Non-Linear Instabilities of Two Supersonic Wall Bounded Jets Impinging at an Angle

The impingement of two planar, wall-bounded jets angled towards each other leads to several non-linear instabilities.

These instabilities depend upon the ratio of the jet height to jet separation distance. 

We present a computational study that identifies the primary non-linear instabilities in this flow using a discontinuous Galerkin based Navier-Stokes solver. 

Two-dimensional and three-dimensional simulations are conducted.

Three cases of varying jet heights are considered.

For the smaller jet heights the impingement leads to a non-linear instability and oscillatory, shocked, vortex dominated flow that mixes the two jets.

For the larger jet height the the supersonic jets merge along the centerline and a non-linear shear instability develops.

This instability induces an oscillatory motion both jets while they remain aligned.

The oscillation frequency is lower in the larger jet height case than the smaller jet height cases.

The onset of three dimensional structures and is traced back to the recirculation region. 

An upstream propagating wave impacting the wall causes instabilities along the span of the planer jets.