Mean flow and turbulence anisotropy representation in a round jet impingement: Experiment, DNS and modeling

The present study examines a round jet exiting a circular tube at a diameter-based Reynolds number of Reb=10000, impinging perpendicularly on a smooth wall. In addition to Particle Image Velocimetry (PIV) measurements and Direct Numerical Simulation (DNS) based on the spectral element method, a sensitized eddy-resolving RANS (Reynolds-Averaged Navier Stokes) approach with a differential Reynolds stress model (RSM) mimicking a subscale model was applied to generate a flow database comparable across multiple methods. Within the framework of the scale-resolving RANS–RSM, the turbulent correlations governing the dynamics of the entire subscale stress tensor are obtained as solutions to an appropriately extended set of RANS-based model equations that describe the evolution of the corresponding turbulence quantities. The representative subscale turbulent length and time scales that constitute the relationships entering the relevant equations of motion are determined by using the unresolved residual part of the turbulence kinetic energy and its viscous dissipation rate. The detailed mean flow and associated turbulence correlations, evaluated together with some global characteristics (e.g., wall shear stress), enabled a deeper insight into the topological flow properties and facilitated a critical assessment of the modeling approach through direct comparison with the complementary experiment and direct numerical simulation. Additionally, the study contributes to turbulence anisotropy characterization based on three-dimensional mapping of Reynolds stress anisotropy properties using Lumley's classical representation of anisotropy invariants as well as barycentric coloring. The two-component invariant parameter field exhibits fairly high, close-to-unity values, indicating a weak level of anisotropy consistent with the conditions that characterize the destabilizing effect of strong local streamwise curvature in flows subjected to stagnation. The turbulence structure is constrained within the range between the three-component and two-component isotropic bounds, which underlies the axisymmetric contraction state of turbulence, consistent with the negative values of the third invariant of Reynolds stress anisotropy.