Investigation of chevron synthetic jets flow field and heat transfer

The present thesis analyses the effect of a saw-tooth exit pattern, called chevron exit, on the flow field and heat transfer of a synthetic jet. The chevron exits are generally applied at the trailing edge of jet engine nozzles for acoustic noise reduction and mixing enhancement. For the present study, the synthetic jet is obtained by a loudspeaker as oscillating element and a contoured nozzle as inlet/outlet aperture. Two experimental techniques are used: Stereoscopic Particle Image Velocimetry for the two-dimensional three-component flow field measurements and Infrared thermography in conjunction with the heated thin foil heat transfer sensor for the heat transfer measurements. Owing to the peculiar features of synthetic jets and the effect of the chevron elements on the coherent structures organisation, the chevron exit could lead to a heat transfer enhancement. It is shown that this kind of nozzle can produce an increase of turbulence intensity levels in some regions of the field and entrainment and mixing enhancement by introducing streamwise coherent structures.