POWDER TECHNOLOGY
·
2024
·
IF 4.5
Mianyan Yang,Zhijun Zhang,Na Wu
The effect of turbulence on the detachment between an air bubble and a glass bead (soda-lime) with different hydrophobicity was comprehensively researched. An experimental apparatus was designed to simulate the turbulent environment during the actual flotation process, which was used to research the detachment of different hydrophobic glass beads from bubble surfaces. It is indicated that three different hydrophobic glass beads detached from the bubble surfaces in the same way but at different speeds. The three-phase contact line (TPCL) shrank rapidly when the centrifugal detachment force of glass beads reached a critical value. The deformation of bubbles increased, and the three-phase contact (TPC) area continuously decreased. When the critical value was exceeded, the sliding and contraction speed around the TPCL further increased until a clear necking phenomena appeared near the TPC. Furthermore, the centrifugal detachment force, capillary force and total pressure force increased with increasing hydrophobicity in the detachment process.
研究领域:
化学工程
·
表面科学
✓ 已验证
产品关联
DOI
高影响因子
Advances in Mechanical Engineering
·
2016
·
IF 0.64
Yue Wang,Wei-Hua Cai,Tong-Zhou Wei,Hong-Na Zhang,Lu Wang,Feng-Chen Li
In this article, the experiments of two-oscillating grid turbulence with viscoelastic fluids were carried out using particle image velocimetry. Two classical drag-reducing additives with viscoelastic characteristics were chosen: polymer (polyacrylamide) and cationic surfactant (cetyltrimethyl ammonium chloride). In order to investigate the viscoelastic effect on coherent structures, proper orthogonal decomposition was performed to identify coherent structures based on particle image velocimetry data. The results show that the minimum number for eigenmodes required for capturing coherent structures, which contains 90% of total turbulent kinetic energy, is 127, 19, and 117 for the Newtonian fluid case, 25 ppm polyacrylamide solution case, and 25 ppm cetyltrimethyl ammonium chloride solution case at grid oscillating frequency f = 7.5 Hz, respectively. It means that coherent structures can be inhibited due to the addition of polyacrylamide additives but not remarkable in 25 ppm cetyltrimethyl ammonium chloride solution case, in other words, the decrease in flow complexity in 25 ppm polyacrylamide solution case. This phenomenon also appears at grid oscillating frequency f = 5 Hz. However, as cetyltrimethyl ammonium chloride solution concentration increases up to 50 ppm, the cetyltrimethyl ammonium chloride solution case shows similar trends as those in 50 ppm polyacrylamide solution case (the number for eigenmodes required for capturing coherent structures is approximate). Therefore, compared with a channel flow with cetyltrimethyl ammonium chloride solution, there exists the larger critical concentration in two-oscillating grid turbulence to show turbulence suppression effect.
研究领域:
流体力学
·
湍流
·
实验流体力学
·
粘弹性
✓ 已验证
产品关联
DOI
高影响因子
WATER RESEARCH
·
2023
·
IF 12.8
Xiaoteng Shen,Hong Huo,Ying Zhang,Yuliang Zhu,Michael Fettweis,Qilong Bi,Byung Joon Lee,Jerome P.-Y. Maa,Qiqing Chen
Biofilm-coated microplastics are omnipresent in aquatic environments, carrying different organic matter (OM) that in turn influences the flocculation and settling of microplastic aggregates. In this study, the effects of chitosan, guar gum, humic acid, and xanthan gum on the flocculation of anthropogenic microplastics are examined under controlled shear through the mixing chamber experiments. The results show that all of the selected OMs have positive effects on biofilm culturing and thus enhance the growth of microplastic flocs, with more evident promoting effects for cationic and neutral OMs (i.e., chitosan and guar gum) than anionic OMs (i.e., humic acid and xanthan). No critical shear rate is observed in the size vs. shear relationship based on our measurements. In addition, the quadrature-based two-class population balance model is employed to track the development of bimodal floc size distributions (FSDs) composed of small and large microplastic flocs. The model predictions show reasonable agreement with the observed FSDs. The largest error of settling flux from the two-class model is 7.8% in contrast with the reference value measured by the camera-based FSDs with 30 bins. This study highlights the role of different OMs on microplastic flocculation and indicates that a two-class model may be sufficient to describe microplastic transport processes in estuaries.
