A Comparative Study of the Immscible Density Currents Using the SPH And VOF-LES Methods

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Improvement of Secondary Sedimentation Tanks in the Presence of a Baffle

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Numerical simulation of turbidity current using V2-f turbulence model

The deposition behavior of fine sediment is an important phenomenon, and yet unclear to engineers concerned about reservoir sedimentation. An elliptic relaxation turbulence model ( 2 n - f model) has been used to simulate the motion of turbid density currents laden with fine solid particles. During the last few years, the 2 n - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. The 2 n - f model has also proved to be superior to other RANS (Reynolds-Averaged Navier-Stokes) methods in many fluid flows where complex flow features are present. This current becomes turbulent at low Reynolds number (order 1000). The k -e model, which was standardized for high Reynolds number and isotropic turbulence flow, cannot simulate the anisotropy and nonhomogenous behavior near the wall. In this study, the turbidity current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been validated by available experimental data sets. Moreover, results have been compared with the standard k -e turbulence model. The deposition of particles and the effects of their fall velocity on concentration distribution, Richardson number, and the deposition rate are also investigated. The results show that the coarse particles settle rapidly and make the deposition rate higher

Study of the increase in phytoremediation efficiency in a nickel polluted soil by the usage of native bacteria: Bacillus safensis FO.036b and Micrococcus roseus M2

Nickel (Ni) is a heavy metal and soil pollutant but existence of small amount of it as a metallic part of urease enzyme in the plants is necessary. Remediation of spots contaminated with heavy metals is particularly challenging. Phytoremediation, the use of plants for environmental restoration, is a novel clean up technology. In this study, five levels of nickel [control (Ni0), Ni125, Ni250, Ni500 and Ni1000 (mg kg-١ )] as nickel chloride (NiCl2.6H2O) and three levels of bacterial inoculants [control (B0), Bacillus safensis FO.036b (B1) and Micrococcus roseus M2 (B2)] were used in sunflower (Helianthus annus), amaranthus (Amaranthus retroflexus) and alfalfa (Medicago sativa) for phytoextraction of nickel. A factorial experiment with a randomized complete block design (RCBD) with three replications was used. Results demonstrated that by increasing the nickel concentration in soil, its absorption by the plants has increased significantly. The highest concentration of nickel was found in shoot of amaranthus (176.83 mg kg-1) and in the root of plants, in alfalfa (462.73 mg kg-1) by usage of inoculant (P<0.05). The highest absorption of nickel occurred with B1 inoculant in amaranthus, which was 459.41 µgPot-1. Applying this inoculant may also cause an increase in concentration of iron and zinc in the root and shoot of the plants

Novel approaches in cancer management with circulating tumor cell clusters

© 2019 The Authors Tumor metastasis is responsible for the vast majority of cancer-associated morbidities and mortalities. Recent studies have disclosed the higher metastatic potential of circulating tumor cell (CTC) clusters than single CTCs. Despite long-term study on metastasis, the characterizations of its most potent cellular drivers, i.e., CTC clusters have only recently been investigated. The analysis of CTC clusters offers new intuitions into the mechanism of tumor metastasis and can lead to the development of cancer diagnosis and prognosis, drug screening, detection of gene mutations, and anti-metastatic therapeutics. In recent years, considerable attention has been dedicated to the development of efficient methods to separate CTC clusters from the patients’ blood, mainly through micro technologies based on biological and physical principles. In this review, we summarize recent developments in CTC clusters with a particular emphasis on passive separation methods that specifically have been developed for CTC clusters or have the potential for CTC cluster separation. Methods such as liquid biopsy are of paramount importance for commercialized healthcare settings. Furthermore, the role of CTC clusters in metastasis, their physical and biological characteristics, clinical applications and current challenges of this biomarker are thoroughly discussed. The current review can shed light on the development of more efficient CTC cluster separation method that will enhance the pivotal understanding of the metastatic process and may be practical in contriving new strategies to control and suppress cancer and metastasis

Experimental Investigation of Turbulence Specifications of Turbidity Currents

The present study investigates the turbulence characteristic of turbidity current experimentally. The three-dimensional Acoustic-Doppler Velocimeter (ADV) was used to measure the instantaneous velocity and characteristics of the turbulent flow. The experiments were conducted in a three-dimensional channel for different discharge flows, concentrations, and bed slopes. Results are expressed at various distances from the inlet, for all flow rates, slopes and concentrations as the distribution of turbulence energy, Reynolds stress and the turbulent intensity. It was concluded that the maximum turbulence intensity happens in both the interface and near the wall. Also, it was observed that the turbulence intensity reaches its minimum where maximum velocity occurs

