Detailed Flow Field Structure in Rapid Valve Closure

In this paper the detailed structure of velocity and pressure fields during and subsequent to instantaneous valve closure are presented. The full Navier-Stokes partial differential equations, formulated for a two-dimensional axi-symmetric flow geometry, have been solved to obtain the transient solutions. The Finite Volume Integration Technique together with a procedure involving splitting of operators is employed instead of the Method of Characteristics which is commonly used in the numerical solution of transient flows in pipelines. A solution in two dimensions, viz., in both the pipe axial and radial axis, is obtained for velocity and pressure. The well known oscillations of both the pressure and velocity components have been confirmed. However, it has been revealed, in this work, that the velocity field has a lot of structure in the radial axis which includes a region of re-circulation flow immediately upstream of the closed valve.