Lattice Boltzmann equation simulation of rectangular jet (AR=1.5) instability and axis-switching

We investigate the axis-switching and instability onset characteristics of a rectangular jet with aspect ratio (AR) of 1.5. Jet flow simulations of four different Reynolds numbers, 10,100,150, and 200, are performed. Half-width of streamwise velocity along with velocity vector and streamwise vorticity on transverse planes at different downstream locations are examined. The simulation results show the following instability characteristics: (i) At relatively low Reynolds numbers (10 and 100), the jet flow is laminar and stable; (ii) At Re=150, the flow is still laminar and stable but axis-switching occurs with downstream distance; and (iii) At Re=200, the jet flow becomes unstable but the axis-switching is still seen roughly. Instability first originates near the jet orifice and then propagates down the stream.