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Immiscible liquid–liquid flows in microchannels are used extensively in various chemical and biological lab-on-a-chip systems when it is very important to predict the expected flow pattern for a variety of fluids and channel geometries. Commonly, biological and other complex liquids express non-Newtonian properties in a dispersed phase. Features and behavior of such systems are not clear to date. In this paper, immiscible liquid–liquid flow in a T-shaped microchannel was studied by means of high-speed visualization, with an aim to reveal the shear-thinning effect on the flow patterns and slug-flow features. Three shear-thinning and three Newtonian fluids were used as dispersed phases, while Newtonian castor oil was a continuous phase. For the first time, the influence of the non-Newtonian dispersed phase on the transition from segmented to continuous flow is shown and quantitatively described. Flow-pattern maps were constructed using nondimensional complex We0.4·Oh0.6 depicting similarity in the continuous-to-segmented flow transition line. Using available experimental data, the proposed nondimensional complex is shown to be effectively applied for flow-pattern map construction when the continuous phase exhibits non-Newtonian properties as well. The models to evaluate an effective dynamic viscosity of a shear-thinning fluid are discussed. The most appropriate model of average-shear-rate estimation based on bulk velocity was chosen and applied to evaluate an effective dynamic viscosity of a shear-thinning fluid. For a slug flow, it was found that in the case of shear-thinning dispersed phase at low flow rates of both phases, a jetting regime of slug formation was established, leading to a dramatic increase in slug length.

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Проведено расчетно-экспериментальное исследование снарядного режима течения смеси касторового и парафинового масел в микроканале Т-типа с поперечными размерами канала 200×400 мкм. Определен диапазон существования снарядного режима течения. Установлена зависимость длины снарядов парафинового масла от отношения расходов жидкостей. Проведено сравнение расчетных и экспериментальных данных. Показано хорошее согласие расчета и эксперимента. В последнее десятилетие наблюдется существенный интерес к двухфазным течениям в микроканалах. Течение несмешивающихся жидкостей в микроканалах используются для производства эмульсий, синтеза наноматериалов, проведения реакций нитрования и экстракции. Перспективным направлением является также развитие капельных микрореакторов для биомедицинских приложений [1], производительность которых может быть на порядки увеличена по сравнению с традиционными системами. Двухкомпонентные потоки жидкость-жидкость в микроканалах характеризуются набором различных режимов течений [2-4]. Эти режимы обусловлены балансом сил инерции, вязкого трения и межфазного взаимодействия, которые как правило преобладают над силами гравитации из-за малых характерных размеров канала. Такой режим течения как

The parameters of the equivalent central dipole calculated using hourly values of the magnetic field elements during 2011: the angular elements transformed to the hourly values of the geographic coordinates of the North magnetic pole and the intensity values transformed to local magnetic constant. Next step is the calculation of the daily mean values at every hour. This method applied to both current digital data and historical data presented as monthly tables of hourly values. The advantage of method is its ability to show the changes of the magnetic field independently from daily variation. Using of the “integrate” parameters (the magnetic pole coordinates and local magneto constant) allows detect the regional features of its variations. The features in the daily values compared with anomalous geological and geophysical events observed in the past and predicted in the near future.