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Title: Computation Of Flow In An Orifice Meter Installation
Author: m. Z. Sheikholeslami, K. Kothari, B. R. Patel
Source: 1990 International Symposium on Fluid Flow Measurement
Year Published: 1990
Abstract: Computations are carried out to determine the performance of an orifice meter in typical field installations consisting of two in-plane and out-of-plane 90 degree elbows upstream of the orifice plate. The numerical results show that if there is a sufficient length between the elbows, the exit velocity profile of two in-plane and out-of-plane elbows are similar. At the exit from the second elbow there exist two counter-rotating secondary flow vortices superimposed on the axial flow. The axial velocity profile is severely distorted. The non-uniformity in velocity profile is defined as (Umax - Umin)/Uave x 100 where u/*, #mw* and Uave are the maximum, minimum and average axial velocities, respectively. Based on this definition the axial velocity non-uniformity at the exit of the bend is about 20%. Computation of flow field through an orifice meter model, using the exit velocity profile in the in-plane bend sub-model as an inlet velocity profile, indicated that the maximum error in the discharge coefficient is less than two percent. This was due to the long straight section that was used between the bend sub-model and the orifice sub-model. This long section allows the axial velocity distortion to decay before reaching the orifice plate. The numerical results were in agreement with the available experimental data.