Comparative study of turbulent round jet flows through direct numerical simulation at medium–high Reynolds numbers

This study examines a spatially evolving turbulent round jet at a Reynolds number of Re = 7000 based on the bulk velocity Ub and the orifice diameter D and a Prandtl number of Pr = 0.71 using direct numerical simulation (DNS). Statistical data are collected over 30 000D/Ub time units, including mean quantities, Reynolds stresses, heat fluxes, mixed moments, Reynolds stress and turbulent kinetic energy budgets, and probability density functions. Comparative analysis with a previous DNS at Re = 3500 (Nguyen and Oberlack, 2024a; 2024c) shows that the higher Reynolds number leads to a shift of the self-similarity to a greater distance from the orifice. A larger Reynolds number leads to higher magnitudes of different statistical moments, dissipation and production. In addition, a maximum visible in the near-field of the turbulence intensity components is smoothed at the larger Reynolds number. The probability density functions of the axial velocity and the passive scalar show Gaussian behavior on the centerline, but with larger standard deviations compared to the lower Reynolds number. The study highlights the significant impact of using a fully developed turbulent pipe flow profile as the inlet condition, which significantly reduces the size of the potential core by introducing initial turbulence intensities at the orifice.