研究领域:
环境科学
·
生态学
✓ 已验证
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2025
·
IF 4.3
Jiaying Lu,Yanqing Guo,Yihang Xin,Xiaogang Yang,Jiusheng Li
Achieving a controllable synthesis of metal nanoparticles depends very much on the hydrodynamics of the synthesis process, in particular the local turbulence that has been considered to have a significant impact on the synthesised nano particle size and morphology. This paper reports the study on turbulence induced shear regulatable synthesis of the silver nanoparticles (AgNPs) using a counter axial-swirling impinging jet flow reactor (CASIJR), exploring the effect of turbulent shear stress on the formation of AgNPs. The micro-mixing and turbulence induced shear in the flow inside the CASIJR reactor were evaluated using Reynolds Average Navier-Stokes (RANS) modelling coupled with the Reynolds Stress Model (RSM). It was indicated from the simulations that an increase in the axial-swirling circular pipe flow diameter based Reynolds number from 3300 to 4900 would enhance the mixing and local turbulence induced shear, characterising by an increase in the mixing index. It was also found from the AgNPs synthesis experiments that there exists a strong correlation between the turbulent shear stress u ′ v ′ ¯ and the synthesised AgNPs size. The average synthesised nano particle size, size distribution, and morphology of AgNPs are affected by the micro-mixing and anisotropic turbulence induced shear in the CASIJR.
研究领域:
化学工程
·
纳米材料科学
✓ 已验证
产品关联
DOI
高影响因子
Membranes
·
2021
·Vol. 11
·期 4
·268
·
IF 4.106
Bin Jiang,Binxing Hu,Na Yang,Luhong Zhang,Yongli Sun,Xiaoming Xiao
Nanofiltration membrane technology is an effective method for secondary treated sewage purification. However, membrane fouling, which is inevitable in the membrane-separation process, can reduce membrane performance and shorten membrane life. Installing a turbulence promoter is a promising means of improving the hydraulic conditions inside the membrane chamber. In this study, the effect of turbulence promoter on prolonging membrane life was studied for the first time. Flat-sheet polyethersulfone nanofiltration membrane was used to filter humic acid solution, used for simulating secondary treated sewage. By comparing photographs and SEM images of the membrane before and after the simulated secondary treated sewage filtration, it was found that humic acid tended to be deposited on the low-velocity region, which was reflected by COMSOL simulation. After incorporating a turbulence promoter, the reduction of the humic acid deposition area and membrane fouling resistance indicated that the turbulence promoter could reduce membrane fouling due to the improved hydraulic conditions. Additionally, the turbulence promoter also increased the flux and reduced the flux decay rate. The turbulence promoter was then place in the crossflow flat-sheet membrane filtration module, and the variation of flux with time was tested in simulated secondary treated sewage with different concentrations. The results showed that the membrane life for the filtration of simulated secondary treated sewage comprising 50, 250, and 500 ppm humic acid increased by 23.1%, 80.4%, and 85.7%, respectively. The results of this article can serve as a reference for the prediction of membrane life and the performance enhancement mechanism of membranes containing a turbulence promoter.Keywords:turbulence promoter;membrane life;COMSOL simulation;sewage treatment;membrane fouling
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
·
2018
·
IF 2.829
Leila Abdoli,Chunhai Guo,Xiuyong Chen,Xiaoyan He,Hua Li
Formation of microbial biofilm on marine structures is crucial for subsequent attachment of macro fouling species and understanding the impact of fluid conditions on formation and growth of the biofilm is essential for preventing biofouling. Here we report the effect of shear stresses generated by laminar and weakly turbulent flow on the adhesion of typical marine bacterium Bacillus sp. biofilm on stainless steel . Numerical simulation was carried out to calculate the distribution of pressure and shear stress applied on adhered bacteria. The shear stress was proportional to both the distance from the center of rotating disk and rotation speed. The stress reached 18 Pa as the flow velocity was 2.4 m/s and the rotation speed was 600 rpm. Further adhesion testing revealed that development of the bacterial biofilm in early stage was unaffected by the shear stresses. However, shear stress regulated the adherence orientations of the bacteria on the steel surface. Turbulent flow obviously shaped development of the architecture of the biofilm, as revealed by CLSM and SEM characterization. Biofilm growth patterns were clearly observed under weakly turbulent flow, however, they were not seen under laminar flow . The microcolonies assumed elongated forms, possibly triggered by exerted pressure drag force. The results give insights into possibly controlling the formation of marine biofilm on marine infrastructures for desired antifouling performances.
