The paper is a summary of experimental studies of water droplet breakup in the flow behind the shock wave in the range of gas flow velocities 40 ≤ U ≤ 175 m/s. A change between two different mechanisms of stripping breakup of the droplet occurs in this range of velocities, with domination of the inertia force in the case of droplet deformation and viscous friction force in the case of boundary layer shedding. The analysis of the change in the breakup mechanisms is based on a vast pool of observations and quantitative data on droplet dynamics and delays of its breakup obtained by a high-speed method of visualization with a stroboscopic laser source of light. A physical model of the process is constructed on the basis of experimental data and results of the parametric analysis, and criteria of the change in stripping mechanisms of droplet breakup are derived.

The efficiency of fluid atomization by an atomizer is studied as a function of the spray energy. The dependence of the maximum values of energy on the fluid flow rate is analyzed. A linear dependence is obtained for flow rates smaller than 80 g/s, which testifies to a high efficiency of fluid atomization. For flow rates greater than 80 g/s, the droplet energy is seen to decrease drastically, leading to an increase in the spray droplet size, which shows that the atomization quality is deteriorated. This behavior is observed in all regimes considered in the study.

Supersonic gas-liquid jets of a coaxial atomizer at high liquid concentrations are studied experimentally. A complex of optical techniques is used for studying the droplet sizes: visualization and particle image velocimetry, laser Doppler anemometry, and Malvern Spraytec instrument. The research shows that the velocity and concentration profiles change with flow rate growth: an extended region with small droplet velocities appears behind the bow shock wave; in this case, the concentration decreases significantly slower than that at low liquid flow rates. A small increase in the jet energy at liquid flow rates greater than 100 l/h and a noticeable increase in the droplet size testify that the gas jet capabilities for breaking up the liquid in the described regimes are exhausted.

Путем медленного охлаждения расплавов получены монокристаллы (Pb0.86Sr0.14)5Ge3O11. Изучено влияние облучения высокоэнергетическими электронами флюенсами до 6.2×1018э/cм2 на структурные и диэлектрические свойства этих кристаллов. Изучена зависимость параметров кристаллической структуры от величины флюенсов, установлен структурный механизм избирательного замещения Pb на Sr. Найдено, что позиции свинца с неподеленной парой электронов остаются свободными от замещения катионами стронция. Вплоть до флюэнса 6.2×1018э/cм2 структура (Pb0.86Sr0.14)5Ge3O11 сохраняет совершенство. Показано, что облучение данными флюенсами сохраняет параэлектрическую структуру при 293К (пр. гр. P) и приводит лишь к незначительным изменениям атомных смещений. Характер температурных зависимостей диэлектрических проницаемости и потерь (в интервалах 5-300 K и 1-1000 кГц) указывает, что облучение сопровождается как смещением ТС от 158 K до 145 K, так и усилением размытия сегнетоэлектрического фазового перехода.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Stoichiometric single crystals of Pb 5 (Ge 1– х Si x ) 3 O 11 solid solutions (0 ≤ x ≤ 0.55) are obtained by slow cooling of 5PbO·3(1– y )GeO 2 ·3 y SiO 2 melts. The chemical analysis confirms their cation and anion stoichiometry. The effect of their high-energy (10 MeV) electron irradiation with fluences from 0.1·10 18 e/cm 2 to 4.39·10 18 e/cm 2 on the structural, ferroelectric, and nonlinear optical characteristics of the crystals is studied for the first time. The dependence of crystals on concentrations and fluences is detected. According to the date of dielectric spectroscopy and second harmonic generation of laser radiation, the doping with Si causes a systematic shift of T c to low temperatures, a decrease in the peak value of the dielectric permittivity, and a noticeable phase transition smearing with transforming to the zelaxor ferrollectric state of x = 0.35. According to the structural studies of initial and irradiared, Pb 5 (Ge 1– x Si x ) 3 O 11 crystals, they retain the structural perfectness without any signs of amorphization. Structural distortions of Pb 5 (Ge 1– x Si x ) 3 O 11 do not significantly depend on the fluence.

влияние облучения высокоэнергетическими электронами на структурные, диэлектрические и нелинейно-оптические свойства монокристаллов твердых растворов pb5(ge1-хsix)3o11 (0≤x≤0.55) (готовится к публикации)

The goal of the study is to investigate the gas-dynamic structure of a supersonic underexpanded jet in the presence of a liquid spray as applied to the topic of gas-liquid nozzles. The wave structure is detected by methods of shadowgraphy and AVT visualization. Laser Doppler anemometry is used to measure the spray velocity and also to determine its concentration and droplet size. It is found that the flow in the two-phase core is qualitatively different from the gas jet flow. The transformation of the Mach disk in a wide range of gas flow regimes and liquid flow rates is studied. A crucial role of the gradient region of the jet in the vicinity of the Mach disk in the process of liquid atomization is demonstrated.

