Congenital heart diseases affect about 130 million children worldwide, and single ventricle syndrome is one of these heart diseases. Children with this type of pathology are born with this malformation in the heart, i.e., absence of the ventricle responsible for carry out blood rich in carbon dioxide to the lungs. The correction of the malformation is performed through Fontan s surgery, which needs to be done in the first years of life. In this procedure, the venas cava are connected directly to the pulmonary arteries. Many studies search for the improvement of this technique, aiming to a higher life expectancy. The success of this surgery depends on the appropriate blood flows distribution, so that the distribution after Fontan procedure will be closer to the blood flow distribution of a healthy person. This study seeks to numerically determine the volumetric fractions of blood flows that leave each vena cava and arrive in each pulmonary artery, aiming to identify the success of the surgery, as well as provide subsidies to improve the procedure. In this work, it was used as a strategy to evaluate these results, modeling the flow using the two-phase flow formulation VOF, with both phases, having the same properties.