Influence of the spatial resolution on fine-scale features in DNS of turbulence generated by a single square grid

TL;DR

This study examines how the spatial resolution of DNS affects the detailed turbulence features downstream of a square grid, validating the approach with experiments and analyzing flow dynamics through Q-R diagrams.

Contribution

It provides a validation of DNS against experimental data and investigates the impact of resolution on turbulence dynamics using Q-R diagrams.

Findings

Good agreement between DNS and experiments for one-point statistics.

Resolution influences the ability of DNS to capture turbulence features.

Under-resolved DNS can still reproduce main turbulence characteristics.

Abstract

We focus in this paper on the effect of the resolution of Direct Numerical Simulations (DNS) on the spatio-temporal development of the turbulence downstream of a single square grid. The aims of this study are to validate our numerical approach by comparing experimental and numerical one-point statistics downstream of a single square grid and then investigate how the resolution is impacting the dynamics of the flow. In particular, using the Q-R diagram, we focus on the interaction between the strain-rate and rotation tensors, the symmetric and skew-symmetric parts of the velocity gradient tensor respectively. We first show good agreement between our simulations and hot-wire experiment for one-point statistics on the centreline of the single square grid. Then, by analysing the shape of the Q-R diagram for various streamwise locations, we evaluate the ability of under-resolved DNS to capture the main features of the turbulence downstream of the single square grid.