The problem of motion dynamics of two particles in a supersonic flow behind an incident shock wave was considered numerically and experimentally. The experiments were carried out in a shock tube. High-speed shadowgraphy with a laser stroboscope light source was used. The mathematical model was based on the two-dimensional Euler equations. The original, highly scalable, parallel algorithm of the Cartesian grid method for simulation of flows with shock waves in areas with changing geometry was used in the numerical simulations. The main stages of the process were described from the point of view of the realized shock-wave configurations. The effect of changing two modes of supersonic flow around two particles was obtained. The experimental and simulated flow patterns and dynamics of particle motion correlate well.

Совершенные стехиометрические монокристаллы Pb5Ge3O11 подвергнуты радиационному облучению g-квантами 60Co (1·106 Рад) и высокоэнергетическими электронами (0.13, 0.89, 2.18, 3.07·1018 э/cм2) в НИФХИ им. Л.Я. Карпова. прослежено изменение структурных и сегнетоэлектрических свойств кристаллов в зависимости от типа и дозы облучения. Методы диэлектрической спектроскопии и генерации второй гармоники лазерного излучения использованы для определения температуры сегнетоэлектрического фазового перехода TС. Рентгенодифракционные эксперименты проведены на дифрактометре Bruker D8 QUEST с детектором PHOTON-II (MoKα излучение, 295 K). По экспериментальным структурным амплитудам расшифрована и уточнена кристаллическая структура кристаллов до и после облучения. Структурные характеристики необлученного кристалла находятся в удовлетворительном согласии с имеющимися опубликованными данными при достигнутом существенном улучшении их точности (R(F > 2σ(F)) = 0.028). Несмотря на внесенные радиационные дефекты, монокристаллы Pb5Ge3O11 сохраняют кристаллическое строение и сегнетоэлектрические свойства. Показано, что проведенное облучение сохраняет полярную структуру при 295 K, но приводит к изменениям атомных смещений отдельных атомов. Сделано предположение, что радиационно-индуцированное изменение структуры Pb5Ge3O11 проходит по высокотемпературному типу, формируя новое структурное состояние, приближающееся к высокотемпературной модификации необлученного кристалла Pb5Ge3O11. Облучение приводит к постепенному уменьшению искажений и симметризации структуры. Существенно то обстоятельство, что кинетика и конечные продукты этих процессов значительно отличаются от таковых наблюдаемых только при термических воздействиях. Проведены расчеты величин полярных смещений, и их зависимость от дозы облучения указывает на тенденцию уменьшения полярных смещений в сегнетоэлектрике германате свинца под воздействием облучения.

The work is devoted to comparative analyzing the plume structure of gas-liquid mixture generated by nozzles of different performances. Pneumatic coaxial atomizers with outer mixing, differing 10 times in size, were investigated. Analysis of visualization results and droplet sizes data shows geometrical similarity of two-phase core of the jets of nozzles with different scales and their general resemblance regarding spray dispersion. A structure was found that makes it difficult to visualize the liquid jet in the vicinity of the nozzle exit, its nature is shown, and the mechanism of formation with an increase in gas pressure is investigated.

The temporal characteristics of the processes of deformation and disintegration of a freely falling drop of a low-viscosity liquid in an air accelerating flow are studied. The experiments were carried out under fast loading and in the regime of impulse-quasi-static loading of drops at moderate gradients of flow velocity. Experimental values of the interaction time and the induction time of the drop breakup are obtained.

Perfect stoichiometric Pb 5 Ge 3 O 11 single crystals are irradiated with 60 Co γ-rays (1·10 6 Rad) and high-energy electrons (0.13 e/cm 2 , 0.89 e/cm 2 , 2.18 e/cm 2 , 3.07·10 18 e/cm 2 ) at the Karpov Institute of Physical Chemistry. Changes in the structural and ferroelectric properties of the crystals are traced depending on the irradiation type and dose. Dielectric spectroscopy and second harmonic generation of laser radiation are used to determine the ferroelectric phase transition temperature T С . X-ray diffraction experiments are carried out on a Bruker D8 QUEST diffractometer with a PHOTON-II detector (Mo K α radiation, 295 K). Based on the experimental structural amplitudes the crystal structures of the crystals before and after irradiation are solved and refined. Structural characteristics of the non-irradiated crystal are consistent with the previously reported data at the achieved significant improvement of their accuracy ( R ( F > 2σ( F )) = 0.028). Despite radiation defects introduced, Pb 5 Ge 3 O 11 single crystals retain the crystal structure and ferroelectric properties. It is shown that irradiation performed maintains the polar structure at 295 K and causes changes in atomic displacements of separate atoms. It is supposed that a radiation-induced change in the Pb 5 Ge 3 O 11 structure is of the high-temperature type and forms a new structural state close to a high-temperature modification of a non-irradiated Pb 5 Ge 3 O 11 crystal. Irradiation leads to a gradual decrease in distortions and structure symmetrization. It is important that the kinetics and final products of these processes appreciably differ from those observed only upon thermal impacts. Polar shifts are calculated, and their dependence on the irradiation dose indicates a tendency to a decrease in polar shifts in lead germanate ferroelectric during irradiation.