Ivan Vozhakov

Peculiarities of evolution of shock waves generated by boiling coolant

Simulation of compression wave generation and evolution at the disk target was performed for the case of explosive-type boiling of coolant; the boiling is initiated by endwall rupture of a high-pressure pipeline. The calculations were performed for shock wave amplitude at different times and modes of pipe rupture. The simulated pressure of a target-reflected shock wave is different from the theoretical value for ideal gas; this discrepancy between simulation and theory becomes lower at higher distances of flow from the nozzle exit. Comparative simulation study was performed for flow of two-phase coolant with account for slip flow effect and for different sizes of droplets. Simulation gave the limiting droplet size when the single-velocity homogeneous flow model is valid, i.e., the slip flow effect is insignificant.

Modeling wave processes at the outflowing of a water coolant with supercritical initial parameters

Numerical simulation of the outflow of a coolant with supercritical initial parameters at a butt-break of high-pressure pipeline is carried out. The results of calculation of the outflow dynamics on a PV-diagram, as well as the pressure evolution are presented. It is shown that the flow rate weakly depends on temperature at its low values (up to 0, 9 Tc ). In the second region (from 0, 9 Tc to Tc ), the coolant boiling occurs inside the channel, which leads to a sharp drop in the flow rate with increasing temperature. And the third area (above Tc ) is typical for the gas coolant outflow, in which the density strongly depends on pressure and temperature.

Simulating nonlinear waves on the surface of thin liquid film entrained by turbulent gas flow

A new system of equations has been derived to simulate the dynamics of long-wave perturbations on the surface of a thin layer of viscous liquid, flowing down a vertical plane and blown by co-current turbulent gas flow. The analysis of linear stability of the unperturbed flow has been performed. It has been found that at moderate Reynolds numbers of liquid, Benjamin linear model and model of boundary conditions transfer to the unperturbed level for a disturbed gas flow give qualitatively similar results. With decreasing Reynolds number differences between the results obtained by different turbulence models become more pronounced. In the case of small Reynolds numbers of fluid, the system of equations results in a single evolution equation for film thickness deviation from the undisturbed level. Some solutions of this equation have been considered.

Wave processes at outflow of water coolant with initial supercritical parameters

Simulation is presented for the case of water coolant outflow with initial supercritical parameters after high pressure pipeline breaking. The nonequilibrium relaxation model of phase transition was developed and validated. The model describes both boiling and condensation processes.

Simulating the nonlinear wave mode evolution in the problem of the falling thin layer of a viscous liquid

The work is devoted to numerical simulation of the dynamics of nonlinear periodic waves on the surface of freely flowing liquid film realized with the use of the previously discovered symmetry of model equations. The calculation results have been presented for the dynamics of amplitudes of significant harmonics and for the wave surface evolution. They prove to be in good agreement with previously calculated steady-state traveling solutions obtained on the full and the reduced bases. In addition, the work has identified intervals of wavenumbers in which the evolution of perturbations with small initial amplitude leads to a wave signal periodically changing in time rather than to the steady-state traveling solution.

Symmetry in the problem of wave modes of thin viscous liquid layer flow

Abstract The equations in conservative form for modelling nonlinear waves on a liquid film flowing down a vertical plane have been investigated. It has been found out that the equations with boundary conditions are invariant under parity transformation in the extended computational domain. The steady-state travelling solutions are numerically shown to have the detected symmetry for moderate Reynolds numbers. The use of this symmetry for the numerical solution of the problem by Galerkin methods significantly increases the efficiency of calculations.