CFD-simulation and installation effects for ultrasonic flow meters in pipes with bends

Multipath ultrasonic transit time flow meters (USM) represent an alternative to conventional meters for fiscal gas flow measurement. When the meter is installed close to bend(s), the flow profile can be quite complex, with asymmetric axial and transversal flow profiles. To investigate the accuracy of the measurement in such situations, computational fluid dynamic (CFD) simulations of 3D flow in various bend configurations have been carried out with the finite volume CFD-code MUSIC-2.0. Simulations are compared with measurements in straight pipes of fully developed and rotating flows over a range of Reynolds numbers as well as data for one- and two-bend pipes. The question of grid independence is addressed, as well as the accuracy of the turbulence model. Calculated flow profiles are used as input to the USM uncertainty model GARUSO. The robustness of the USM towards the Reynolds number, bend types, inlet flow profiles, meter orientation and installation length from the last bend is investigated.