Experimental Investigation of a Line-Cavity System Equipped with Fiber-Optic Differential Pressure Sensors in a Shock Tube

The aerodynamic behavior inside a line-cavity system is investigated within this work. Acoustic effects, like attenuation and resonance, are mainly dependent on the geometric line-cavity system properties: radius r, line length L and cavity volume V. In order to determine the transfer function from the system entry to the location of the pressure sensor at the cavity end, newly developed fiber-optic differential pressure sensors are used to acquire signals of high bandwidth. In contrast to approaches in the frequency domain, where e.g. a speaker emits signals of dedicated frequencies, in this work, the transfer function is calculated in the time domain. A step pressure change in a shock tube is produced and leads to the excitation of frequencies in a large bandwidth simultaneously. In addition to the fiber-optic pressure sensor at the end of the line-cavity system, a further fiber-optic sensor is flush mounted to the shock tube test section as a reference. By applying system-identification routines, the transfer function can be deduced. Experimental investigations of two line-cavity systems of various lengths show very good results. The signals of the reference pressure signals can be reproduced very accurately.