Instabilities induced in a laminar jet by acoustic hot-wires

The use of hot-wires to cause controlled and local excitation of a laminar flow and generate acoustic waves is discussed. The excitation system which consists of two hot-wires located on the edge of the nozzle is described. The observations from excitation of 6 mm and 3.8 mm laminar jets are provided. A phase relation between acoustic waves generated by the hot-wires is detected; when the acoustic waves are in phase = O axisymmetric structures are observed and when the acoustic waves are in phase = pi nonaxisymmetric structures are present.