A comparative turbulent flow study of unconfined orthogonal and oblique slot impinging jet using large-eddy simulation

Abstract

The incompressible turbulent flow field of the slot impinging jet has been studied numerically at a Reynolds number of 7900 and d = 6w using large-eddy simulation with the wall adapting local eddy-viscosity subgrid-scale model for the angles of impingement 70° and 90°. The validity of the computation is confirmed by reasonable comparisons of the wall shear stress, pressure variation over the impingement plate, jet-centerline velocity, and second-order turbulent properties with past experimental and numerical results. The turbulent stress, turbulent length scales, and turbulent structure sizes are observed to be increased in the oblique impingement. The appearance of the oblate spheroid-shaped, three-dimensional isotropic, and prolate spheroid-shaped turbulence has been marked in the wall-jet region using the anisotropy invariant map. The power spectra of the fluctuating field maintain the −5/3 slope in the inertial subrange, which as expected becomes steeper in the dissipation range, as stated by Kolmogorov. Both positively skewed and negatively skewed fluctuations are seen in the flow field, and their probability density functions suggest that the fluctuation range increases in the case of oblique impingement. The involvement of various shearing and swirling structures has been investigated employing the proper orthogonal decomposition, the Q- function, and the λ2- function, where the isosurface of vorticity components is used to represent the direction of rotations.