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• Traditional calculation method of sand carrying speed is inefficient. • The proposed method fully considers the temperature and high sand carrying rate. • Double correction coefficients are used to correct the drag coefficient. Formation sand production is an important engineering and technical problem that restricts the safe and efficient development of geothermal wells. Accurate prediction of the minimum sand carrying velocity of sand production is the key to effectively controlling the formation sand production of geothermal wells. Compared with conventional vertical well sand production, geothermal wellbore sand carrying has the characteristics of high concentration, high fluid temperature, and easy silting, which makes it more difficult to calculate the minimum sand carrying velocity. In order to derive the formula of sand carrying law suitable for complex geothermal conditions, this paper considers the temperature and concentration conditions, based on the basic sedimentation principle and indoor sand carrying experiment, abandons the single correction coefficient correction of the conventional calculation formula, integrates the influence of temperature and high sand content on debris migration and deposition, and adopts the double correction coefficient of temperature-viscosity and sand content-mixed density, the actual minimum sand carrying velocity calculation formula of geothermal well under different sand content and temperature is obtained, and a new theoretical calculation method of minimum sand carrying velocity of the geothermal wellbore is formed. With the help of indoor experiments, a reasonable experimental group was designed to carry sand law experimental research. The experimental results show that the calculated value is in good agreement with the measured data, and can be used to calculate the minimum sand-carrying velocity of unconsolidated sandstone in the geothermal wellbore, which provides a basis for sand-carrying failure and sand sinking prevention in geothermal wellbore site. [ABSTRACT FROM AUTHOR]

Abstract: Droplets moving at close distances interact hydrodynamically. We present the experimental and theoretical results of a study for monodisperse 73μm geometric diameter droplets with initial velocities between 1.5 and 3m/s and variable generation rate (ranging from 125 to 2000s−1) emitted horizontally and vertically. During the decelerated motion the droplet Reynolds number varied between the value <1 and 10. The hydrodynamic interaction depends on the spatial distance, and we observed a considerable increase of the droplet trajectory endpoints with increasing generation rate. Reviewing the various approaches for the description of hydrodynamic interactions, we adapted a theory for a stationary Stokes flow past a linear array of spheres and found a surprisingly good agreement between our experiments and the above model. Even better agreement was obtained by additionally taking the Basset force into account. [Copyright &y& Elsevier]

Fluidized beds are common in the energy and chemical industries because they provide a good environment for heterogeneous reactions owing to the combination of mixing and multiphase flow hydrodynamics. The hydrodynamics of gas–solid suspensions in fluidized beds is extremely complicated and requires accurate study. A wide range of simulation approaches have been used in fluidized bed design and operational studies, but it is still not clear how the phase interaction should be treated. In this study, a practical characterization method and modeling tool for gas–solid flows are presented, along with a definition of the phase interaction. In this method, the phase interaction is derived for a real solid material with specific particle size, shape and density distributions. In addition, a macroscopic 1D modeling tool for gas–solid flow that is capable of practical stationary and transient simulations is presented. This tool solves the governing equation for the solid-phase momentum and provides physical predictions for transient gas–solid flow investigations. The proposed characterization method and modeling tool are validated against experimental data. • Characterization method for macroscopic gas–solid flow in circulating fluidized bed. • Drag correction for real solid material with size and shape distributions. • Modeling tool to investigate gas–solid flow in fluidized beds with momentum approach. • Modeling tool capable for time-dependent studies for gas–solid flows. [ABSTRACT FROM AUTHOR]