Analysis of upstream installation effects on the discharge coefficients of averaging Pitot tubes using CFD

It is difficult to acquire or calibrate the discharge coefficient of averaging Pitot tubes, especially for large diameter pipes. Simulations and experiments were carried out to obtain the measurement characteristics at the situation where there are not enough long straight pipe to ensure the fully developed fluid. The goal of this paper is to do some preliminary numerical tests on acquiring or calibrating the discharge coefficient of averaging Pitot tubes applied at the large diameter pipes with upstream single elbow, double elbows in-plane or double elbows out-of-plane. Standard k-ε turbulence model was used in simulations. The velocity profile of downstream elbows was illustrated and investigated. The discharge coefficients of averaging Pitot tubes are obtained from both simulation and experiments. The results show that the disturbed flow results in positive or negative shifts for the discharge coefficients. In terms of deviations of the coefficient downstream elbows and that at fully developed flows, and with prediction models, some attempt can be made to correct the coefficient with elbows upstream in large-diameter conduits.