The joint motion of gas and liquid forming a gas-liquid system is considered. The forms of joint motion of gas and liquid are investigated as the motion of two continuous ones interacting along the interface of flows before the movement of the foam flow, in which both phases form a complex, thin and unstable structure. Forces arise on the interfaces, which, even in an isothermal flow, have a significant effect on the fields of flow characteristics. Simulation of the similarity of gas-liquid flows in theoretical terms is presented. Complexes and linear scales of gravitational-viscous interaction of falling films of a viscous liquid caused by molecular viscosity have been obtained.