Figure 1. (a) Butterfly valve disk tetrahedron mesh, (b) the flow domain extended 2D and 6D upstream and downstream the valve respectively for disk angle (α=70°)

From

The Accuracy Degree of CFD Turbulence Models for Butterfly Valve Flow Coefficient Prediction

Mohammed M. Said, Hossam S.S. AbdelMeguid, Lotfy H. Rabie

American Journal of Industrial Engineering. 2016, 4(1), 14-20 doi:10.12691/ajie-4-1-3