Interaction of long-wave disturbances of the external flow with a shock wave on a wedgeTsyryulnikov, I. S.; Poplavskaya, T. V.
2021 Thermophysics and Aeromechanics
doi: 10.1134/s0869864321010042
Relations for the coefficients of transformation of disturbances to pressure oscillations for the case of long-wave disturbances of the external flow are derived from the general analytical solution of the inviscid problem of disturbance interaction with an oblique shock wave on a wedge. Numerical simulations of interaction of long-wave disturbances with a shock wave on a flat plate aligned at an angle of attack in the interval 5°–20° for a viscous flow regime are performed. Deviations of the transformation coefficients simulated for the viscous case from the inviscid analytical solution in the long-wave approximation are calculated, and corrections for viscous-inviscid interaction in the analytical solution are obtained.
Experimental study of evolution for circular impinging micro- and macrojetsLitvinenko, Yu. A.; Litvinenko, M. A.; Zverkov, I. D.
2021 Thermophysics and Aeromechanics
doi: 10.1134/s0869864321010054
The paper describes how the acoustic impact on an impinging jet induces a maldistribution in the radial velocity field within the nearwall zone of spreading jet. The r.m.s. velocity pulsation level in the nearwall jet is lower than in the natural jet. A higher length of the laminar flow zone in a microjet was noted. The development of sinusoid-type instability facilitates a higher combustion efficiency for a propane-butane fuel mixture in the impinging microjet; this reduces the soot emission. The tests demonstrated that the zero acoustic impact makes the flame spectrum more yellow (including the flame from the nearwall zone). This testifies about deficiency of oxidizer (air) and soot presence in the combustion products. The combustion efficiency for diffusive flame in the impinging jet depends on the nozzle diameter and nozzle-target distance.
Angular momentum transfer across the interface of two immiscible liquidsSharifullin, B. R.; Naumov, I. V.
2021 Thermophysics and Aeromechanics
doi: 10.1134/s0869864321010078
The paper studies the transfer of angular momentum across the interface of two immiscible liquids in a closed vortex flow, generated in a stationary cylindrical container by a rotating disk, being the upper endwall of the cylinder. When the disk rotates, a centrifugal force begins to act on the upper less dense liquid, which leads to the appearance of a centrifugal circulation of the upper liquid. Since the swirling flow of the upper fluid along the sidewall moves from the rotating disk to the interface, it transfers the angular momentum to the interface, thereby swirling the lower fluid as a result of the action of viscous friction. A forced circulation of the lower fluid arises. Flow visualization and measurement of the circumferential velocity component serve to determine the regularities of the formation of a vortex flow of a denser liquid located under the interface and having no direct contact with the solid disk generating the vortex motion. The development of the centrifugal circulation of the lower liquid is found to be similar to that in a mono-fluid. The obtained results are of interest for further development of vortex devices and reactors that provide complex vortex motion of ingredients for mass transfer enhancement, optimization of the operation of existing units, and for the design of new devices.
Effect of gas temperature and nozzle traverse speed on the deposition efficiency in cold sprayingShikalov, V. S.; Klinkov, S. V.; Kosarev, V. F.
2021 Thermophysics and Aeromechanics
doi: 10.1134/s086986432101008x
The influence of the stagnation temperature of the accelerating gas flow and that of nozzle travel speed on the deposition efficiency are studied when depositing single Cu-coating tracks by the cold spray technique. The experiments performed clearly show that the nozzle traverse speed substantially affects the value of measured deposition efficiency: the higher is the nozzle traverse speed, the lesser the measured deposition efficiency turns out to be at all other things being identical. Such a behavior can be explained by the fact that the first impacts of particles onto the substrate do not lead to their adhering to the surface and, hence, to coating deposition. It is known that, before the coating starts to grow, it is necessary for the substrate surface to be subjected to a sufficient number of particle impacts. This preparatory stage is called the activation stage, or the delay (induction) stage of the deposition process. It is shown for the first time that the specific (per unit area) mass of the powder consumed at the activation stage depends on the stagnation temperature of the accelerating gas flow: the higher is the stagnation temperature, the lower is the specific mass consumed.
Modeling of heat transfer due to induction heating of laminated glass-metal materialsLyubimova, O. N.; Barbotko, M. A.
2021 Thermophysics and Aeromechanics
doi: 10.1134/s0869864321010091
The heat-induced variations in material properties for a layered glass-metal composite material were studied for the case of induction heating and the subsequent composite annealing of the sample. A cylindrical sample of the composite (outer metal cylinder covering the glass cylinder) was used in our experimental study. This sample is an imitation of a brittle rock under a high stress. The simulation complexity originates from superposition of the glass point transition within the glass layer, induction heating for the whole sample, and heat radiation from the external metallic surface. Structural and mechanical relaxation processes in glass are calculated using the Boltzmann-Volterra superposition and the Tula-Narayanaswami-Mazurin-Moynihan (TNMM) model based on introducing a structural temperature as an additional parameter. The paper offers a mathematical model and a simulation method for calculating the temperature field and material properties distributions during the composite production process. The simulation results are presented for various regimes of heating and for glass-metal composite properties. This approach is useful for evaluating the operation modes of the glass layer annealing and for estimating the evolution of laminated composite materials.
Numerical studies of nonstationary conjugate convective heat transfer in vertical layers of liquid and gas separated by a thin metal partitionBerdnikov, V. S.; Kislitsyn, S. A.
2021 Thermophysics and Aeromechanics
doi: 10.1134/s0869864321010108
The development of a convective flow after sudden heating of a vertical wall that laterally bounds a layer of ethyl alcohol in a system consisting of vertical layers of alcohol and air, separated by a thin metal partition, is studied numerically in a conjugate problem statement. The equations of thermogravitational convection in the Boussinesq approximation, written in variables of temperature, vortex, and stream function, are solved by the finite element method. The development of unsteady hydrodynamic and thermal boundary layers on all four vertical walls is studied. The temperature fields in liquid, gas and in a vertical partition are calculated. The features of the development of the spatial form of the flow and unsteady conjugate convective heat transfer between the layers of liquid and gas affect significantly the unsteady temperature fields and temperature gradients in a thin metal partition. The maximum temperature gradients in the partition appear at the initial stage of flow development.