Numerical Solution of 2-Dimensional Flows through Butterfly Valve Using Overset Grid Technique.

The overset grid technique is applied to simulation of 2-dimensional flows through a butterfly valve. The numerical simulation for valve openings of varying numbers of degrees can be carried out using the same grid system of a minor grid around the disk and a major grid in the channel. The rational Runge-Kutta scheme with implicit residual averaging and local time stepping techniques is employed as the time integration method. This time integration method is effective for obtaining a high convergence ratio to a constant solution, though it is an explicit scheme. The results are obtained for valve openings of 45°and 60°. The figures of the velocity vector show two vortices behind the disk. These typical flow patterns are in agreement with those of experiments. The loss coefficient obtained for each valve opening also agrees with those of experimental data.