Pressure tap cavity for unsteady aerodynamic pressure measurements

Extensive laboratory experiments were carried out to investigate the effect of a cavity behind the pressure tap on unsteady aerodynamic pressure measurements. The volume of the studied cavity (truncated cone) is 1.5 mm³ behind the pressure tap (cylinder) of 1 mm³ and the studied frequency range is up to 256 Hz. This design with a cavity behind the pressure tap and the studied frequency range are common for a wide range of mechanical, civil, aerospace, and environmental engineering applications. The experiments were performed using three different facilities, i.e. a signal generator, a low-turbulence wind tunnel, and a high-turbulence wind tunnel. Conclusions were made based on the quantitative analysis of the peak amplitude and frequency of the amplitude spectral density of pressure fluctuations as well as on the standard deviation of pressure fluctuations. Results were qualitatively analyzed with respect to phase shifts and amplitude deviations. The results clearly indicate that a 2.5 mm³ cavity with a pressure tap is suitable for unsteady pressure measurements in the frequency range up to 256 Hz as the phase shift and amplitude deviation of the unsteady pressure signal in those conditions proved to be negligible.