Abstract: The sources and sinks are used to simulate the mechanical drives and the drives of the feed and withdrawals in the simulation of the flow field of a gas centrifuge for isotope separation. The new sources and sinks terms in the hydrodynamic equations are re-derived, which are different from those used in the literature. The new terms reflect the association of a type of sources and sinks with another type of sources and sinks, and the interaction of sources and sinks with the flow field, which is referred to as the coupling of the sources and sinks. Due to the coupling, which is not taken into account before, some sources and sinks terms become unknowns, which have to be determined along with the solution of the flow field. Comparing the results with and without the consideration of the coupling, it is shown that the basic flow patterns in the separation chamber are similar, but the values of the flow quantities are different and so the separative power has a quite big difference. So the sources and sinks coupling should be taken into account in the simulation of the flow field of gas centrifuges.