The results of experimental and numerical investigations of the development of two-dimensional determininistic disturbances in the case of Rayleigh–Taylor instability and transition to turbulence on the gas-liquid interface are presented. The experiments were performed on a light-gas gun. Disturbances at the interface were produced by means of gun oscillations using a special device. The disturbance wavelength varied from 5.4 to 8.8 mm, their amplitude from 0.3 to 0.4 mm, and the liquid layer acceleration from 5.2 to 18.8 mm/ms2. Water was used as a fluid and compressed air as a gas. The experimental data on the disturbance transition to the turbulent stage are obtained. The experiments are accompanied by the numerical modeling using the EGAK code. The criteria of instability transition to the turbulent stage are proposed.

This paper presents results of computational and experimental studies of the evolution of turbulent mixing in three-layer gas systems with the development of hydrodynamic instabilities, in particular, the Richtmyer–Meshkov and Kelvin–Helmholtz instabilities, under the action of shock waves. One of the contact boundaries between gases is flat, while the other one has the form of a chevron. The numerical simulations are carried out both with and without initial perturbations of contact boundaries. It is shown that the roughness of the contact boundary significantly affects the width of the mixing zone.

This paper describes the use of a phenomenological model of anisotropic turbulence for studying the development of turbulence in the gravity field on the plane interface between two incompressible fluids (gases) with density ratio of ρ2/ρ1 = 3. The case, when at some time the acceleration changes its sign, is considered. The calculated results are compared to the 3D results of the direct numerical simulation with the CFD code and the corresponding experimental data.

This paper presents the experimental and numerical results of studying the growth dynamics of the deterministic and given initial perturbations defined in a certain way. The formation, growth, and further evolution of inhomogeneities of the contact boundary occurs due to the development of the Rayleigh–Taylor instability (RTI) at the gas-liquid interface, and in particular (in this study), the air-water interface. The significant difference in the densities of the selected substances leads to a noticeable slowdown in the dynamics of the Kelvin–Helmholtz instability (KHI), which is responsible for the formation of mushroom-like structures, and, as a result, to the longer growth of water jets and the later moment of their destruction and transition to mixing. In this study, a quantitative comparison of the physical data recorded on the original experimental setup, which is described in this paper, with the calculated data obtained using various numerical methods is carried out. The numerical modeling is based on a complete 2D hydrodynamic model for describing the dynamics of the development of the RTI. The surface tension (water-air) and viscosity (water or air) are neglected in this study. The parameters of the development of the instability measured in the experiment and found in the calculations indicate satisfactory agreement between the obtained data. The quantitative results presented in this study justify the use of the classical hydrodynamics model to describe the movements of liquid and gas observed in this experiment and the fairly accurate numerical implementation of the corresponding model in the difference methods used here. The investigation of the development of turbulent mixing depending on well-defined initial conditions and the new regularities of the laws of mixing of the media of different densities that arise in this case is an important element in the study.

В настоящей работе представлены экспериментальные и численные результаты исследования динамики роста детерминированных, определенным образом заданных начальных возмущений. Возникновение, рост и дальнейшая эволюция неоднородностей контактной границы происходит благодаря развитию неустойчивости Рэлея-Тейлора на границе раздела газ-жидкость, в частности (в данной работе), воздухвода. Существенная разница плотностей выбранных веществ приводит к заметному замедлению динамики неустойчивости Кельвина-Гельмгольца, отвечающей за образование грибообразных структур, и, как следствие, к более длительному росту струй воды и более позднему моменту начала их разрушения и перехода к перемешиванию. Выполнено количественное сопоставление натурных данных, зафиксированных на оригинальной экспериментальной установке, описание которой приводится в настоящей работе, с расчетными данными, полученными с использованием различных численных методик. В основе численного моделирования лежит полная 2D гидродинамическая модель описания динамики развития неустойчивости Рэлея-Тейлора. Поверхностным натяжением (вода-воздух) и вязкостью (воды или воздуха) в данном исследовании пренебрегается. Измеренные в эксперименте и найденные в расчетах параметры развития неустойчивости свидетельствует об удовлетворительном согласии полученных данных. Приведенные в данном исследовании количественные результаты оправдывают использование модели классической гидродинамики для описания наблюдаемых в данном опыте движений жидкости и газа и достаточно точную численную реализацию соответствующей модели в применяемых здесь разностных методиках. Существенным элементом проведенного исследования является изучение развития турбулентного перемешивания в зависимости от вполне определенных начальных условий и возникающих в этом случае новых закономерностей законов перемешивания разноплотных сред.

This paper describes the formulation and calculation results obtained using the Euler gas aerodynamic code (EGAC) of interaction between a shock wave and a turbulent mixing zone, which develops on a flat interface separating air and argon. The study is carried out using both direct numerical three-dimensional modeling and a two-dimensional $$(k-\varepsilon)$$ turbulence model. A comparison is made with the results of experiments in which the expansion and stratification of a shock wave is observed during its propagation after passing through a turbulent mixing zone. Calculations are carried out using the ( $$k-\varepsilon$$ ) model and with account for the presence of a boundary layer, which make it possible to explain this effect.

Formation of a vortex ring in the process of rising a heated light volume of air medium in the Earth’s gravity field is investigated. The results of calculations carried out on various computational grids are compared both with each other and with solutions of the approximate analytical theory of formation and motion of a buoyant vortex ring approved by the available experimental data. A good agreement between all the data is obtained.

An analytical solution for the self-similar stage in the problem of gravity-induced turbulent mixing in a light (heavy) layer is obtained on the basis of the k–ε model equations. The solution obtained is compared with the results of a numerical investigation of the problem using both three-dimensional direct numerical simulation and the k–ε model. The calculations were performed using the two- and three-dimensional versions of the EGAK method. The results of all the calculations and the available experimental data are in reasonable agreement.

An investigation is made of the dynamics and visible-range luminosity of the plasma cloud produced behind the front of a shock wave in air at a pressure of 1 Torr. The shock wave was produced on introducing the radiation of the twelve-channel Iskra-5 laser facility with a total energy of ∼2300 J into a hollow spherical plastic target of mass ∼10-4 g. Experimental data are compared with simulations.

The interaction of plasma clouds generated during laser irradiation of a spherical target in a background gas with a magnetic field was studied on the MKV-4 test bench of the Iskra-5 facility. The dynamics of the plasma cloud expansion in a 300- to 500-Oe magnetic field was investigated using magnetic and probe diagnostics. The results obtained are compared with calculations by different models of laser plasma diffusion in a magnetic field.

Results are presented from studies of the spectral characteristics of a glowing plasma object that forms behind a shock wave propagating in a background gas at a pressure of 1 Torr after laser irradiation of a spherical organic target in the MKV-4 device (a component of the Iskra-5 facility). The experimental data are compared to the results of calculations.

Results are presented from experimental and theoretical studies of a glowing plasma object emerging behind a shock front that propagates through the background gas at a pressure of p 0 = 6 torr after laser irradiation of a hollow spherical target. The results of calculations are compared to the experimental results obtained in the MKV-4 device (a component of the Iskra-5 facility).

3D gas-dynamic techniques is used to study turbulence in the gravitational field at a plane interface of two incompressible fluids with density difference n=3. The case is considered, where the acceleration changes its sign at a certain time. The computed data is compared to the computations by the phenomenological kappa-epsilon model and relevant available experimental data.