A fluidic flow control device comprising at least two generally aligned members having tapering bores therethrough, the members being so arranged as to constitute a convergence followed by a gradual divergence, separated by a gap, the gap communicating with an inlet/outlet or feed port. A cage connects the adjacent ends of the members and forms said port. A system for pumping may incorporate the device between a cylinder charged with pressure gas and an out-feed pipe. In operation, fluid is alternatively drawn in through the gap and into the cylinder and then pumped out by the gas across the gap and into and through the out-feed pipe. A level detector in the cylinder controls the oscillation of the system and an accumulator may be provided to smooth the outflow. Substantially continuous flow may be provided by coupling two systems to a common out-feed pipe. A pumped flow circuit useful for heat transfer utilizes two alternately operating devices out-feeding to a single diffuser section with connected feedback passages resupplying the devices in turn.