研究领域:
微生物学
·
海洋科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
ACTA ASTRONAUTICA
·
2022
·
IF 2.954
Wenli Yu,Weixing Zhou,Zhenjian Jia,Zhixiong Han
The regenerative cooling technique with endothermic reactions is prospective for scramjet engines, in which the convective heat transfer characteristics are necessary for the thermal system design. In this work, the turbulent heat transfer characteristics of hydrocarbon fuels with endothermic chemical reactions were experimentally and numerically investigated. Three kinds of surrogates and two different pressures were employed to obtain various chemical endotherms, and the distributions of physical properties and dimensionless parameters were analyzed in the chemical region. Results showed that endothermic chemical reactions improved the convective heat transfer performance, even though the variations of fluid Reynolds number and Prandtl number brought by chemistry were small. Then, a dimensionless parameter was proposed to describe the proportion of chemical endotherm capacity. The numerical results revealed that the natural logarithm of Nusselt number enhancement changed linearly with the proposed dimensionless parameter, and the slopes were irrelevant to reactant types or chemical conditions. Last, by modifying the Dittus-Boelter correlation, a novel Nusselt number correlation was put forward for the endothermic reacting flow. Based on the analysis of the existing data and the formula form, continuously increasing the fuel chemical endotherm might bring a smaller benefit of Nusselt number augmentation.
研究领域:
航空航天工程
·
热能工程
·
化学工程
✓ 已验证
DOI
高影响因子
POWDER TECHNOLOGY
·
2025
·
IF 4.6
Mianyan Yang,Zhijun Zhang
The critical flow velocity required to detach glass beads (soda-lime) of different hydrophobicity from bubbles was investigated. Using a home-made turbulence controlling system to observe the centrifugal motion of glass beads. The results indicated that different flow velocities were achieved by controlling the rotational speed. Different flow velocity indirectly affected the centrifugal acceleration when the centrifugal detachment of glass beads occurred. When the flow velocity exceeded the critical value, the different hydrophobic glass beads and bubble aggregates experienced centrifugal detachment force also reached the critical value. Due to the pinning effect, the more hydrophobic the glass beads attached to the bubbles, the more stable the aggregates formed. It was necessary to increase the flow velocity to enhance the centrifugal detachment force. The three-phase contact line (TPCL) between glass beads and bubbles rapidly slipped and contracted when attachment force was less than detachment force in centrifugal motion. Resulting in a noticeable necking phenomenon that completed the detachment. Meanwhile, the detachment behavior between glass beads and bubbles did not occur at specific locations, but rather randomly. It was depended on the size and strength of the vortex at that location, as well as the stability of attachment between bubbles and various glass beads.
研究领域:
流体力学
·
界面科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Omega
·
2021
·
IF 3.512
Xiang-lan Ming,Ruizi Wang,Teng Li,Xixi Wu,Liang-jie Yuan,Yu Zhao
The micro–nano-structured FePO4·2H2O was prepared from mixed solution of FeSO4 oxidized in diluted H3PO4 with H2O2 and NaOH solution in the turbulent flow cycle state at 90 °C. The resulting products were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Constant current charge/discharge tests were adopted to investigate the electrochemical performance and the rate capability (from 0.1C to 5C) of the carbon-coated LiFePO4 composite materials prepared from the micro–nano-structured FePO4. The carbon-coated LiFePO4 composite materials deliver a high specific discharge capacity of 153.7 mAh·g–1, exhibit excellent cycle performance with 98.6% of the capacity retained after 30 cycles. This study demonstrates that the turbulent flow cycle method may be an economical and effective method for industrial production of fine and uniform micro–nano-structured FePO4·2H2O particles for LiFePO4 cathode materials for Li-ion batteries.
