Numerical investigation of some gas dynamics problems by net-characteristic method

A modification of the adaptive artificial viscosity (AAV) method is considered. This modification is based on one stage time approximation and is adopted to calculation of gasdynamics problems on unstructured grids with an arbitrary type of grid elements. The proposed numerical method has simplified logic, better performance and parallel efficiency compared to the implementation of the original AAV method. Computer experiments evidence the robustness and convergence of the method to difference solution.

Download Full-text

Оne-dimensional gas dynamics problems and their solution based on high-resolution finite difference schemes

Scientific and technical journal of information technologies mechanics and optics ◽

10.17586/2226-1494-2015-15-4-731-740 ◽

2015 ◽

pp. 731-740 ◽

Cited By ~ 2

Author(s):

P.V. Bulat ◽

K.N. Volkov

Keyword(s):

High Resolution ◽

Finite Difference ◽

Gas Dynamics ◽

Difference Schemes ◽

Finite Difference Schemes ◽

Gas Dynamics Problems ◽

Dynamics Problems

Download Full-text

Investigation of the influence of boundary conditions in the numerical solution of a vortex tube model

Multiphase Systems ◽

10.21662/mfs2019.2.013 ◽

2019 ◽

Vol 14 (2) ◽

pp. 89-100

Author(s):

M.R. Minibaev ◽

C.I. Mikhaylenko

Keyword(s):

Boundary Conditions ◽

Turbulent Flows ◽

Gas Dynamics ◽

Vortex Tube ◽

Computational Simulation ◽

Ideal Gas ◽

Tube Model ◽

Gas Dynamics Problems ◽

Dynamics Problems ◽

Physical Quantities

The applicability of various boundary conditions in the computational simulation of a Ranque–Hilsch vortex tube is investigated. A review of existing works on the effect of geometry and various thermodynamic parameters on the efficiency of the pipe is made. The substantiation of the possibility of introducing additional computational domains when moving the boundaries to study the influence of boundary conditions when modeling gas dynamics problems is given. To simulate the dynamics of a gas in a vortex tube, a mathematical model is written that includes the Navier–Stokes system of equations describing a compressible viscous fluid, which is closed by the equation of state of an ideal gas. Existing methods for calculating turbulent flows are considered. The applicability of various semi-empirical models of turbulence for modeling a vortex tube is described. The possibility of using the selected k−ε model and its description is argued. The boundary conditions characteristic of the vortex tube model are described, and the boundary conditions most combined in the simulation of gas dynamics problems are also shown. Presents a grid that takes into account the area formed by the removal of boundaries. The solution is based on the sonicFoam algorithm in the OpenFOAM package. Utilities of the postprocessor are used when preparing the model for calculations on a high-performance cluster and utilities for averaging the obtained physical quantities. The simulation results for different combinations of boundary conditions and models with remote boundaries are given. Comparison of the results obtained. It is shown that the geometrical dimensions have a strong influence on the operation of the pipe; the correct choice of boundary conditions makes it possible to obtain the values of physical quantities that are closest to the known experimental ones. Moving the boundaries away from direct exits provides an opportunity to more accurately estimate the effects that arise near the real boundaries of the vortex tube, especially affecting the magnitude of the Ranque–Hilsch effect.

Download Full-text

Modeling of Surface’s Micro- And Nanostructures for Solving of Gas Dynamics, Heat And Mass Transfer Problems

Geometry & Graphics ◽

10.12737/article_5b55a695093294.45142608 ◽

2018 ◽

Vol 6 (2) ◽

pp. 94-99

Author(s):

Ю. Брылкин ◽

Yuriy Brylkin

Keyword(s):

Gas Dynamics ◽

Geometric Model ◽

Fractal Theory ◽

Rigid Bodies ◽

Mathematical Tool ◽

Surface Geometry ◽

High Enthalpy ◽

Gas Dynamics Problems ◽

Heat Shielding ◽

Dynamics Problems

This paper is devoted to the problem of modeling a rough surface to ensure calculations for a flow around aircraft by high-enthalpy gas. The surface layer’s geometric characteristics along with the material’s chemical composition affect the surface’s optical indices and catalytic properties, and, consequently, on the measured heat flux. The problem of construction a geometric model for micro-surface has both fundamental and applied aspects. The fundamental nature stems from the fact that considered processes arising from the interaction of gas atoms and molecules with the surface are very complex ones. In such a case the correct interpretation for results of aircraft fragments’ ground experimental method is required. The work’s applied significance is determined by the need to optimize tools for flows diagnostic in high-enthalpy installations, in which simulation of thermal load affecting the aircraft in flight is taking place, as well as simulation of technological processes for heat-shielding materials and coatings development. Effective way for modeling of undifferentiated surfaces for gas dynamics problems solving is the use of fractal methods accounting the roughness at the micro- and nano-scale. They are based on the assertion that the natural surface’s structure has the same fractality at all levels. The development of this hypothesis has led to the emergence of a whole direction – material engineering – allowing most adequately describe self-organizing structures. Also, with the development of nanotechnologies, fractal geometry has found its own place in solving problems related to obtaining certain materials properties. As has been shown in the paper, fractal theory is a good mathematical tool for study of rigid bodies’ surface geometry and mechanisms influencing on the obtaining surface structure.

Download Full-text

On Some Unsolved Problems of Mathematica

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.205 ◽

2012 ◽

Vol 2 (4) ◽

pp. 259-264

Author(s):

E. V. Vorozhtsov

Keyword(s):

Gas Dynamics ◽

Software Package ◽

Two Dimensional ◽

Fortran Code ◽

Gas Dynamics Problems ◽

Dynamics Problems ◽

Mathematica Software ◽

Alternate Routes ◽

Computing Speed

In this paper, some unsolved problems of the Mathematica software package are documented. At first, it is shown, using a number of examples, that the processing (simplification) of rational-fractional expressions involving powers in the general form, has been implemented in Maple more carefully than in Mathematica. Then, an error in Mathematica is demonstrated, leading to incorrect results at a change of a function’s body. For each example of symbolic or symbolic-numeric computations, alternate routes for solving the emerged problem are proposed (where possible). An added problem, related to Mathematica’s computing speed is documented, employing examples related to two-dimensional gas dynamics problems. It is shown that Mathematica computes rather slowly (about one thousand times slower) compared to a Fortran code.

Download Full-text