Исследовалась динамика тепловых полей диэлектрических поверхностей, нагретых в результате инициирования импульсного сильноточного поверхностного разряда (плазменного листа). Генерация импульсного поверхностного разряда, скользящего по поверхности диэлектрика, происходила на верхней (плоской) и нижней (с уступом) стенках разрядной камеры с кварцевыми окнами. Получены последовательные изображения оптического (наносекундный диапазон) и инфракрасного (миллисекундный диапазон) излучений вблизи диэлектрической вставки в форме прямоугольного параллелепипеда размером 6 × 2 × 48 мм 3 . С помощью покадровой съемки в инфракрасном диапазоне зарегистрирована при давлениях от 65 до 290 Торр эволюция теплового излучения поверхностей во времени. Показано, что время остывания нагретой плазмой области, локализированной вблизи диэлектрической вставки, может длиться до 30 мс и существенно превышает время остывания плоской верхней стенки, нагретой достаточно однородно распределенным по поверхности диэлектрика разрядом.

The paper presents the results of non-stationary thermal fields panoramic visualization, based on infrared thermography at the STDO-3 device (Shock Tube -Discharge -Optics) of the Lomonosov Moscow State University, Faculty of Physics.The main purpose of the work was to study the heating and cooling processes in a rectangular channel region under the influence of pulsed surface high-current discharges sliding over the dielectric surface, taking into account the supersonic flow in a channel with an obstacle.A pulsed surface discharge initiated in a 24x48 mm2 channel was studied in a quiescent air and in a high-speed flow behind the shock.When initiated in the flow (the delay time after the shock wave passage is up to 0.4 ms), the discharge plasma is localized mainly in the downwind region behind the reverse step (rectangular ledge).The discharge produces a pulsed (submicrosecond) contracted energy input with a 30 mm length in the localization zone.As a result, there is a short-term heating of the section of the channel wall adjacent to it.Using infrared (IR) thermographic imaging through the chamber quartz windows transparent to IR radiation, it was found that in the discharge chamber the discharge plasma noticeably heats the surface of the flat channel wall.Based on the obtained data of panoramic visualization with an exposure time up from 200 µs, we studied the channel walls cooling process both in quiescent air and in flow at different oncoming gas velocities -in the downwind region behind the dielectric ledge.

The paper presents the panoramic visualization of thermal fields in the discharge section of the UTRO-3 experimental device of the Lomonosov Moscow State University Faculty of Physics. The main purpose of the work was to study the heating and cooling processes in a rectangular channel region under the influence of pulsed surface high-current discharges sliding over the dielectric surface, taking into account the supersonic flow in a channel with an obstacle structures. A pulsed surface discharge initiated in a 24x48 mm channel in a high-speed flow (the delay time after the shock wave passage is up to 0.4 ms) is localized mainly in the downwind region behind the reverse step (rectangular insert). The discharge produces a pulsed (submicrosecond) energy input with a length of 30 mm in the localization zone. As a result, there is a short-term heating of the section of the channel wall adjacent to it. Using infrared thermographic imaging through the chamber quartz windows transparent to IR radiation, it was recorded in the discharge chamber that the induced discharge plasma noticeably heats the surface of the flat channel wall. Based on the obtained data of panoramic visualization with an exposure up from 100 µs, we studied the cooling time of the channel walls in the downwind region evolution, heated rapidly due to the interaction with the surface discharge plasma, at various free flow velocities.

We report on the effect of nanosecond surface sliding discharge glow redistribution near a dielectric ledge and high-speed post-discharge flow dynamics. The discharge energy localization is shown to be supplementary to plasma glow inhomogeneity along the surface. The process is studied in a discharge chamber with two $$100 \,\mathrm{mm} \times 30 \,\mathrm{mm}$$ surface sliding discharges (plasma sheets) placed on the top and bottom walls and a dielectric ledge, $$48\,\mathrm{mm} \times 6 \,\mathrm{mm} \times 2 \,\mathrm{mm}$$ in size, mounted on the bottom plasma sheet. The dynamics of the discharge-induced flow is captured using high-speed shadowgraphy during the first 40–50 $$\mu \mathrm{s}$$ after the discharge ignition. Computational fluid dynamics (CFD) simulations of the induced flow are also conducted to gain more insight into the energy release area configuration. Based on the numerical and experimental shadow images matching, the pulsed discharge energy redistribution is quantitatively analyzed.

In this paper, we describe the phenomenon of redistribution of plasma and current of a pulsed volume discharge based on self-localization upon initiation in an unsteady flow in a shock tube with a cross section of 48 × 24 mm. In the gas-dynamic channel section with a parallelepiped-shaped ledge in the flow behind the shock wave front with Mach numbers 2.8–3.5, short-lived plasma channels were shown to be realized in the separation zones near the ledge for 2800 μs.

The phenomenon of pulsed volume discharge plasma and current redistribution based on self-localization in an unsteady flow in a shock tube with 48 x 24 mm cross section is described. It is shown that in the gas-dynamic channel with a parallelepiped-shaped step in the flow behind theshock wave with Mach numbers of 2.8 - 3.5, short-lived plasma channels are formed in the separation zones near the step within 2800 μs.

