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Evaluation of fluctuating pressures measured with connection tubes

The dynamic characteristics of fluctuating pressure measuring systems composed of connection tubing and pressure transducers were analyzed. A method of correction for the effects of resonance and viscous damping on the measured pressure fluctuations was proposed. A mathematical model of the measuring system was formed combining the governing equations of the unsteady flow in the rigid connection tubing and the corresponding volumetric deformation in the transducer. Numerical solution of the governing equations were described. The phase shift between the velocity amplitude on the tube axis and the maximum wall shear stress was obtained from numerical solutions for a wide frequency range of sinusoidal pressure variations. Amplification and attenuation of sinusoidal pressure variations were given in terms of dimensionless parameters. An in situ dynamic calibration to obtain lumped compliance of the measuring system was described. The method was applied to correct the measured pressure fluctuations obtained from different sources. The mathematical and numerical model was successful in correcting amplification and attenuation occurring on different frequency bands of the same pressure record with random fluctuations.