Numerical investigation of instability mechanisms in laminar and turbulent wall jets

Secondary instability in forced laminar and turbulent wall jets is investigated using two-dimensional Navier-Stokes simulations. For modeling the turbulent flow, the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach is employed in which the turbulent mean flow and the time-dependent large coherent structures are computed time-accurately while the effect of small-scale random turbulent motion is modeled using an Explicit Algebraic Stress Model (EASM). Several parameter studies are presented indicating that subharmonic resonance may be the cause for the vortex pairing observed in experiments of forced and unforced wall jets.