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Results of 2D numerical simulations of thermonuclear burning propagation in a helium layer on a neutron star surface using the Euler-Lagrange TIGR-3T code are presented. This process is crucial for the development of type I X-ray bursts. Ignition and thermonuclear burning propagation are fairly easy to obtain when simulating a layer with a density at the bottom of 1.75 × 108 g cm−3. Such a simulation allows it to be compared with previous simulations based on other codes, including the simulation based on the MPM code described previously. However, this density is two orders of magnitude higher than can be obtained in observed bursters. The implementation of efficient numerical methods for the description of heat conduction and turbulence in the TIGR-3T code has allowed simulations to be performed for a layer with a density at the bottom of 1.8 × 107 g cm−3. The fulfilment of certain conditions on the size and shape of the initial temperature perturbation is required for the propagation of thermonuclear burning. Simulations reveal a peculiar burning propagation mechanism through compression of the layer ahead of the burning front by the matter transferred above the free surface.

Two-dimensional calculations by the TIGR code [Izv. Sib. Otd. Akad. Nauk SSSR 8, 74 (1967); Vop. Atom. Nauk Tekh. Met. Prog. Chisl. Resh. Zad. Mat Fiz. 3, 34, (1984)] have verified the main result of the theoretical research on the limitation of perturbation growth at the ablation front, which appeared in the planar foils irradiated by laser flow in the regime of accelerated motion of the ablation front. It is shown by calculations that the growth rate γ, characterizing the perturbation growth, achieves its maximal value γm at some wave number km, which is defined by initial parameters of the problem—acceleration at the ablation front g and velocity of ablation ua. It is in good agreement qualitatively and quantitatively, with theoretical results obtained earlier by some authors. It is shown by calculations that for k>km, as it proceeds from the theory, the growth rate decreases down to zero. Simulations of turbulent mixing on the basis of the Ke model is implemented. For the thin foil case considered, an analytic estimate of the effect of turbulent mix, which included Takabe’s formula, showed ablation reduced in the coefficient in the mixing equation by a factor of 25. Theoretical and numerical research on the influence of turbulent mixing on the performance of the compressed part of the plate has been conducted.

Blood system functions are very diverse and important for most processes in human organism. One of its primary functions is matter transport among different parts of the organism including tissue supplying with oxygen, carbon dioxide excretion, drug propagation etc. Forecasting of these processes under normal conditions and in the presence of different pathologies like atherosclerosis, loss of blood, anatomical abnormalities, pathological changing in chemical transformations and others is significant issue for many physiologists. In this connection should be pointed out that global processes are of special interest as they include feedbacks and interdependences among different regions of the organism. At the modern level of computer engineering the most adequate physical model for the dynamical description of cardiovascular system is the model of non-stationary flow of incompressible fluid through the system of elastic tubes. Mechanics of such flow is described by nonlinear set of hyperbolic equations including mass and momentum conservation joined with equation of state that determines elastic properties of the tube [1]. As we interested in global processes the models of the four vascular trees (arterial and venous parts of systemic and pulmonary circulation) must be closed with heart and peripheral circulation models. Heart operation is described by the model of fluid flow averaged by volume through the system of extensible chambers that results in the set of stiff ordinary differential equations [1]. When combined these models allow us to consider functional changes and responses as during one cardiac cycle and at a longer periods upon 10 minutes that Open image in new window Fig. 1. Pressure wave propagation through the large pulmonary arteries during one cardiac cycle. Grayscale designates divergence from the minimum pressure in each vessel.

The results are presented of numerical simulations of the self‐similar problem on shear turbulent mixing of plain layers. The simulations used 2D k‐e model. The dependence was obtained of mixing zone growth rate on the layers density ratio in the incompressible limit. Influence of compressibility is also discussed.

Summary form only given. 2D radiation MHD simulations show that mass flows from separate wires join at the half of radius. To understand this phenomenon a sequence of 2D simulation runs have been done: 1) pure hydrodynamics without magnetic field and radiation transport; 2) including magnetic field; 3) including radiation transport. It is obtained that two factors plays an important role: development of hydroinstabilities (Kelvin, RT and RM) and "frozen-in" magnetic field. The "cold start" of separate wire explosion in an array has been the subject of interest in order to understand the implosion dynamics. Mass inflow dependence on initial distance between wires is analyzed. The complicated dynamic structure of exploded wire determines the mechanism of plasma entrainment from single wire towards the axis. The dense core formed at the axis of single wire is surrounded by liquid-vapor mixture with strong perturbations. Wide range equation of state accounting metastable properties and elastic-plastic properties of matter has been used. Calculations show that the mixture is the result of overheating instability. The interaction of shock wave generated by neighboring wire and media with different densities leads to MHD instabilities. Results of numerical simulation have been compared with experimental data obtained on generator ANGARA (TRINITI, Russia) and with the data calculated by using the model of delaying of plasma formation. Dependence of processes on power input rate has been estimated.