The hydraulic mechanism ( hydro derived from the ancient Greek ὕδωρ hydor , dt. Water ) is a branch of the fluid mechanics and fluid mechanics and the continuum mechanics . It deals with the mechanical behavior of fluids (liquids and gases). Hydromechanics is divided into hydrostatics, the study of fluids at rest, and hydrodynamics , the study of fluids in motion, i.e. H. flowing fluids. If the compressibility (change in density) of the fluid is not negligible, this is no longer part of hydrodynamics, but falls within the range of gas dynamics .
An example of a hydrostatic problem is the calculation of the pressure curve in a container filled with water. If you then open a drain on this container, it becomes a hydrodynamic problem.
In technology and mechanics , one speaks of hydromechanical devices when power is transmitted or converted using liquids. The torque converter of an automatic transmission in a motor vehicle , for example, usually uses hydromechanical technology, in that the speed between the input and output shaft is matched by flowing oil.