Experimental and Numerical Simulation of the Effect of Particles on Flow Structures in Secondary Sedimentation Tanks

Sedimentation tanks are designed for removal of floating solids in water flowing through the water treatment plants. These tanks are one of the most important parts of water treatment plants and their performance directly affects the functionality of these systems. Flow pattern has an important role in the design and performance improvement of sedimentation tanks. In this work, an experimental study of particle-laden flow in a rectangular sedimentation tank has been performed. Kaolin was used as solid particles in these experiments. Also, a numerical simulation was developed using the finite volume method with a k-ε turbulent model. The results of the numerical model agree well with the experimental data. Hydrodynamic parameters and flow patterns of the fresh water flow and particle-laden flow are also compared in this study. The results show that the existence of particles completely changes the flow structures. It seems that the main reason for this phenomenon is the particles settling. Our experimental observations and numerical results show that parameters such as the maximum streamwise velocity, fully developed location, shear stress coefficient at the bottom of the tank and so on are different in water-containing particles compared to pure water and the inlet concentration strongly intensifies the differences

Determination of Settling Tanks Performance Using an Eulerian- Lagrangian Method

Circulation regions always exist in settling tanks. These regions reduce the tank’s performance and decrease its effective volume. The recirculation zones would result in short-circuiting and high flow mixing problems. The inlet position would also affect the size and location of the recirculation region. Using a proper baffle configuration could substantially increase the performance of the settling tanks. A common procedure for the comparison of the performances of different tanks has been using the Flow Through Curves (FTC) method. FTC, however, neglects tendencies for particles sedimentation. In this work, a new method for evaluation of the settling tanks performance is presented. The new method which is referred to as the particle Tracking Method (PTM) is based on an Eulerian-Lagrangian approach. In this paper, by using FTC and PTM the effects of the inlet position and the baffle configuration on the hydraulic performance of the primary settling tanks were studied and results were compared. Then, shortcomings of the FTC approach were stated. The optimal positioning of the baffles was also determined though a series of computer simulations

Subthreshold and near-threshold kaon and antikaon production in proton-nucleus reactions

The differential production cross sections of K^+ and K^- mesons have been measured at the ITEP proton synchrotron in p+Be, p+Cu collisions under lab angle of 10.5^0, respectively, at 1.7 and 2.25, 2.4 GeV beam energies. A detailed comparison of these data with the results of calculations within an appropriate folding model for incoherent primary proton-nucleon, secondary pion-nucleon kaon and antikaon production processes and processes associated with the creation of antikaons via the decay of intermediate phi mesons is given. We show that the strangeness exchange process YN->NNK^- gives a small contribution to the antikaon yield in the kinematics of the performed experiment. We argue that in the case when antikaon production processes are dominated by the channels with KK^- in the final state, the cross sections of the corresponding reactions are weakly influenced by the in-medium kaon and antikaon mean fields.Comment: 24 pages. accepted for publication at J.Phys.

Spheroids-on-a-chip: Recent advances and design considerations in microfluidic platforms for spheroid formation and culture

© 2018 Elsevier B.V. A cell spheroid is a three-dimensional (3D) aggregation of cells. Synthetic, in-vitro spheroids provide similar metabolism, proliferation, and species concentration gradients to those found in-vivo. For instance, cancer cell spheroids have been demonstrated to mimic in-vivo tumor microenvironments, and are thus suitable for in-vitro drug screening. The first part of this paper discusses the latest microfluidic designs for spheroid formation and culture, comparing their strategies and efficacy. The most recent microfluidic techniques for spheroid formation utilize emulsion, microwells, U-shaped microstructures, or digital microfluidics. The engineering aspects underpinning spheroid formation in these microfluidic devices are therefore considered. In the second part of this paper, design considerations for microfluidic spheroid formation chips and microfluidic spheroid culture chips (μSFCs and μSCCs) are evaluated with regard to key parameters affecting spheroid formation, including shear stress, spheroid diameter, culture medium delivery and flow rate. This review is intended to benefit the microfluidics community by contributing to improved design and engineering of microfluidic chips capable of forming and/or culturing three-dimensional cell spheroids