Abstract: Device, in particular for regulating and reducing the fluctuations in the composition of a polyphasic flow including at least one liquid phase and one gaseous phase. This device comprises a container for separating said phases and at least one admission opening for the polyphasic mixture, as well as means for extracting the content of the container. The extraction means (3, 7, 40, 41) extend into said container (2, 39, 56) in such a manner that during normal operation, they extend through the liquid-gas interface (6). Said extraction means include extraction openings (4, 16, 19, 50, 51) arranged on both sides of the interface in normal operation; the sum of the throughflow sections of said openings, estimated from a reference position on at least a portion of a vertical axis, varies as a function of the slope, considered on said axis and for said portion, said portion extending during normal operation on both sides of said interface.