Open AccessIn running hydro-mechanical systems there are situations, which can lead to the rupture of fluid, i.e. fluid vapor appearing due to a drop in pressure (cavitation). In case it is not taken into account in simulation, there may occur a negative pressure as a result of calculation, which is clearly untrue. The article offers an option to take the fluid rupture into consideration in modeling hydro-mechanical systems with lumped parameters, that is the case when a mathematical model of the hydro-mechanical system is a system of nonlinear ordinary differential equations. At this level of modeling the mere fact of taking into consideration the fluid rupture and the time of its existence, rather than the process of vapor bubbles generation and collapse, is important. According to the proposal, the emerging rupture of fluid may be taken into consideration owing to essentially weightless 10-8 kg membrane, being at the fluid-vapor interface and under the fluid pressure, on the one hand, and under the saturation vapor pressure, on the other one.
The fluid and vapor parameters in this case are not mixed and may depend on various factors, e.g. temperature, pressure. Dependencies can be both analytical and tabular. The model is represented in the form of an equivalent schematic diagram, and a system of equations. The article presents the calculation results of the test scheme performed using the complex ПА9 and the proposed model. The fluid ruptures in hydraulic cylinder to the rod of which the force is applied. These results are supported by simple hand calculations, thereby proving the adequacy of the developed model of the fluid rupture. The model is suitable for any software system to analyse the systems with lumped parameters. At the model level publications concerning the fluid rupture (cavitation) exists in the form of differential equations in the partial derivatives, but they are essentially unavailable at the model level in the form of ordinary differential equations. The AmeSim package contains a model of fluid, which disables negative pressures, but implementing a dependency of the modulus of fluid elasticity on the pressure allows us to achieve it.