Effects of spanwise confinement on stratified shear instabilities

We study the influence of transverse confinement on the linear instability properties of velocity and density distributions evoking exchange flows in stratified inclined ducts. In the chosen parameter space, we find that the presence of lateral walls has a stabilizing effect. The growth-rate predictions for the spanwise-invariant cases are almost systematically an upper bound to the growth-rate corresponding to the confined geometry. In addition, accounting for spanwise-varying perturbations result in the proliferation of unstable modes that present an odd-even regularity in their spatial structures, which is rationalized by comparison to the dispersion relation obtained for oblique waves.