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 dampin g on the measured pressure fluctuations was proposed. A mathematical m odel of the measuring system was formed combining the governing equati ons of the unsteady flow in the rigid connection tubing and the corres ponding volumetric deformation in the transducer. Numerical solution o f 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 si nusoidal pressure variations. Amplification and attenuation of sinusoi dal pressure variations were given in terms of dimensionless parameter s. An in situ dynamic calibration to obtain lumped compliance of the m easuring system was described. The method was applied to correct the m easured pressure fluctuations obtained from different sources. The mat hematical and numerical model was successful in correcting amplificati on and attenuation occurring on different frequency bands of the same pressure record with random fluctuations.