Shock Structure and Ultrasound Emission in a Supersonic Jet

We study the shock structure and the ultrasound emission in a supersonic jet using Rayleigh Scattering in two different ways. On one side we visualize the shock waves and on the other we obtain the frecuency spectrum of density fluctuations for a wave-vector determined by the optics. In an axisymmetric jet we have found that besides the ultrasound fluctuations that travel at the speed of sound there are others that travel at slow velocity and are apparent very close to the shocks. We are trying to understand the origin of these slow fluctuations and determine their relationship with shocks and if they appear in other geometries. We also present the ultrasound emission pattern inside and outside the jet.