


Vol 62, No 12 (2017)
- Year: 2017
- Articles: 9
- URL: https://journals.rcsi.science/1028-3358/issue/view/12061
Mechanics
Flow-around modes for a rhomboid wing with a stall vortex in the shock layer
Abstract
The results of theoretical and experimental investigation of an asymmetrical hypersonic flow around a V-shaped wing with the opening angle larger than π on the modes with attached shockwaves on forward edges, when the stall flow is implemented on the leeward wing cantilever behind the kink point of the cross contour. In this case, a vortex of nonviscous nature is formed in which the velocities on the sphere exceeding the speed of sound and resulting in the occurrence of pressure shocks with an intensity sufficient for the separation of the turbulent boundary layer take place in the reverse flow according to the calculations within the framework of the ideal gas. It is experimentally established that a separation boundary layer can exist in the reverse flow, and its structure is subject to the laws inherent to the reverse flow in the separation region of the turbulent boundary layer arising in the supersonic conic flow under the action of a shockwave incident to the boundary layer.



Watt regulator dynamics
Abstract
The nonlinear problem on Watt regulator motion mounted on a machine subjected to set vertical harmonic small-amplitude vibrations is considered. The problem on the existence and stability of the periodic motions of the regulator is investigated by the methods of the classical perturbation theory and the Kolmogorov‒Arnold‒Moser (KAM) theory. Under additional assumptions that the regulated-machine vibrations are high-frequency, an integrable approximate set of equations is obtained and it is shown that the majority of its trajectories are retained also in the complete set.



Modeling the angular motion dynamics of spacecraft with a magnetic attitude control system based on experimental studies and dynamic similarity
Abstract
The problem of spacecraft attitude control using electromagnetic systems interacting with the Earth’s magnetic field is considered. A set of dimensionless parameters has been formed to investigate the spacecraft orientation regimes based on dynamically similar models. The results of experimental studies of small spacecraft with a magnetic attitude control system can be extrapolated to the in-orbit spacecraft motion control regimes by using the methods of the dimensional and similarity theory.



Investigation of the ignition of liquid hydrocarbon fuels with nanoadditives
Abstract
During our experimental studies we showed a high efficiency of the influence of nanoparticle additives on the stability of the ignition of hydrocarbon fuels and the stabilization of their combustion in a highfrequency high-voltage discharge. We detected the effects of a jet deceleration, an increase in the volume of the combustible mixture, and a reduction in the inflammation delay time. These effects have been estimated quantitatively by digitally processing the video frames of the ignition of a bubbled kerosene jet with 0.5% graphene nanoparticle additives and without these additives. This effect has been explained by the influence of electrodynamic processes.



Grid turbulence and its interaction with a shock wave
Abstract
Turbulent fluctuations of density and pressure in air and argon in a shock tube have been investigated as well as their interaction with a shock wave reflected from a perforated plate at the end of a shock tube. Air and argon were used as test gases. The Mach number of the incident shock was 1.9–3.9, that one of the reflected shock was 1.4–2.4. The turbulent length scale behind the incident shock was measured as well as that one behind the reflected shock. The last value is a few times less than the former. It was established that there is overpressure in the turbulent flow behind the reflected shock. The value of the overpressure is 12% in argon and 9% in air.



A pendulum on a rotating and vibrating foundation
Abstract
The motion of a pendulum is investigated in a uniform gravity field. The foundation of the pendulum is assumed to rotate around the vertical simultaneously accomplishing harmonic vibrations along it with a high frequency and small amplitude. With use of the classical perturbation theory and modern methods of analysis of nonlinear dynamical sets, the problem on the existence and stability of periodic motions of a pendulum with the period equal to that of the vibrations of the foundation is solved.



Analytical solution of the equations of the physical theory of meteors for a single (non-fragmenting) body with mass loss in a non-isothermal (arbitrary) atmosphere with a variable ablation parameter
Abstract
We have obtained an analytical solution of two simultaneous ordinary differential equations of the physical theory of meteors: the equation of motion for the center of mass of a meteoroid (deceleration equation), the thermal balance equation (ablation equation), the luminosity equation, and the ionization trail equation. The solution has been obtained by assuming a straight-line trajectory and a power-law dependence of the ablation parameter on the meteoroid velocity for an arbitrary atmosphere in the continuous flow regime.



Frequency-domain criteria for global stability of dynamic systems with the Prandtl and play operators
Abstract
The frequency criterion of the global stability of dynamic systems with the Prandtl and “play” operator is formulated. The scheme of its proof is given. The advantage of the criterion obtained as compared with the known Logemann–Ryan criterion is shown.



New invariant relations for one critical subsystem of a generalized two-field gyrostat
Abstract
In this paper new invariant relations for one critical subsystem of a completely integrable Hamiltonian system with three degrees of freedom found by V.V. Sokolov and A.V. Tsyganov, known as a generalized two-field gyrostat, are obtained. The dynamic system that is induced on the invariant four-dimensional submanifolds is almost everywhere Hamiltonian with two degrees of freedom. The type of system motions on this invariant manifold is determined.


