To model this test apparatus with the SOLA-VOF code, it is necessary to supplement the code with calculations for the gas pressure in the pipe and for the pressure in the space above the pool surface. These pressures are then used as free surface boundary pressures. A sequence of calculated results illustrating the fluid dynamics associated with the air clearing process are contained in Fig. 13. The free boundaries obviously undergo severe distortion, but the SOLA-VOF algorithm has no