The bubble column is 2 m high and its diameter is 4 cm. Since the Lagrangian model considers the bubbles as points, the mesh does not have to be very precise (i.e. the cells do not have to be as big as a bubble). So we decided to take a mesh of 10*100. The dimensions of the column do not enable us to present the whole mesh, that is why only a part of it will be presented as it is shown in the following contours.