Effect of a wedge on coannular jet noise

Directional noise attenuation for a coannular jet, caused by a wedge in the fan stream, is studied with data from three different facilities. The effect, first observed with small -scale convergent nozzles at UCI , involves noise attenuation on the side away from the wedge. The trend is confirmed with data from a lar ge facility. However, several anomalies are noted. In particular, the wedge is found to be ineffective with nozzles having parallel flow lines near the exit. In the latter case, the wedge simply causes a lateral spreading of the flow. In the convergent cas e, the wedge also diverts the flow downward forming the thicker annular layer underneath that is key to the noise attenuation seen on the ground.