ul. T. Baramzinoi, 34, Izhevsk, 426067, Russia
Institute of Mechanics Ural Branch of the Russian Academy of Sciences
Raeder T., Tenenev V. A., Chernova A. A.
Incorporation of Fluid Compressibility into the Calculation of the Stationary Mode of Operation of a Hydraulic Device at High Fluid Pressures
2021, Vol. 17, no. 2, pp. 195-209
This paper is concerned with assessing the correctness of applying various mathematical models for the calculation of the hydroshock phenomena in technical devices for modes close to critical parameters of the fluid. We study the applicability limits of the equation of state for an incompressible fluid (the assumption of constancy of the medium density) to the simulation of processes of the safety valve operation for high values of pressures in the valve. We present a scheme for adapting the numerical method of S. K. Godunov for calculation of flows of incompressible fluids. A generalization of the method for the Mie – Grüneisen equation of state is made using an algorithm of local approximation. A detailed validation and verification of the developed numerical method is provided, and relevant schemes and algorithms are given. Modeling of the hydroshock phenomenon under the valve actuation within the incompressible fluid model is carried out by the openFoam software. The comparison of the results for the weakly compressible and incompressible fluid models allows an estimation of the applicability ranges for the proposed schemes and algorithms. It is shown that the problem of the hydroshock phenomenon is correctly solved using the model of an incompressible fluid for the modes characterized by pressure ratios of no more than 1000 at the boundary of media discontinuity. For all pressure ratios exceeding 1000, it is necessary to apply the proposed weakly compressible fluid approach along with the Mie – Grüneisen equation of state.
Chernova A. A.
Limitation of the contact angle in the problem of a drop of a liquid on a vibrating substrate
2017, Vol. 13, No. 2, pp. 165-179
The article deals with the process of fluctuations of a liquid droplet of a small volume lying on a vibrating hydrophobic rigid substrate. The study is carried out by the numerical simulation method of Euler fluid volume (Volume of Fluid — VoF). We study problems of accounting for dynamic changes in the contact angle at the triple point of the liquid-substrate-to-air as well as the impact of changes in the range of the contact angle on the processes that accompany the forced oscillations of the drop. Particular attention is paid to topological features formed in a drop of internal flows. The connection between the interaction of different surface effects, transformation of internal flows, the size limit changes in the contact angle of the substrate and the phase fluctuations are considered in detail. All numerical results are compared with experimental data.