terms is poor, but amplitude modeling shows promise.

The study provides insights into subgrid scale modeling in turbulence.

Abstract

In this paper we consider the properties of the internal partitions of the nonlinear term, obtained when a filter with a sharp cutoff is introduced in wavenumber space. We see what appears to be some degree of independence of the choice of the position of the cutoff wavenumber for both instantaneous and time-integrated partitioned nonlinearities. We also investigate the basic idea of an eddy-viscosity model for subgrid terms and have found that while phase modelling will be very poor, amplitude modelling can be far more successful.