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The present study proposes a simple mass-micromanipulation method for tiny particles by expanding our previous finding that submillimeter-scale particles scattered at the bottom of a water-filled rectangular container align at specific positions when the particles are subject to standing waves induced by lateral oscillations of the container at specific frequencies. First, this unique phenomenon (termed as the particle alignment phenomenon in the present study) was examined, focusing on the distance from the bottom of the container, oscillation amplitude, and liquid height in order to further reveal the underlying mechanism. The main findings obtained through several simulations and experiments were that the modulation of oscillation amplitude affected the behavior of particles at the bottom of the container related to the alignment precision and that the proper control of liquid height allowed the production of different particle alignment phenomena even if the same lateral oscillation was applied to the container. Additionally, using these new findings, we succeeded in forming different numbers of particle lines in multiple containers, which were set at different liquid heights, placed on an oscillation stage. Based on the results, this paper discusses possible mass micromanipulations using the particle alignment phenomenon. [ABSTRACT FROM AUTHOR]

In a cylindrical laboratory reactor, in which a biofilm was grown on a gas-permeable silicone membrane tubing through which oxygen was supplied, the removal of xylene from the bulk fluid was investigated. Two days after starting the experiment 98 % of xylene was degraded and was no longer transferred into the gas phase. Using polarographic microelectrodes the thickness of the biofilm and the boundary layer as well as the oxygen profiles in both layers have been measured. The fluid velocity had three major influences: it affected the boundary layer thickness, the biofilm density and the sloughing of the biofilm. At higher fluid velocities (Reynolds numbers) high oxygen consumption within the biofilm could be quantified. At these higher fluid velocities the biofilm was grown with a higher density and adhered better to the membrane. By application of higher oxygen partial pressures in the gas phase and higher fluid velocities in the liquid phase, the mean degradation efficiency was increased from 38 to 96 %. A computer simulation showed good correspondence with the experimental investigations and allowed a total process analysis. Membrane-biofilm reactors are preferred for technical applications as, e. g., treatment of landfill leachates with high contents of volatile organics. [ABSTRACT FROM AUTHOR]

In the present work, we obtained explicit formulas that relate permeability to porosity and specific surface area of pores and cracks. We show that Darcy's law is not an obligatory condition for the determination of fluid flow velocity; this empirical law may be true for some geometry of grains and pores, and maybe not valid for another geometry with flowing conditions. The role of permeability is played by the ratio of porosity (to the third power) to the specific surface area (to the second power) of pores or cracks. Fluid flow velocity depends on porosity, specific surface area, viscosity, and borehole radius. The analog of Darcy's law can be calculated using integral geometry parameters and boundary conditions; i. e., it does not have to be only empirical, but it is also an analytical law. The dependence of permeability on porosity differs significantly from enough big to small porous media. The fluid flow can be calculated using the elastic equilibrium equations and the incompressibility of viscous fluid without any phenomenological parameters. One of the main result of the paper is the dependence of the fluid flow velocity on porosity, specific surface area, viscosity, borehole radius, that is valid only for infinite clusters of porous and cracks. For a real rock sample, there are dead-end tracks, where the fluid flow is equal to zero. The infinite cluster is a system without dead-end tracks, and the model is valid for all reservoir volume. For real clusters, it is necessary to take into account the existence of dead-end tracks, which is possible to model with some probability function related to porosity. The analog of Darcy's law can be calculated using integral geometry parameters and boundary conditions; i. e., it can be not only empirical but analytical law. The dependence of permeability on porosity differs significantly from enough big to small porous media. The fluid flow can be calculated using the elastic equilibrium equations and the incompressibility of viscous fluid, but there are some cases where Darcy's law is not valid. The figure shows the relationship between permeability (k , vertical coordinate), porosity (x -axes) and specific surface area (y -axes) displaying the relative fast decays. [Display omitted] • The model of structured continuum connects friction forces with SSA and porosity. • Fluid flow depends on the discontinuity between the pressure in solid and in liquid. • Permeability depends on the porosity and specific surface area of pores and cracks. • Darcy's law is not necessarily true for all geometries of grains and pores. [ABSTRACT FROM AUTHOR]