研究领域:
材料科学
·
电化学
·
能源存储
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Environmental Chemical Engineering
·
2024
·
IF 7.4
Zhewen Shao,Kexin Xiang,Shuchang Liu,Feng Hong,Ye Gao,Enhong Lei,Jinping Jia,Yingping Huang
Presently, fast degradation of organic wastewater has been achieved by the synergetic method of hydrodynamic cavitation and H2O2 at a laboratory scale, while the physico-chemical effect, especially the turbulence characteristics on the degradation process remains lacking. This paper presents investigation on the degradation of dyeing wastewater containing methylene blue (MB) under neutral condition, within a vortex-based hydrodynamic cavitation (VBHC) reactor. Operating conditions are firstly optimized and then used to collaborate with H2O2 to study the synergetic effects of this hybrid treatment method. The turbulence characteristics are subsequently obtained by a computational fluid dynamics (CFD) simulation, and the correlation between them and the degradation process of MB is revealed. The results indicate that the highest degradation rate of 91.95 % is achieved under optimal conditions. Higher inlet pressure (4.5 bar) owns the thickest vapor volume fraction, greatest vapor transfer rate, and largest size of cloud cavity in the vortex core region, indicating the strongest cavitation intensity; meanwhile, moderate solution temperature (30 ℃) also favors for the greatest cavitation intensity inside the reactor. The optimal cavitation intensity activates the considerable production of reactive oxygen species, and results in good consistency with the MB degradation performance, which predominately occurs in the annular region around the vortex rope. This research unveils the rationale behind the physical essences of the VBHC process and its influence on the degradation efficacy of MB, which can provide reliable guidance for further development of cavitational reactors to degrade organic pollutants by the VBHC/H2O2 hybrid treatment method.
研究领域:
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
IEEE SENSORS JOURNAL
·
2024
·Vol. 24
·期 5
·5895-5903
·
IF 4.3
Pang Peng,Zhang Tao,Zhang Xingxu,Ma Binghe,Zhao Keli,Deng Jinjun,Luo Jian
Wall shear stress and flow direction provide a basis for analyzing the boundary layer conditions, investigating drag reduction mechanisms, and enhancing environmental perception. This work presents novel single-loop and dual-loop hot-film sensors driven by the constant temperature (CT), which are capable of simultaneously measuring wall shear stress and flow direction. Based on the heat transfer and fluid dynamics theory, a mathematical model is developed to analyze the flow directions. The sensors feature multilayer structures, where the numerous leads are concealed and embedded in the insulation layer to enhance their robustness and integration. Utilizing the microelectromechanical system technology, sensor prototypes with single-loop and double-loop are fabricated. In particular, a new process method for accomplishing junction holes in the polyimide (PI) insulation layer is proposed. The sidewall-to-bottom angle of junction holes fabricated through wet etching is ~29.4°. After metal lays are deposited in the junction holes, the upper and bottom surfaces of the insulation layer are able to conduct electricity. Moreover, a testing system consisting of a microchannel and a turbulence generator is established to carry out the experimental verification. Then, the hot-film sensors are tested in the microchannel with a maximum Reynolds number of Red = 8600. Low-frequency turbulence as well as natural transition signals are detected by the hot-film sensors successfully. In the range of wall shear stress from 0 to 14.2 Pa, the accuracies of the dual-loop and single-loop hot-film sensors in perceiving flow directions are better than ±3° and ±6.5°, respectively. This work assists to analyze the boundary layer states, to investigate drag reduction mechanisms, and to enhance environmental perception in flow field.
研究领域:
流体力学
·
传感器技术
·
环境感知
·
微制造技术
✓ 已验证
DOI
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2025
·
IF 9
Qing Sun,Lifang Zhang,Fengjun Ming,Jiawei Fang,Weidong Zhang
Amine-based chemical absorption for CO 2 capture gains superiorities in removal efficiency, CO 2 capacity and selectivity, but suffering from high energy consumption. Improvements on absorption – desorption performances could effectively tackle the regeneration energy and capital cost challenge. Recently, a new method of mass transfer promoters (MTPs) based on density-triggered interfacial turbulence has been proposed and confirmed to increase mass transfer rate by several fold. Guided by density difference principle, in this work, means of adjusting amine type, concentration and MTPs were investigated to regulate the absorption − desorption rate. Increasing amino group of amine molecule, amine concentration and MTPs concentration were found to enhance absorption rate by 5–7 fold resulted from the strengthening of density difference. The visualized experiments revealed the transition and reinforcement of interfacial turbulence driven by intensified density difference. Further the power function relationship between enhancement factor and parameters related with density driven Rayleigh-Bénard effect was established, providing guidance of predicting enhancement extent. The effects of MTPs on desorption performance were assessed in terms of desorption rate and cyclic CO 2 loading. Absorbents with MTPs possessed higher desorption rate and cyclic CO 2 loading with largest enhancement of 154 % and 159 % respectively, showing great potential for cost-effective CO 2 capture.
研究领域:
化学工程
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）