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DOI 10.21662
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Gumerov I.I., Katashova A.A., Yulmukhametova Y.V. Collapsing motions of a diatomic gas whose density depends only on time. Multiphase Systems. 18 (2023) 1. 9–16 (in Russian).
2023. Vol. 18. Issue 1, Pp. 9–16
DOI: 10.21662/mfs2023.1.002
Collapsing motions of a diatomic gas whose density depends only on time
Gumerov I.I., Katashova A.A., Yulmukhametova Y.V.∗∗
Ufa University of Science and Technology, Ufa, Russia
∗∗Mavlyutov Institute of Mechanics UFRC RAS, Ufa, Russia


One submodel of gas motion with a linear velocity field is considered in the paper. Namely, a submodel that defines the movements of a polytropic gas with a density that depends only on time. A polytropic gas is a gas for which the internal energy is a function linear in temperature. The submodel under consideration is given by a system of ordinary differential equations of the 22nd order for unknown functions. These functions characterize the movements of gas particles and determine the type of density, pressure and entropy functions. The exact solution is sought for a special case, namely for a diagonal linearity matrix. Two new exact solutions have been found. The type of vector functions of velocity, density and pressure are determined. By the form of the velocity function, the world lines of motion of gas particles are recorded. In the three-dimensional space of coordinates x, y, z, the trajectories of gas particles for various initial data are constructed. A qualitative analysis of the movement was carried out. The Jacobi matrix is constructed. The moments of collapse of gas particles are determined by the value of the Jacobian. Both solutions have collapse: collapse on a straight line and collapse at a point.


polytropic gas,
diatomic gas,
linear velocity field,
inhomogeneous deformation,
trajectories of gas particles,
world lines of particle motion,

Article outline

Objective: to find and study new exact solutions to the equations of gas dynamics with a linear velocity field and time-dependent density.

Methods: The following approach was chosen to find new exact solutions. The linearity matrix is selected in a diagonal form with several identical elements. After substituting such a solution into the ordinary differential equations of the model, the form of these matrix elements is determined.

Result: The type of the linearity matrix allowed us to determine the type of all gas-dynamic functions. Velocity, density, pressure and entropy.


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