VNIIEF CODES AND METHODS FOR THE CALCULATION OF 2-D AND 3-D NONSTATIONARY RADIANT ENERGY TRANSFER IN COMPLEX SHAPE REGIONS USING THE VISIBILITY COEFFICIENTS. CONVERSION APPLICATIONS PROBLEMS

Ju. N. Babaev, S. V. Bazhenov, A. A. Bazin, E. G. Vasina, V. V. Gorev, Yu. A. Dementiev, V. G. Zagrafov, E. A. Karpovtsev, A. I. Kirillov, V. F. Mironova, P. I. Pevnaya, P. A. Perepelkin, G. I. Skidan, I. D. Sofronov, B. P. Tikhomirov, E. N. Tikhomirova, N. I. Yurina
VANT. Ser.: Mat. Mod. Fiz. Proc.. 1995. No 4. P. 3-8.

      The paper briefly reviews the codes and methods resulting from many years of experience in the calculation of nonstationary radiant energy transfer using the visibility coefficients.
      The visibility coefficients determine the geometrical transfer factors; their direct use in the computational schemes allows to increase the description accuracy of the angular distribution of the radiation energy, to account for the solution smoothness discontinuities and derivatives.
      The capability for solving the problems in complex shape regions can make useful the conversion variants of codes in engineering and research computations in the fields such as development of infrared and neutron emitters, optimization of radiant heating and energy transfer in outer space, computer graphics.
      Actually there is an increased interest to the use of the visibility coefficients and authors believe it will further increase in view of the evolution of nanosecond technologies.

O. I. Morozov
VANT. Ser.: Mat. Mod. Fiz. Proc.. 1995. No 4. P. 9-11.

      The exact solutions are obtained for the equations of polytropic gas dynamics for 1 D, 2-D and 3-D flows; the solutions are invariant to the extension symmetries and some weak symmetries.

A. M. Buyko, V. M. Danov, V. I. Mamyshev, V. B. Yakubov
VANT. Ser.: Mat. Mod. Fiz. Proc.. 1995. No 4. P. 12-18.

      Setting up numerical computations of an explosive-magnetic system used in electrophysical experiments in high energy density physics (liner experiments, pulsed thermonuclear fusion, etc.) is described. Governing equations and boundary conditions are given which model operation of the disk electromagnetic generator, the electro-exploded foil fuze opening switch, the liner ponderomotive unit and the transmission lines connecting system elements. A scheme is given for consistent solution of these equations implemented in a program complex for numerical computations on SVS type computers.
      Detailed accounting for the design of the system under consideration, the mode of its operation and using, as a rule, general physical characteristics of materials used such as equations of state, conductivity etc., are suggested. The technique allows to predict temporal dependencies of currents, voltages and other system characteristics within the accuracy order of these charac-teristics measured in the experiments.

Yu. A. Bondarenko
VANT. Ser.: Mat. Mod. Fiz. Proc.. 1995. No 4. P. 19-23.

      A new approach is proposed to the approximation of internal energy equation in difference Krest-type schemes for 1-D and multidimensional gas dynamics so that the resulting difference scheme conserves the total energy with positively defined kinetic energy. In the new difference scheme the internal energy equation is split into two equations. The total energy is conserved even when iterations did not converge during the calculation of the difference equation for the internal energy. The total energy is also conserved when heat conduction and energy sources are separated from gas dynamics.

V. V. Dolgov, M. V. Kascheev, Yu. V. Muranov
VANT. Ser.: Mat. Mod. Fiz. Proc.. 1995. No 4. P. 24-36.

      This paper presents two versions of nuclear reactor vessel melting model with one of the possible severe accident scenario imitation. The description of heat transfer, mass transfer and hydrodynamic in cylindrical coordinates for two phase heating environment is given. Steel wall melting and dissolution conditions are formulated. The two-dimensional axisymmetrical and one-dimensional mathematical models are the working versions of the model described above. The implicit method ot Navier-Stokes equations solution in primitive variables has been used. The results of calculation of corium interaction with reactor vessel are presented.

L. I. Rubina
VANT. Ser.: Mat. Mod. Fiz. Proc.. 1995. No 4. P. 37-41.

      An algorithm is described for the exact solution of the problem in generating geometrically optimal 3-D meshes for one class of regions formed by unrolling surfaces. The examples are given for the regions and meshes demonstrating how the variation of free parameters (dihedral angles between the surfaces, their average curvatures, edge rotation etc.) influences the region shapes and mesh quality.
      The quality criteria are proposed for 3-D meshes.
      Partial examples of regions and optimal meshes can serve the tests for the quality estimation of the meshes generated with other algorithms.

A. Yu. Artemiev, V. I. Delov, L. V. Dmitrieva, I. D. Sofronov, Yu. D. Chernyshev
VANT. Ser.: Mat. Mod. Fiz. Proc.. 1995. No 4. P. 42-47.

      The paper considers unlimited adiabatic compression of gas regions with prism and cone shapes for which the exact, and approximate solutions are obtained by A.F. Sidorov. The discussion is given for the formulation in Lagrangian variables.
      Brief characteristics are given for Lagrangian D method using regular grid that was used for numerical simulation of gas compression.
      The numerical results are presented allowing to estimate the feasibility of numerical research for dense and fast jets with D code by comparing with analytical and approximate solutions. The numerical solutions are obtained by setting the velocity and pressure on a moving flexible piston.