The ITER facility is an international research project that is under construction in Cadarache, France. US ITER is responsible for the design, engineering, and procurement of the Tokamak Cooling Water System (TCWS). TCWS piping size varies from DN40 to DN500. A design guideline specifies that piping smaller than DN150 must have a fluid velocity below 6 m/s, while a fluid velocity of up to 9 m/s is permitted for piping larger than DN150. Fluid velocity affects pipe size, pressure drop, pump size, piping support, etc. Factors considered when determining maximum allowable fluid velocity include erosion and corrosion, pump capacity, cavitation, hydrodynamic instability, and actual nuclear plant experience. The previous study performed to support the ITER piping design indicated that the hydrodynamic instability was a reason to limit maximum allowable fluid velocity below 6 m/s regardless of the piping size. However, the later study found that, when properly supported, pipe buckling and fluttering from hydrodynamic force would not cause instability. Instead, cavitation erosion—a pipeline phenomenon that forms vapor cavities in pipe—may limit allowable fluid velocity. Cavitation is a pipeline phenomenon that forms vapor cavities, which then go unstable and collapse violently in low-pressure, turbulent, flow-separation regions inside valves, elbows, pipe expansions, and other fluid handling components. Considering the cavitation issue, pressure drop, and a typical practice in a nuclear plant system, fluid velocity is to limit below 6 m/s for piping smaller than DN150 and 9 m/s for piping larger than DN150. This paper describes a hydraulic stability analysis, the fluid velocity generally accepted in nuclear plants and the cavitation-erosion limit in fluid velocity. [ABSTRACT FROM AUTHOR]

The determination of fluid velocity and its movement implicate sensitive measurement procedures that allow, when associated with other system physical variables, the calculation of the fluid-mechanical characteristic parameters, or allow characterizing the particles suspended in the fluid and eventually to calculate their concentration and pollution effects. The possibility of optical methods opened with the availability of small and accessible lasers and fast optoelectronic systems for detection and data processing. This paper presents a Laser Doppler anemometry system for fluid measurements in 1D, configurated as a Doppler differential system, suitable to measure the effects of very low particle density, with an electronic system for signal detection and processing, able to work with the electric signal delivered by a photomultiplier tube RCA 931A, which is amplified and filtered for later analysis on a PC. By analysing the signal, it is possible to determine the changes in the Doppler frequency of the scattered light; with this information one of the particle velocity components can be determinated. Sequencial measurements allow obtaining the fluid speed profiles. Typical speed profile of water flowing through a circular cross-section tube is presented. [ABSTRACT FROM AUTHOR]

Droplet–based microfluidic assisted devices have proposed an extensive interest in many applications such as lab-on-a-chip technologies as well as chemical/biological/nanomaterial preparation, chemical engineering, drug delivery, tissue engineering and biosensing. Here, a computational fluid dynamic model was developed for deep understanding of the droplet size and formation in a flow-focusing (FF) microchannel with consideration of the continuous phase (non–Newtonian fluid). The simulations presented an alternative method to achieve insights into this complicated process. In the following for the first time, the role of channel geometry, channel aspect ratio and flow rate ratio on droplet features including the mechanism of droplet formation, diameter/volume of droplet, velocity/amount of droplet formation, and final shape/size of the generated droplets were fully described. These findings could remarkably derive desirable protocols to control droplets characteristics comprising their size and shape in non–Newtonian fluids. Moreover, level set (LS) method was used for scrutinizing the droplet-breaking procedure in the microfluidic FF devices. The results showed that different droplet sizes could be prepared with changing the various parameters, demonstrating many challenges in various applications including lab-on-a-chip, cell encapsulation, drug delivery, tissue engineering, biosensing and bioimaging could be successfully addressed. • A computational fluid dynamic model was developed for deep understanding of the droplet size and formation in a flow-focusing (FF) microchannel. • The simulations presented an alternative method to achieve insights into this complicated process. • For the first time, the role of channel geometry, channel aspect ratio and flow rate ratio on droplet features were fully described. • Level set (LS) method was used for scrutinizing the droplet-breaking procedure in the microfluidic FF devices. • Experimental validation was established for 2 devices that the results corroborated the simulation outcomes successfully. [ABSTRACT FROM AUTHOR]

