An investigation of hydraulic transients in combination free surface and pressurized flows
Abstract
A mathematical model capable of simulating simultaneous occurrence of free surface and pressurized flows, which is termed mixed flow, is developed. This model is based on the onedimensional unsteady open channel flow equations known as the Saint Venant equations, and onedimensional unsteady equations of pressurized flow. These equations are solved by the method of characteristics on a fixed grid. Regions of pressurized flow are separarted from regions of free surface flow by a moving interfacial boundary condition. The flow at an interface advancing toward the free surface flow can be treated from energy considerations as a moving shock, the flow changing from supercritical to subcritical as it passes through the interface. Thus three characteristic equations are available for the solution at this interface plus conservation of mass and momentum across the shock plus a kinematic equation. The flow at an interface retreating toward the pressurized flow region also must be treated as a discontinuity. The mathematical model is shown to be capable of simulating the transition of an advancing interface into a retreating interface and open channel surge by comparison with experimental results.
 Publication:

Ph.D. Thesis
 Pub Date:
 1984
 Bibcode:
 1984PhDT........47C
 Keywords:

 Computerized Simulation;
 Flow Equations;
 Fluid Boundaries;
 Free Flow;
 Multiphase Flow;
 Pressure;
 Surges;
 Computer Programs;
 Fluid Dynamics;
 Mathematical Models;
 Fluid Mechanics and Heat Transfer