Published in Sarov (Arzamas-16), Nizhegorodskaya oblast
NUCLEAR CENTER -
ALL-RUSSIAN RESEARCH INSTITUTE
OF EXPERIMENTAL PHYSICS
Русский | English
Issue No 3, 2015
EFFECT OF THE WAY TO ACCOUNT FOR HEAT TRANSFER ON THE CALCULATION STABILITY OF TWO-PHASE GAS-DYNAMIC DIFFERENCE SCHEME
The two-phase difference gas-dynamic scheme in Lagrangian variables is studied with account for heat transfer. We have discovered that the conditions for the Courant-type time-step strongly depend on the way the implicit heat conductivity is used in the difference scheme. In major cases the condition of stability is determined by the isentropic speed of sound. We offer a modification with account for the implicit heat conductivity in two energy equations. Continuous transition from the isentropic speed of sound to the isothermal one at the Courant thermal number increase is present in the conditions of the modified scheme stability.
VANT. Ser.: Mat. Mod. Fiz. Proc. 2015. No 3. P. 3-19.
The isothermal speed of sound is always less than the isentropic one, and when the radiation pressure is taken into account in the case of low densities and high temperatures, it can be several tens and hundreds times smaller than the isentropic one. Therefore in the modified scheme, with big Courant number, the time stem can increase significantly.
Key words: gas dynamics with thermal conductivity, difference schemes, splitting in terms of physical processes, difference scheme stability, isentropic speed of sound, isothermal speed of sound, thermal sound dispersion.
|SPECIFICS OF THE SIMPLE ALGORITHM APPLICATION FOR THE CALCULATION OF INCOMPRESSIBLE FLOWS
N. V. Tarasova, A. S. Kozelkov, D. P. Meleshkina, A. V. Lashkin, O. V. Denisova, M. A. SizovaThis paper focuses on the description of the SIMPLE algorithm modification for the case of uncompressible flows and the applicability of the implemented algorithm for the calculation of transonic compressible flows within the LOGOS program package. The problems about flow over an airfoil and inside a diffuser are used to demonstrate the capabilities of the implemented algorithm in terms of reaching acceptable accuracy and convergence velocity when various schemes of convective component discretization are used and other computational parameters are changed. The obtained results are compared with the data of well known experimental tests.
VANT. Ser.: Mat. Mod. Fiz. Proc. 2015. No 3. P. 20-34.
Key words: SIMPLE algorithm, incompressible transonic flows, schemes of convective component discretization, LOGOS program package.
|SEAMING POLYGONAL UNSTRUCTURED GRIDS IN THE "TIM-3D" TECHNIQUE
I. V. Sobolev, A. V. ShuryginThe paper describes in detail the algorithm that realizes the method of seaming polygonal unstructured grids. This method is realized within the program for initial data calculation in the TIM-3D technique. The method applicability is shown on the examples of seaming various types of grids into a single computational grid of a domain. The performance of the algorithm that seams the 3D grids is studied.
VANT. Ser.: Mat. Mod. Fiz. Proc. 2015. No 3. P. 35-45.
Key words: TIM-3D technique, unstructured polygonal grids, seaming method, TIM-RND, LOGOS-Prepost.
|ON A MODE OF IDEAL GAS PLANAR LAYER EXPANSION INTO VACUUM
V. E. Shemarulin, S. S. L'vova, Yu. V. YanilkinWe have discovered and investigated in detail the class of exact solutions of the gas dynamic equations that describe the isentropic ideal gas expansion into vacuum, when the gas fills a finite-thickness plane layer, in the case of specifically preset initial distributions of gas-dynamic parameters at the adiabatic index of 3.
VANT. Ser.: Mat. Mod. Fiz. Proc. 2015. No 3. P. 46-63.
As an example, the particular case with the zero gas initial velocity, while the initial density velocity, in accordance with quadratic law, turns into zero on the gas-vacuum interface. Characteristic features of the solution and its connection with the Legendre polynomial are highlighted. The obtained particular solution can be used for testing the techniques and programs for numerical solving the gas dynamics problems. The following specifics of a numerical method can be checked when this solution is used as a test: degree of the entropy preservation in isentropic flows, accuracy of the flows description in the vicinity of weak and strong discontinuities on the vacuum interfaces. Additional information on the numerical method accuracy can be obtained by the verification of main quality properties of exact solutions in numerical solution: immobility of sound points (weak discontinuity points), immobility of flow boundaries up to the known time, vacuum line movements (gradient catastrophe curves) under the known law.
The results of the numerical solution for the problem in question obtained with the EGAK technique are presented.
Key words: 1D gas dynamics equations, ideal gas, isentropic expansion into vacuum, exact solutions, numerical solution.
|MODELING OF RADIATION DEFECT ACCUMULATION IN PURE MOLYBDENUM USING THE METHODS OF KINETIC THEORY AND CLASTER DYNAMICS
M. Yu. Romashka, A. V. YanilkinThe modeling of radiation defect accumulation in thin pure molybdenum films under the effect of ion radiation was studied. Two approaches to the modeling were used: kinetic theory with mean cluster size and cluster dynamics.
VANT. Ser.: Mat. Mod. Fiz. Proc. 2015. No 3. P. 64-75.
The paper discusses the limitation of the first approach applicability. It can be inapplicable in the cases when defect clusters are generated in the cascades of atom shifts and the cluster diffusion to the drains, such as the surface, intergrain surfaces and dislocations, is present. This is due to the fact, that it is impossible to take into account the cluster distribution by size in the frames of the kinetic theory and to assign personal diffusion coefficients to each cluster size.
In the case of cluster dynamics the obtained results are in good agreement both with the experiment and the calculations by other authors. At that the proposed method of cluster dynamics realization differs from those used before: a stochastic approach to the cluster dynamics based on the SPPARKS code is implemented. The advantages of the stochastic approach are such as the algorithm simplicity, simplicity of reactions setting in SPPARKS, as well as high stability as compared to the standard approach, where the system of big amount of differential equations is solved. The main drawback of the approach is the limited reagent concentrations at the bottom.
Key words: kinetic theory, cluster dynamics, ion irradiation, thin films, molybdenum, point defects, SPPARKS.
|MULTITORUS TOPOLOGY FOR HIGH PERFORMANCE AND FAULT-SAFE COMMUNICATION NETWORK WITH THE SMPO-10G ARCHITECHTURE
V. G. Basalov, D. O. Kozlov, A. A. KholostovThe paper includes the multitorus topology for the communication network based on the system of itnerprocessor exchanges SMPO-10G. The paper describes the adaptive routing algorithms developed specially for this topology, which enable building the shortest and free-from-dead-ends message transmission routs, as well as providing high fault tolerance of the communication network and its balanced load.
VANT. Ser.: Mat. Mod. Fiz. Proc. 2015. No 3. P. 76-84.
Key words: multiprocessor computation complex, communication network, SMPO-10GA-1 hardware module, СМПО-10GA-AD adapter unit, СМПО-10GA-SW switch unit, adaptive routing algorithms, processor node, virtual channel.
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