Visualization of a Small Jet Synthetic Using a Particle Image Velocimetry and Background-Oriented Schlieren Techniques

Abstract

This work reports the results of experimental investigations carried out on a submerged synthetic jet obtained through the use of a headset speaker piloted with an appropriate sinusoidal signal at a frequency of 380 Hz. The study begins with the construction of a device that, exploiting the well-known transport properties of impacting jets, was able to improve local ventilation and the removal of excess moisture, due to the natural transpiration of human skin in people forced to assume the same position for prolonged periods such as professional drivers; bedridden patients; etc… Subjects are substantially forced to have parts of their own body in contact with fabrics and coverings that hinder the normal conditions of skin transpiration. The experimental activity was first based on the study of the structure of the synthetic jets, then moving on to the creation of a sponge mat equipped with 80 individual jets. On this sponge mat, semi-empirical tests were carried out in order to remove moisture from a fabric soaked in distilled water. The experimental investigations were first carried out using the PIV technique, and, subsequently, the synthetic jet was visualized using the Background-Oriented Schlieren (BOS) technique which allowed to test the presence of the jets, installed directly on the mattress, in a relatively simple and fast way, requiring a very simplified set-up.