G. Montilla - C.V. G. EDELCA, Hydraulics Department, Basic Engineering Division, Macagua, Edo. Bolívar, Venezuela
A. Marcano - C.V. G. EDELCA, Hydraulics Department, Basic Engineering Division, Macagua, Edo. Bolívar, Venezuela
C. Castro - C.V. G. EDELCA, Hydraulics Department, Basic Engineering Division, Macagua, Edo. Bolívar, Venezuela

Experimental investigations of air entrainment inside the intakes of Guri Dam Second Powerhouse operating below critical submergence reservoir level, were carried out on a non-distorted 1 : 30 scale Froudian Physical Model. Scale effects were considered taking into consideration the – state of art – experience on physical modeling practice of submerged intakes. Prototype observations were done and compared with model results to achieve similarity between the two physical systems. Visual observations and measurements were taken inside the intake and, in the reservoir approach region to asses the behavior of the flow phenomenon under study. Turbine flow operation conditions where vortex formation occur were identified and curves forfree air entrainment flow-inside the intakes, were developed below elevation 240, design critical submergence operation of the project which adds in operating safely the 630MW units.