Unsteady pressure measurement in the presence of a cavity between the sensor and the flow

This study focuses on the measurement of unsteady pressure in gas flows with various particle admixtures using miniature piezoresistive sensors. A variant of the classical combined Pitot-Prandtl-type probe for total and static pressure measurement is considered. The pressure sensor installed in the probe is shifted with respect to the axis of the orifice, which considerably increases the sensor's lifetime. A cavity is formed between the sensor and the hole, which is a Helmholtz resonator. A new method for unsteady pressure measurement was developed for the probe under consideration. The method is based on the well-known physical model of the Helmholtz resonator, and the mathematical model in the form of a linear dynamic system with damping. The novelty of the proposed method lies in the ability to determine an arbitrary unsteady pressure in the flow over a wide range of fre-quencies, including the natural frequency of gas oscillations in the resonator neck, based on the readings of the sensor located in the cavity. The damping coefficients and resonant frequencies of gas oscillations in the holes of total and static pressure probes were determined from free damping oscillations and steady-state harmonic os-cillations. The proposed pressure measurement method was verified using the results of experiments involving the exposure of a probe to impulse pressure, conducted using the T-128 TsAGI transonic wind tunnel.