a branch of pneumatic and hydraulic automation. Fluid-flow devices may use a gas, including air, or a liquid and other gases as the working fluid.
The operating principles of most pneumatic and hydraulic elements and devices in fluid-flow engineering are identical (seeFLUIDICS). In some cases, however, fluidics makes effective use of the specific properties of the flow of gases. For example, the principle of proportional reduction of absolute gas pressures is based on the characteristics of the supercritical and subcritical flow of gases in constrictions. The principle is applied in the design of aerodynamic barometers, sensors that measure the ratio of absolute gas pressures, and Machmeters. Hydraulic equipment used in fluid-flow engineering also makes use of specific devices. For example, the dosing of liquids is controlled by means of siphon devices. It is possible to use pneumatic and hydraulic fluid-flow elements in combination, for example, in storing continuous signals, measuring and storing the extremal values of parameters, and simulating physical processes.
In designing hydraulic fluid-flow devices, attention is given to those characteristics of liquid flow that may cause undesirable effects, for example, cavitation or obliteration leading to the cessation of flow through small slits. In some cases, the forces of the surface tension of the liquid affect the operation of the elements.
Fluid-flow elements have a high operating reliability, and intensive work is under way in the USSR and abroad on the design of various devices and systems. Fluid-flow devices have general industrial applications and are also used in specific technical fields, for example, in control systems on ships, in oceanographic research, and in control systems for petroleum-pouring units and agricultural irrigation units.
L. A. ZALMANZON