Small particles transported by a fluid medium do not necessarily have to follow the flow. We show that for a wide class of time-periodic incompressible flows inertial particles have a tendency to spontaneously align in one-dimensional dynamic coherent structures. This effect may take place for particles so small that often they would be expected to behave as passive tracers and be used in PIV measurement technique. We link the particle tendency to form one-dimensional structures to the nonlinear phenomenon of phase locking. We propose that this general mechanism is, in particular, responsible for the enigmatic formation of the "particle accumulation structures" discovered experimentally in thermocapillary flows more than a decade ago and unexplained until now.
Abstract. The study addresses the phenomenon of accumulation of rigid tracer particles suspended in a time-dependent thermocapillary flow in a liquid bridge. We report the results of the three-dimensional numerical modeling of recent experiments [1, 2] in a non-isothermal liquid column. Exact physical properties of both liquids and particles are used for the modeling. Two liquids are investigated: sodium nitrate (N aN O3) and n-decane (C10H22). The particles are modeled as perfect spheres suspended in already well developed time-dependent thermocapillary flow. The particle dynamics is described by the Maxey-Riley equation. The results of our simulations are in excellent agreement with the experimental observations. For the first time we reproduced numerically formation of the particle accumulation structure (PAS) both under gravity and under weightlessness conditions. Our analysis confirms the experimental observations that the existence of PAS depends on the strength of the flow field, on the ratio between liquid and particle density, and on the particle size.
К настоящему времени накоплен большой объём калориметрических данных о теплоте (энергии) взрыва Q различных взрывчатых веществ (ВВ) и взрывчатых составов (ВС). Получены зависимости Q от начальной плотности ВВ Q(ρ0). Однако, на практике давление детонации в основном заряде можно менять, вызывая пересжатую детонацию, за счёт инициирования основного заряда мощным ВВ, поэтому практический интерес представляют зависимости теплоты взрыва от давления детонации Q(Р), которые можно получить на основе имеющихся зависимостей Q(ρ0) для индивидуальных ВВ, распространив их на ВС. Приведена методика определения зависимостей для расчёта теплоты взрыва различных ВС, включая алюминийсодержащие, как при нормальной так и при пересжатой детонации A large volume of calorimetric data on the heat energy Q of explosion for various explosives (Es) and explosive compositions (EC) has been accumulated by now. The dependences of Q on the initial ES density Q (ρ0) are obtained. However, the detonation pressure in the base charge can be changed in practice causing super compressed detonation, due to the initiation of the base charge by a powerful explosive; therefore, the dependences of the explosion heat on the detonation pressure Q (P), which can be obtained on the basis of the available dependences Q (ρ0) for individual explosives is of practical interest as they can be applied to EC. A method to determine the dependences for calculating the heat of explosion of various aircraft, including aluminum-containing ones, both during normal and super compressed detonation is presented.
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