Assessing the Effects of Local Turbulence and Velocity Profiles on Electromagnetic Flow Meter Accuracy

The purpose of this research was to assess the effects of local turbulence and velocity profiles on electromagnetic (magnetic) flow meters. According to the American Water Works Association, “No tool available to water utilities has played a greater part in the conservation of water than the water meter (AWWA 2002).” Consequently, it is imperative to understand what variables may influence magnetic flow meter accuracy. Even though other researchers have explored the effects of turbulence profile development on orifice plates, the literature is not clear how magnetic flow meters respond to the effect of local turbulence. Accordingly, this study investigated the effects of local turbulence and velocity profiles on magnetic flow meter accuracy. Using five magnetic flow meters from five different manufacturers, laboratory tests were conducted with a CPA 65E flow conditioner located at different distances upstream of the meter. Numerical modeling using commercially available computational fluid dynamics software indicated that the deviations in flow meter accuracy were not proportional to the levels of local turbulence. It appears that magnetic flow meters may only be influenced by local turbulence to the degree that the upstream disturbance that distorts the velocity profile also increases local turbulence