At present, autonomous underwater vehicles (AUVs) cannot perceive local environments in complex marine environments, where fish can obtain hydrodynamic information about the surrounding environment through a lateral line. Inspired by this biological function, an artificial lateral line system (ALLS) was built on a moving bionic carrier using the pressure sensor in this paper. When the carrier operated with different speeds in the flow field, the pressure distribution characteristics surrounding the carrier were analyzed by numerical simulation, where the effect of the flow angle between the fluid velocity direction and the carrier navigation direction was considered. The flume experiment was carried out in accordance with the simulation conditions, and the analysis results of the experiment were consistent with those in the simulation. The relationship between pressure and fluid velocity was established by a fitting method. Subsequently, the pressure difference method was investigated to establish a relationship model between the pressure difference on both sides of the carrier and the flow angle. Finally, a back propagation neural network model was used to predict the fluid velocity, flow angle, and carrier speed successfully in the unknown fluid environment. The local fluid environment perception by moving carrier carrying ALLS was studied which may promote the engineering application of the artificial lateral line in the local perception, positioning, and navigation on AUVs. [ABSTRACT FROM AUTHOR]

The 11α-hydroxylation of canrenone can be catalyzed by Aspergillus ochraceus in bioreactors, where the geometry of the impeller greatly influences the biotransformation. In this study, the effects of the blade number and impeller diameter of a Rushton turbine on the 11α-hydroxylation of canrenone were considered. The results of fermentation experiments using a 50 mm four-blade impeller showed that 3.40% and 11.43% increases in the conversion ratio were achieved by increasing the blade number and impeller diameter, respectively. However, with an impeller diameter of 60 mm, the conversion ratio with a six-blade impeller was 14.42% lower than that with a four-blade impeller. Data from cold model experiments with a large-diameter six-blade impeller indicated that the serious leakage of inclusions and a 22.08% enzyme activity retention led to a low conversion ratio. Numerical simulations suggested that there was good gas distribution and high fluid flow velocity when the fluid was stirred by large-diameter impellers, resulting in a high dissolved oxygen content and good bulk circulation, which positively affected hyphal growth and metabolism. However, a large-diameter six-blade impeller created overly high shear compared to a large-diameter four-blade impeller, thereby decreasing the conversion ratio. The average shear rates of the former and latter cases were 43.25 s -1 and 35.31 s -1 , respectively. We therefore concluded that appropriate shear should be applied in the 11α-hydroxylation of canrenone. Overall, this study provides basic data for the scaled-up production of 11α-hydroxycanrenone.

Objective: This study aimed to examine the irrigant flow generated by laser-activated irrigation (LAI), in comparison with ultrasonic-activated irrigation (UAI) and syringe irrigation (SI), in the area beyond the ledge using particle image velocimetry (PIV). Background data: There was no reported study about cleaning efficacy of LAI beyond the ledge. Materials and m ethods: Forty-nine J-shaped root canal models (40° curvature) were instrumented to no. 35/0.06, and a ledge, 2.5 mm deep, was created with no. 60/0.08 instrument at 5 mm from the apical foramen in each canal. The samples were irrigated with LAI [30 mJ/5 pulse per second (pps), 30 mJ/10 pps, 30 mJ/20 pps, 50 mJ/10 pps, 70 mJ/10 pps], UAI, and SI with a tip/needle insertion depth of 5 mm from the apical foramen ( n  = 7). PIV was performed with glass beads and a high-speed camera. Velocities were compared in the coronal and apical areas to the ledge, respectively. Results: In the apical area, all LAI groups and UAI produced a higher velocity than that of SI, and LAI at 30 mJ/20 pps and 70 mJ/10 pps showed significantly higher velocity than that of UAI ( p  < 0.05). In the coronal area, LAI at 30 mJ/20 pps generated a significantly higher velocity than that of UAI and SI ( p  < 0.05). Velocity was significantly slower in the apical area than in the coronal area in UAI and SI ( p  < 0.05), but was similar between both areas in LAI except at 30 mJ/20 pps. Conclusions: Among tested laser settings, higher velocity was significantly achieved by LAI at 30 mJ/20 pps and 70 mJ/10 pps compared with UAI in the canal area beyond the ledge. SI generated lower fluid movement than LAI and UAI in both canal regions.