The elastocaloric effect (ECE) is studied in samples of rapidly quenched ribbons of a Ti 2 NiCu alloy at a periodic action by a mechanical stress to 300 MPa at a frequency to 50 Hz. ECE is maximal near the temperatures of a first-order thermoelastic martensitic phase transition. The ECE maximum is observed in a point corresponding to the completion of the reverse martensitic transition ( T = 67.5°C) and is 21 and 6 K at cyclic mechanical loads of 300 and 100 MPa, respectively. The ECE value is shown to be independent of the frequency of the external loads in the range from 0 to 50 Hz. The specific power of a rapidly quenched ribbon as a thermal energy transformer is estimated at the external mechanical stress of 100 MPa; its value is 150 W/g at a frequency of 50 Hz and ECE is 6 K.

The effect of laminar and turbulent boundary layers on the localization of pulsed discharge glow in gas in rest and in flow in a gasdynamic channel is studied. It is found that the glow of a discharge localized into the separation zone on a glass surface is of the form of regular structures capturing the structure of turbulent inhomogeneities in the boundary layer. The flow visualization was performed using a pulsed space discharge with UV preionization realized in a working chamber of rectangular section.

An experimental investigation of combined discharge (pulse volume discharge with preionization by plasma electrodes) was carried out: glow time and space characteristics, analysis of flow with discharge-produced blast waves. The contracted volume discharge (spatial gas discharge mode in contracted form) was considered as electrical breakdown − a 24-mm-long vertical plasma column was formed. As a result of the nanosecond-lasting breakdown, the internal energy of the gas increased and the pressure raised up, which led to the formation of gas flow with cylindrical shock (blast) waves. The flow evolution was visualized with the aid of high-speed shadowgraphy. The blast waves were recorded, their position and speed were measured; the instability of the post-discharge hot gas channel was also visualized. A two-dimensional numerical simulation of flow based on the Euler equations was performed. The model of pulse cylindrical energy deposition was used; initial conditions were taken from experimental data. An inverse problem was solved by comparing CFD with the position of experimental shock waves. It was shown that 20−22% of the combined discharge energy, stored in the capacitor, was converted into the internal gas energy (about 140-155 mJ). Shock waves from surface discharges were also visualized and analyzed.

Application of the 3D visualization method with high time resolution for investigation of gas flow past a model of an oversized cone-cylinder body is presented. The nanosecond transversal spatial discharge with plasma electrodes is used for transonic flows with shock waves visualization in a shock tube. The discharge electric current time and luminescence time is 200 ns. Flow structure details are visualized by plasma flash glow recording. The pulse discharge visualization method allowed obtaining images of local low-density areas from two different views − upwind and downwind the streamlined model. The simultaneous instant images of discharge glow were taken by two cameras through opposite windows of the test chamber. Elements of the visualized flow structure are: shock waves, separation lines, vortices in a rear separation zone, terminating discontinuity, and boundary separation zone instabilities on glass windows surface.

Nanosecond-lasting homogeneous volume discharge is tested and used for visualization and investigation of stationary and non-stationary 2D and 3D flows in shock tube channel; shock wave diffraction on models, supersonic flow over models with bow shock; transonic separation zone. Pulse volume discharge with ultraviolet preionization by radiation from the sliding surface discharges was used. Different models were tested in supersonic and transonic flow. Total time of flow glow at discharge initiating in optical band (light-emitting image exposure) was shown to be less then 150-200 ns. Gas density non-homogeneity in transonic/supersonic flow when ionized by pulse volume discharge results in redistribution of discharge plasma flux. Integral plasma glow images of instant flow structure were recorded on colour film, black-and-white film, CCD and digital photo camera.

The pulse ionization of the time-dependent quasi-two-dimensional flow developed during diffraction of a shock wave on a wedge is investigated experimentally. The redistribution of the pulse volume discharge plasma subjected to preionization by ultraviolet radiation from plasma sheets is investigated when the discharge is initiated in different stages of the time-dependent gas dynamic flow. Images of the plasma flow are compared with the corresponding fields of the gas dynamic flow parameters. It is shown that the pulse discharge plasma flows can be controlled due to the phenomenon of self-localization in a given flow zone of known shape. The local energy supply to the gasdynamic flow is simulated numerically using the experimental data.

The interaction between a pulsed volume discharge with preionization by ultraviolet radiation from plasma sheets and a gasdynamic flow with a known density distribution is studied experimentally. The complex quasi-two-dimensional flow that emerges after the diffraction of a plane shock wave by rectangular obstacles in the channel is experimentally studied and numerically simulated. The glow intensity fields for an unsteady gasdynamic flow are imaged for the first time when recording the plasma radiation from a pulsed discharge in the flow. Since the ionization duration is short (150–200 ns), the gas-flow structure does not change and the flow does not heat up in the glow time of the discharge plasma in the flow. Our images are compared with the reciprocal-density fields of the corresponding two-dimensional gas flow. The effects of gasdynamic structures on the discharge plasma redistribution in the flow are analyzed. The energy contribution is localized into low-density zones (vortices, rarefaction waves) and into regions of density jumps and significant density gradients. The discharge current from adjacent regions with low E/N is redistributed into these zones. Breakdown channels are formed along rarefaction waves, vortices, and discontinuity surfaces between high-electron-density regions.