Atmospheric pressure chemical vapor deposition (APCVD) has been used extensively for synthesizing two-dimensional (2D) materials because of its low cost and promise for high-quality monolayer crystal synthesis. However, the understanding of the reaction mechanism and the key parameters affecting the APCVD processes is still in its embryonic stage. Hence, the scalability of the APCVD method in achieving large-scale continuous film remains very poor. Here, we use MoSe 2 as a model system and present a fluid guided growth strategy for understanding and controlling the growth of 2D materials. Through the integration of experiment and computational fluid dynamics (CFD) analysis in the full-reactor scale, we identified three key parameters, precursor mixing, fluid velocity, and shear stress, which play a critical role in the APCVD process. By modifying the geometry of the growth setup to enhance precursor mixing and decrease nearby velocity shear rate and adjusting flow direction, we have successfully obtained inch-scale monolayer MoSe 2 . This unprecedented success of achieving scalable 2D materials through fluidic design lays the foundation for designing new CVD systems to achieve the scalable synthesis of nanomaterials.

A computational fluid dynamics (CFD) model of the fluid velocities generated by the agitation system of an air-assisted sprayer was developed and validated by practical experiments in a laboratory. The model was developed considering different settings of the agitation system: Three water levels in the tank (1000, 2000, and 3000 L); two different numbers of active nozzles (2 or 4); and three working pressures of the agitation circuit (8, 10, or 12 bar). Actual measurements of the fluid velocity into the tank were taken using an acoustic Doppler velocimeter (ADV). CFD simulations made it possible to estimate fluid velocities at 38% of the measuring points with relative errors of less than 30%. Additionally, the CFD models have allowed the correct prediction of the general behavior of the fluid in the tank considering mean velocities depending on the setting parameters of the agitation system (water level in the tank, hydraulic circuit pressure, and number of active nozzles). [ABSTRACT FROM AUTHOR]

An acoustic Doppler velocimeter (ADV) was used to analyse the impact of an agricultural sprayer's agitation system settings on fluid velocities inside the tank. A 3000 L capacity sprayer equipped with a 4-nozzle hydraulic agitation system was used. ADV measurements were carried at 32 points inside the tank under the following settings: circuit pressures of 8, 10, or 12 bar; water level in the tank of 1000, 2000, or 3000 L; 2 or 4 active nozzles. An agitation test with a concentration of 0.4% copper oxychloride was employed to analyse the concentration of active matter as a function of tank fill level and number of active nozzles. All parameters significantly affected the fluid velocity, which increased with increasing pressure, but decreased with increasing water level in the tank and an increased number of active nozzles. Concentration tests showed greater active matter concentrations when higher velocities were recorded by the ADV. The ADV was shown to be a useful tool for the rapid assessment of fluid velocities; in the future, it could be used to validate the design of agitation systems, and to estimate their capacity to ensure an adequate level of active matter concentration in the fluid. [ABSTRACT FROM AUTHOR]

Rapid prototyping techniques have been widely used in tissue engineering to fabricate scaffolds with controlled architecture. Despite the ability of these techniques to fabricate regular structures, the consistency with which these regular structures are produced throughout the scaffold and from one scaffold to another needs to be quantified. Small variations at the pore level can affect the local mechanical stimuli sensed by the cells thereby affecting the final tissue properties. Most studies assume rapid prototyping scaffolds as regular structures without quantifying the local mechanical stimuli at the cell level. In this study, a computational method using a micro-computed tomography-based scaffold geometry was developed to characterize the mechanical stimuli within a real scaffold at the pore level. Five samples from a commercial polycaprolactone scaffold were analysed and computational fluid dynamics analyses were created to compare local velocity and shear stress values at the same scaffold location. The five samples did not replicate the computer-aided design (CAD) scaffold and velocity and shear stress values were up to five times higher than the ones calculated in the CAD scaffold. In addition high variability among samples was found: at the same location velocity and shear stress values could be up to two times higher from sample to sample. This study shows that regular scaffolds need to be thoroughly analysed in order to quantify real cell mechanical stimuli so inspection methods should be included as part of the fabrication process.